late neogene fluvial stratigraphy of texas coastal plain

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I I I I I I I I . I I Lubbock Lake Landmark Quaternary Research Center Series 4 GUIDEBOOK 10th Annual Meeting South-Central Friends of the Pleistocene LATE CENOZOIC ALLUVIAL STRATIGRAPHY AND PREHISTORY OF THE INNER GULF COASTAL PLAIN, SOUTH-CENTRAL TEXAS LATE PREHISTORIC 1110 111··-· •••• ,. : ,:: L ....-::=:::Jl>, D.P. LEONCREEXPA.l.EOSOl. LATE ARCHAIC -,. 4.135:t,70 8.P. I MEDINA PALEOSOL I \ \ .. ,S70.±,70 D.P. .-- EAR!.V "Rl'IIAIC 6,450±,lJO B.P. , ' '. 6.930.±,65 B.P. LATEPALEOINDIAN ,.. 780:,2108 P: /-, i f j"ur'"!""('.,.'rTh u\ I .• 9,200.±,lJO 8.P ................ 9, 780.:t,IlO B.. .. I i :870:t,120 MOOERNA...OODPLAIN .• I ··I··-... - .. ! SOMERSETPAI..BlSlX.. 9 800±,140 B.P. \ PEJlEZ'AlEOSOl PEJl.EZPAlfOS(H.. SUI,ifled Gruel, Ind S,n<b .' I \ I I 0 70 n n 10,781):140 B.P. .••• 1,41 ±. .r. ........ \ '-- MEDlNA"IVElI 1'10 .. ··---,S'Ori,i,L:.:::i,------,-.·· _. 13,480:t,J60 B.P. '-lO,08 0:t.S60 B.P. '1 ',,"',. .. -----------'L:.:.::,-'SOiL'1'-'. 13,640:,210 B.P. " -', SOILI B.P. 15,270%,170 B.P. SlIalifitd Grhtb Illd SllIdo ..- ,- ,w. i - 400.. JOO.. . 0 Richard Beene Site (41BX83l) San Antonio, Texas March 27-29, 1992

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PDF version of:Mandel, R. D., and S. C. Caran, eds., 1996, Late Cenozoic AlluvialStratigraphy of the Inner Gulf Coastal Plain, South-Central. Texas.Guidebook of the 10th Annual Meeting South-Central Friends of the Pleistocene, San Antonio, Texas, March 27-29, 1992.

TRANSCRIPT

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Lubbock Lake Landmark Quaternary Research Center Series 4

GUIDEBOOK 10th Annual Meeting

South-Central Friends of the Pleistocene

LATE CENOZOIC ALLUVIAL STRATIGRAPHY AND PREHISTORY OF THE INNER GULF COASTAL

PLAIN, SOUTH-CENTRAL TEXAS

LATE PREHISTORIC

1110 111··-· •••• ,. : ,:: L ....-::=:::Jl>, ~J.090±'70 D.P. LEONCREEXPA.l.EOSOl. LATE ARCHAIC

"tlDOLE~CHAIC -,. 4.135:t,70 8.P. I MEDINA PALEOSOL ~ I \ \ .. ,S70.±,70 D.P.

.-- EAR!.V "Rl'IIAIC '::::J'-'I~ 6,450±,lJO B.P. , ' '. 6.930.±,65 B.P.

f,-~'. LATEPALEOINDIAN ,.. .~8 780:,2108 P: /-, ~VEl.M·C1I.EEJ(PALBJ5Ot.i i f j"ur'"!""('.,.'rTh u\ I .• 9,200.±,lJO 8.P •

................ ~ 9, 780.:t,IlO B.. .. I

i :870:t,120 B.P:~ MOOERNA...OODPLAIN .• I ··I··-... - .. _~r··T ! SOMERSETPAI..BlSlX.. 9 800±,140 B.P.

\ PEJlEZ'AlEOSOl PEJl.EZPAlfOS(H.. ~ SUI,ifled Gruel, Ind S,n<b .' I \ I I 0 70 n n 10,781):140 B.P. • .••• 1,41 ±. .r.

........ \ '-- MEDlNA"IVElI

1'10 ..

··---,S'Ori,i,L:.:::i,------,-.·· _. 13,480:t,J60 B.P. '-lO,080:t.S60 B.P. '1 ',,"',. 14~ .. -----------'L:.:.::,-'SOiL'1'-'. 13,640:,210 B.P. " -',

SOILI ~", lJ,96~1S0 B.P. 15,270%,170 B.P. SlIalifitd Grhtb Illd SllIdo

..-,-,w.

i ---~~------~=-------~~--------~'o~--------~lUo~m~------~" - ,~no.. 400.. JOO.. . 0

Richard Beene Site (41BX83l)

San Antonio, Texas March 27-29, 1992

Page 2: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

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Lubbock Lake Landmark Quaternary Research Center Series 4 (Draft)

GUIDEBOOK 10th Annual Meeting

South-Central Friends of the Pleistocene

LATE CENOZOIC ALLUVIAL STRATIGRAPHY AND PREHISTORY OF THE INNER GULF COASTAL

PLAIN, SOUTH-CENTRAL TEXAS

San Antonio, Texas March 27-29, 1992

Leaders and Editors: Rolfe D. Mandel

Geography-Geology Department University of Nebraska-Omaha

and S. Christopher Caran Geology Department

University of Texas at Austin

Contributors: Barry W. Baker, Department of Anthropology, Texas A&M University

George W. Bomar, Texas Water Commission, Austin, Texas B. R. Brasher, USDA, Soil Conservation Service, Lincoln, Nebraska

Vaughn M. Bryant, Jr., Department of AnthrOpology, Texas A&M University 1. Philip Dering, Department of Anthropology, Texas A&M University Wayne J. Gabriel, USDA, Soil Conservation Service, Uvalde, Texas

Wulf Gose, Geology Department, University of Texas at Austin John S. Jacob, Soil and Crops Sciences, Texas A&M University

Lynn E. Loomis USDA, Soil Conservation Service, Uvalde, Texas Ernest L. Lundelius, Jr., Department of Geological Sciences, University of Texas at Austin

Raymond W. Neck, Houston Museum of Natural History Curt J. Sorenson, Department of Geography, University of Kansas

D. Gentry Steele, Department of Anthropology, Texas A&M University Dennis Trombatore, Department of Geological Sciences, University of Texas at Austin

Alston V. Thoms, Department of Anthropology, Texas A&M University Charles Woodruff, Jr., Consulting Geologist, Austin, Texas

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CONTENTS

CONTENTS .................................................•................................

ROAD LOG Rolfe D. Mandel and S. Christopher Caran ........................................... .

STOP DESCRIPTIONS Rolfe D. Mandel and S. Christopher Caran, with contributions by Alston Thoms, John Jacob, Curt Sorensen, and Wulf Gose ........................................ .

GENESIS OF THE QUIHI SOIL IN THE UVALDE GRAVEL OF SOUTH-CENTRAL TEXAS

4'nn E. Loomis, Wayne J. Gabriel, and B. R. Brasher .......................... ..

THE CLIMATE OF THE INNER GULF COASTAL PLAIN OF SOUTH-CENTRAL TEXAS

George W. Bomar ....................................................................... .

QUATERNARY FAUNAL ASSEMBLAGES FROM CENTRAL TEXAS Ernest L Lundelius, Jr .................................................................. .

A LATE PLEISTOCENE THROUGH LATE HOLOCENE FAUNAL ASSEMBLAGE FROM THE RICHARD BEENE SITE (4IBX831), BEXAR COUNTY, SOUTH-CENTRAL TEXAS: PRELIMINARY RESULTS

Barry W. Baker and D. Gentry Steele ............................................... ..

PLANT REMAINS FROM THE RICHARD BEENE SITE (4IBX831): IMPUCATIONS FOR HOLOCENE CLIMATIC CHANGE IN SOUTH-CENTRAL TEXAS

J. Philip Dering and Vaughn M. Bryant, Jr .......................................... .

lATE PLEISTOCENE AND HOLOCENE PNVIRONMENTS IN THE MEDINA VALLEY OF TEXAS AS REVEALED BY NONMARINE MOLLUSCS

Raymond W. Neck ...................................................................... .

LATE PLEISTOCENE AND EARLY HOLOCENE REGIONAL LAND USE PATTERNA: A PERSPECTIVE FROM THE PRELIMINARY RESULTS OF ARCHAEOLOGICAL STUDIES AT THE RICHARD BEENE SITE, 41BX831, LOWER MEDINA RIVER, SOUTH TEXAS

Alston V. Thoms ......................................................................... .

THE BALCONES ESCARPMENT--BORDERLAND OF THE AMERICAN WEST

C. M. Woodruff, Jr ...................................................................... .

NEOGENE AND QUATERNARY STRATIGRAPHY OF THE INNER GULF COASTAL PLAINS, SOUTH-CENTRAL TEXAS

S. Christopher Caran ................................................................... .

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PUBLICATIONS RELATED TO TIlE QUATERNARY OF SlXTEEN COUNTIES IN THE CENTRAL TEXASI BALCONES FAULT ZONE REGION: A BIBLIOGRAPHY

Dennis Tl'ombatore ...................................................................... .

ACKNOWLEDGMENTS ............•......................................................

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Road Log The field trip originates from San Antonio, Texas, each day (March 27- 29, 1992). See Figure 1.

DAY ONE (Friday, March 27, 1992)

Miles

0.0 Depart from the Howard Johnson Motel, Conference Headquarters, San Antonio, Texas.

0.2

Proceed out of parking lot and turn right (south) onto access road. Move into the far left lane.

Turn left (south) and cross under 1H-35.

0.4 Turn left on Randolph Boulevard

0.5 Turn left (north) onto Crestway. Crestway parallels 1H-35 as an access road.

l.4 Bear left and enter 1H-35 North, continuing north to San Marcos, Texas. The interstate highway parallels the Balcones Escarpment, the line of hills to the west of the highway. The surface of the Edwards Plateau is about 600 m above the Inner Coastal Plain along the escarpment in this area. Between San Antonio and New Braunfels, Texas, note the many large quarries recovering Lower Cretaceous Edwards limestone for concrete manufacture and crushed aggregate.

39.2 Exit 1H-35 North and get into the right lane of the access road.

39.4 Turn right (east) onto combined Texas Highway 21180.

40.5 Turn left (north) onto Texas Highway 21 (Old Bastrop Highway).

75.5 Turn right (east) onto Texas Highway 71 toward Bastrop,Texas.

79.4 Turn right (south) onto Farm Road 304. We are on the low, broad T-l terrace (Holocene) of the Colorado River at the intersection of Farm Road 304 and Highway 71. Farm Road 304 crosses three terrace scarps as we continue to Stop 1.

88.1 Turn left (east) onto gravel road leading into gravel pit.

88.2 Stop 1 - The Tiner Section.

This locality is on the scarp of a prominent northward-facing terrace of the Colorado River, lying approximately 1.5 mi to the northeast. Heavily iron-cemented sands and gravels overlie the Eocene Carrizo Formation, a thick nonmarine sandstone.

Tum around and travel back along the gravel road to Farm Road 304.

88.3 Turn right (north) onto Farm Road 304.

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Figure 1. Regional location map.

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95.6 Tum left (west) onto Bastrop County Road 82 and immediately tum right (north) onto grnvel road leading into grnvel pit.

95.8 Stop 2 - The Townsend Section.

The gravel pit at this locality occupies a terrace remnant only slightly higher than the surface we drove across when approaching the site. Iron-stained sands and gravels are exposed in the northern wall of the pit.

Tum around and travel back to Bastrop County Road 82.

96.0 Tum left and come to an immediate stop. Then tum left (north) onto Farm Road 304.

97.4 Tum right (east) onto Texas Highway 71 toward Bastrop,Texas.

99.3 Cross the Colorado River in the town of Bastrop, Texas.

100.1 Tum left (north) onto combined Texas Highway 21/95.

100.4 Tum right (east) onto Texas Highway 21.

101.2 Tum right (south) onto Bastrop State Park entrance loop.

101.3 Tum left (east) on Bastrop State Park Road 1A.

101.9 Take the right (south) fork of Bastrop State Park Road (Loop) lA at the Dining Hall. Continue on the park road as it loops counterclockwise toward Stop 3 (Lunch).

103.1 Tum left (west) into camping area and continue west to covered pavilion at the end of the road.

103.3 Stop 3 - Lunch.

Food will be served under the pavilion, but feel free to climb the hills and walk through the camp grounds. Please dispose of trash properly.

Tum around and head east to Bastrop State Park Road (Loop) 1A.

103.5 Tum right (south) onto Bastrop State Park Road (Loop) lAo

104.7 Tum left (west) onto entrance segment of Bastrop State Park Road 1A.

105.3 Tum left (south) onto Bastrop State Park entrance loop.

105.4 Tum left (east) onto Loop 150. The loop will tum to the south and merge with Texas Highway 71, but instead bear right as you approach the highway.

106.2 Cross Texas Highway 71 into the Tahitian Village development

106.3 Gate entrance to Tahitian Village. Continue south on Tahitian Drive.

108.5 We are on the modern floodplain (lowest surface) of the Colorado River at the intersection

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of Tahitian and Riverside Drives. Turn left (east) onto Riverside Drive and continue east as the road climbs Red Bluffs. The road curves left at the top of the bluff.

108.8 Turn left (west) into parking area for Stop 4.

108.8 Stop 4 - Red Bluffs Section.

109.1

110.3

110.3

110.4

111.5

112.7

112.7

117.4

120.1

120.2

121.9

122.2

124.4

124.6

Red Bluffs rise dramatically from the Colorado River to a high but deeply dissected terrace. Thick Pleistocene fluvial deposits with well developed paleosols overlie the Eocene Carrizo Formation.

Turn around in the parking area. Turn right (south) onto Riverside Drive.

Turn right (north) onto Tahitian Drive.

Turn right (east) onto Pahalawe Slreet and pull over on the right side of the road.

Stop 5-Tahitian Drive and Pahalawe Street Roadcuts.

Turn around at the bottom of the hill.

Turn right (north) on Tahitian Drive.

Turn right (east) on Texas Highway 71.

Pull over on right side of the highway.

Stop 6 • Highway 71 Outcrop.

A thick section of the Pliocene sandstone (Reklaw Formation?) is exposed on the north side of Texas Highway 71. There is an ironstone "caprock" at the top of the section.

Exit to Texas Highway 95/Loop 230.

Turn right (south) on Texas Highway 95/Loop 230.

Cross the Colorado River.

Loop 230 forks to the left. Continue south on Texas Highway 95 through Smithville, Texas.

Turn left (east) on Helkat Lane.

Turn right into driveway of John Harrell's home, and park the vehicles. Walk north 0.1 mile and tum left (west) through the gate leading to the Rehmet Volcanic Ash Locality (Stop 7).

124.7 Stop 7 • Rehmet Volcanic Ash Locality.

Turn right (south) on Easy Slreet as you pull out of driveway.

125.8 Turn left (east) on Baslrop County Road 316.

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126.9 Turn left (north) on Bastrop County Road 31S. The road jogs at several points. Stay on the paved surface.

12S.6 Turn left (north) onto Bastrop County Road 321.

129.1 Gravel piton right

129.5 Turn right (east) on gravel road leading into sand pit.

129.6 Stop 8 - Clark Sand Pit and Archaeological Site.

129.6 This concludes day I of the field trip. Exit the gate at the Clark Locality and turn right on Bastrop County Road 321. Travel 1.3 miles north to Loop 320.Turn right (north) on Loop 230 and travel 0.4 miles east to Texas Highway 71. Go under Texas Highway 71 and turn left (west) onto the access road. Enter Texas Highway 71 and travel west toward Bastrop. From Bastrop, retrace the route back to San Antonio. Turn left (south) on Texas Highway 21 to San Marcos.Turn right (west) on combined Texas Highway 211S0 to IH-3S. Go under IH-35 and turn left onto the access road. Enter IH-35 and travel south to San

Miles

0.0

0.2

O.S

S.9

9.5

IS.I

23.4

23.S

27.9

29.0

31.4

33.0

Antonio. Exit at Randolph Blvd. for Howard Johnson Motel.

DAY TWO (Saturday, March 28, 1992)

Depart from the Howard Johnson, Conference Headquarters, San Antonio, Texas. Proceed out of parking lot and turn right (south) on access road. Move into the center lane.

Cross intersection and proceed south onto the access ramp for IH-35 South.

Bear left onto the main ramp for 1H-3S South.

Bear right onto long ramp for 1-37 South (Corpus Christi exit).

Merge onto 1-37 South .

Exit right (west) onto Loop 410 West.

Exit right for Moursund Blvd.Continue west on access road.

Turn left (south) on Moursund Blvd. Moursund B1vd.becomes Pleasanton Road.

Cross the Medina River.

Turn right (west) on Neal Road.

Turn right (north) and stop at gate leading into the Applewhite Lake project area. Proceed north on private road.

Stop at the south end of the large trench for footing of the dam.

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33.0 Stop la • The Richard Beene Site (41BX831).

Stop Ib • Backhoe trench excavated into the Miller Terrace.

Stop lc • Backhoe trench excavated into the Leona Terrace.

Stop Id • Backhoe trench excavated into the Walsh Thrrace.

34.5 SlOP at gate. Exit the Applewhite Lake project area and proceed west on Neal Road.

35.8 Tum left (south) on Applewhite Road.

37.0 Tum right on Loop 1604.

37.2 Tum left (south) on Oak Island Drive.

37.3 . Tum left (east) onto dirt road leading into Oak Island Sand Pit (Stop 2).

38.1 Stop 2 • Oak Island· Sand Pit. Tum around and follow dirt road out of the sand pit

38.8 Tum right (north) on Oak Island drive.

38.9 Tum left (west) on Loop 1604.

41.1 Tum right (north) at exit to Texas Highway 16.

41.2 Tum left (west) on access road for Texas Highway 16.

41.4 Tum right (north) on Texas Highway 16.

43.3 Cross the Medina River.

44.2 . Tum left (west) on Watson Road. Pass the Alamo Dragway.

47.2 Stop at intersection with Somerset Road. Cross the intersection and proceed west

47.7 Tum left (south) into Hidden Valley Recreational Park. Proceed south on gravel road.

49.0 Stop 3 • Lunch in Hidden Valley Park.

Tum around and proceed north on park road.

49.3 Tum left (west) on dirt road adjacent to Hidden Valley Office and stop.

49.3 Stop 4 • Hidden Valley Section.

Tum around and proceed north on park road.

49.8 Tum left (west) into gravel pit and stop.

49.9 Stop 5 • Jlidden Valley Sand and Gravel Pit.

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Turn around and proceed north on park road.

50.5 Turn right (east) on Watson Road.

51.0 Turn right (south) on Somerset Road, then bear left onto Quesenberry Road (gravel road).

52.2 Turn left (east) on unnamed gravel road.

52.4 Tum right (south) at gate. Proceed south on private gravel road.

53.0 Stop 6

53.0 This concludes day 2 of the field trip. Exit the gate at the Stop 6 and tum left on gravel road. Turn right on Quesenberry Road and proceed to Somerset road. Tum right (north) on Somerset Road and proceed to Loop 410. Tum right (east) on Loop 410 and retrace the route back to Howard Johnson Motel. Take the 1lI-37 North exit, then exit at IH-35 North (Austin exit). Proceed north on 1lI-35. Exit at Starlight Terrace. Turn left at Turnaround and proceed under 1lI-35 North. Turn left on access road and proceed south to Howard Johnson Motel.

DAY THREE (Sunday, March 29, 1992)

Miles

0.0 Depart from the Howard Johnson, Conference 'Headquarters, San Antonio, Texas. Proceed out of parking lot and tum right (south) on access road. Stay in the right lane.

0.2' Cross intersection and bear right onto the access road for Loop 410 West.

1.5 Enter Loop 410 West.

20.1 Exit right (west) to US Highway 90 West (Del Rio). Stay on the access road.

20.8 Enter US Highway 90 West and proceed toward Castroville, Texas.

34.9 Cross the Medina River in the town of Castroville.

35.5 Begin to ascend a high scarp mantled with Uvalde Gravel.

36.6 Pull over at scenic overlook.

36.6 Stop 1 - Scenic Overlook of the Medina River Valley.

36.5 Turn left (south) onto Farm Road 1343. Immediately turn left (east) onto dirt road. The dirt road becomes a paved road. Proceed east.

36.8 Turn right (south) and stop at gate. Proceed south on private dirt road.

37.3 Stop at backhoe trench.

37.3 Stop 2 - Quihi Backhoe Trench and Gravel Pit.

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Stop Descriptions

Portions of the stop descriptions were prepared by Chris Caran, Rolfe Mandel, Alston Thoms, John Jacob, Curt Sorenson, and Wulf Gose

Stop 1. Pleistocene Alluvial Deposits Exposed in the Tiner Sand and Gravel Pit.

At this stop we will examine heavily iron-cemented Pleistocene fluvial deposits underlying a high terrace of the Colorado River. The surface of this terrace is -46 m (150 ft) above the low­flow stage of the Colorado, and corresponds to the Capitol Terrace in Austin and to the Red Bluffs Terrace in this reach of the valley (Figures 2 and 3; Table I; see also Caran, this volume). It is one of the highest surfaces in this reach, but lower than the highest surfaces immediately across the river (Stops 3 and 5). Gullies and small streams have dissected this terrace deeply, especially , I along the scarp separating it from the next lower fill surface. The Tiner Sand and Gravel Pit was excavated into this scarp (Figure 2), exposing a 6-m-thick section of alluvium along the west headwall. Our discussion will focus on this section. .

The lower 5 m of the Tiner section is largely composed of coarse to very coarse sand and gravel. These were the basal sediments of the Colorado River paleochannel lying just above the unconformity on Eocene Carrizo sandstone (Unit I), which is exposed in the floor of the pit -30 m (100 ft) east of the headwall. Terrace fIll directly overlying the Carrizo (Unit II) have a mixed mineralogy dominated by quartz, quartzite, chert, and feldspar clasts. The sands are leached of carbonates and exhibit strong, oxidized colors (2.5YR hue); yet primary sedimentary structures, including tabular bedding and trough cross-bedding, are well preserved throughout the unit.

Unit II is capped by dense ironstone (ferricrete) near the top of the section (Figure 4). The ironstone is -1 to 1.5 m thick and is continuous across much of the exposure, but fractured and disrupted in places. Colluvium and/or slope-wash, including Iithoclastsof ironstone, accumulated in these local depressions. A soil (3Bt4) developed in the colluvium and underlying fluvial deposits where the ferricrete had been breached. The ferricrete is now "within" the upper part of this soil, but necessarily pre-dates pedogenesis, since Iithoclasts of ferricrete form part of the soil's parent material. This soil was subsequently burled by Unit III and became a paleosol. The paleosol matrix is red (lOR 4/6, dry), strongly acid, moderately low in bases, and has Btsm-Btsg­BCts horizonation (Table 2). Micromorphological analyses detected prominent clay ftIms and iron coatings in the paleo-solum (Figure 5). These features are also evident in non-cemented portions of the Btsb horizon. .

The paleosol is mantled by 65 to 85 cm of coarse-grained fluvial deposits (Unit III). Chemical and grain-size data (Tables 3 and4) reveal dramatic differences between the soils developed in Units II and III. For example, soil pH increases from 4.4 in the paleosol in Unit II to 7.1 in overlying Unit III. The clay-free sand/silt ratio decreases from 7.2 to 2.5, base saturation increases from 59 to 98 percent, and organic carbon increases from 0.26 to 0.62 percent. A well­expressed surface soil with A-E-Bts horiwnation is developed at the top of Unit III. The soil incorporates cobble- and boulder-size Iithoclasts of locally derived ironstone. The Bts horizon, in aggregate, is 55 cm thick, dark red (2.5YR 3/6, dry) to red (lOR 4/6, dry) in color, and clay in texture. Soil structure in the Bts horizon is subangular blocky with distinct ferriargillans on clasts and ped faces. .

At first glance the Tiner section has soil characteristics that are oxic-like, notably a ferricrete (pedogenic laterite) or iron-cemented B horizon. Soils with similar characteristics have been reported from localities throughout the world (e.g., Thorp and Reed 1949; Dury and Knox 1971; Goudie 1973; Nahon et aI. 1980). They are but one category in a class of cemented soil­geomorphic features known as duricrusts (1\vidale 1976; Retallack 1990). Although opinions vary widely regarding the origin of these features, there is general agreement that most are pedogenically derived and further, that crust hardening is enhanced at the edges of escarpments where drainage

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Figure 2. Location map, Stop I, showing line of section A-A'.

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StI E1w. (A)

m It 140

450

"I1 OQ' c @ ~ 400

~ 1211

tr '< - (")

0 a ~

~ a. 0 350 ::s ;.. , ~ 100

lIIfI

NE (A')

TIn... gravel pit (Stop ,. Colorado River valley

Terrace ttReJlef m

155...--.47

oontact: Pier.tacen. lran-.. mentad fluvial depoolto overfyIng Eocen. Conizo Fonnatlon

uMamed aurfac.

road unnamed tributary of Colorado

Elevation of hlghut reported flood of Colorado _ at Baatrop. July 7 or B. 1869 (Buckner and ath.... 1987. p. 155): lOll' 367.7 ft (112.1 m).

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eroded ) 90 %1 """nant of HIli. :!!-=~!...t _._._. ._._ D rnl

r gen..... elevation 65 211 ______ ~ of Hili. Pralrl. Crofto &on lie 1

Pralrl. . Ii: iil -t-'

Topographic ba •• : 8a.trop. Texaa 7.5-mln topographic quadran~l. map (Geological Survey. 1982)

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Vertical exaggeration: 68.8X

David Bottom

road

1.land (.ubaerfol bar)

~

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121.

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Table 1. Relief of the Colorado River terraces in the l~~~r_fg~~~~l_El~l~ __________________________________________ _

Terracel Relief above Colorado River (low-flow stage): as terrace reported previously (1-6); as described here (7-9) q~~~~ii~ ___ l _____ s _____ ~ _____ ~ _____ ~ _____ ~ _____ Z _____ § _____ ~ __

Uvalde*

Asylum

Capitol

230- 250 ~200- 213- 200+ 230+ 330 279 280

195- 160- 195- 197- 180- 197-215 190 210 213 197 213

105- 100 130- 131- 100- 131-130 160 158 130 157

Montop- NR NR 75- 75- NR 75-olis 90 92 82

NR

180-210

100-130 NR

Sixth 80 75 60 59- 65- 59- 60-Street 66 80 66 80

First 60? 24- 30- 33- 33- 33- 30-Street 45 40 50 50 50 50

River- NR? 16- NR 20- 20- 20- 18-view 28 33 33 33 30

Sand ~10? NR NR 7- 7- 7- 8-Beach 16 16 16 18

NR

190-230

100-155 NR

65-90

40-60

~25-

40 i25

NR

195-240

105-160 NR

65-90

40-65

~30-

40

River 422 NR ~420 NR NR NR 422** 290- 270-__ ~l~Y~ ______________________________________________ ~sQ ___ s§~

*The Uvalde Formation as defined by Hill (1895) is not a Colorado River terrace, although many investigators have described and lor treated it as such. Furthermore, it is doubtful that the Uvalde exists as a discrete stratigraphic entity north of the San Antonio River basin (see text).

**The elevation cited is that given by Hill and Vaughan (1897, p. 244) for the low-flow river stage in central Austin. Longhorn Dam impounded the river in 1960, creating Town Lake, with a pool elevation of 428 ft. Elevation of the river in Austin below Longhorn Dam is ~400 ft.

NR = Not reported or not recognized

1 :

2: 3: 4: 5: 6:

Hill and Vaughan (1897, p. 244, 248>; ~~~ o!!.!.§'~ Hill (1901, p. 352) and Hill and Vaughan (1902). Deussen (1924, p. 115-116) Weber (1968) Baker and Penteado-Orellana (1977, Table 1) Looney and Baker (1977, Table 3) Blum (1991, Table 6.5)

7-9: Relief as shown on the following topographic maps: 7--Austin East (Geological Survey, 1973a) and Montopolis (Geological Survey, 1973b); 8--Bastrop (Geological Survey, 1982) and Lake Bastrop (Geological Survey, 1982); 9--Smithville (Geological Survey, 1982) and Togo ( Geo log i cal Sur vey, 1981).

Page 17: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Figure 4. View of Tiner Section showing massive ironstone at top of exposure.

12

Page 18: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

--

o..scription of the Tiner Section.

o..pth Color Struc- Tex- Consis- BoUD-Horizon (cm~MQist DrY lUre lure te=_ dar\' . Soecial Feal!!res

A (}'15 7.5YR3/3 7.5YR5/3 IfGR LCoS vfr c,s Common very fine and few fme and medium roots; common rounded and subangular chert, quartz, and quartzite pebbles; few ironstone cobbles and boulders.

E 15-30 2.5YR3/6 5YR5/4 IfSBK-ImGR LCoS vf a,s Common very fine and few fine and medium roots; common rounded and subangular chert, quartz, and quartzite pebbles; few ironstone cobbles and boulders.

Btsl 3(}'40 2.5YR3/6 2.5YR3/6 2mSBK-2fSBK GSCL fr c,s Few fine and very fine roots; slightly sticky when moist; few ferriargillans on clasts and vertical ped faces.

Bts2 4(}'56 IOR4/6 IOR4/6 3mSBK-ImSBK C fr g.i Few fme and very fme roots; few rounded and subrouoded quartz, chert, and feldspar pebbles; slightly sticky when moist; common ferriargillans on clasts and vertical ped faces.

Bts3 56-85 IOR4/6 IOR4/6 3mSBK-ImSBK C fr a.i Discontinuous massive ironstone; few fme roots; few (10%) IOYR5/8 stains on ped surfaces; common ferriargillans on clasts and vertical ped surfaces; 3(}' 50% of matrix consists of feldspar clasts.

2Btsb 85-116 IOR4/6 IOR4/6 3mSBK-ImSBK GSCL fr a,w Discontinuous massive ironstone; few fine roots; few (10%) -, IOYR5/8 stains on ped surfaces; common ferriargillans on clasts and vertical ped surfaces; 60% of matrix is coarse (2: pebbles); common ironstone lithoclasts.

3Btsgb 116-137 50% IOYR4/6 2m+fABK-vfABK CL h a,w Reduction zones (2.5Y612) on ped faces and along root channels. 50% 2.5Y612

4BCtsb 137-190 2.5YR4/8 2.5YR4/8 ImSBK GSCL vh g,s Most of matrix consists of stratified gravel; indurated; common ferriargillans on clasts; common ferromanganese stains.

5C 190-560 2.5YR4/8 2.5YR4/8 M CoSL vh Stratified sand and gravel; indurated.

Abbreviations: Structure: I=weak, 2=moderate, 3=strong, f=fme, m=medium, c=coarse, P=prismatic, SBK=subangular blocky, ABK=anguiar blocky, GR=granular, M=massive Texture: S=sand, Si=sil~ C=clay, L=loam,V=very, F=fine, Co=coarse, G=gravelly Consistence: fi=frm, fr=friable, h=hard, v=very Boundaries: c=clear, g=gradual, a=abrup~ s=smoodl, w=wavy, i=irregular

Symbols: (+) and; (-) parting to

Page 19: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

' .

. /

b

,. .~"';"_ ..... o.---J.I M 4i'·_A

Figure 5. Photomicrographs of thin sections, Tyner section. a). Bt2 horizon, PPL. Clay tilm overlying dense Fe-crystic fabric. b). Tyner section, 3Bt4 horizon, XPL. Iron and clay coats in sandy matrix. Note weathered fedlspar particle in lower right corner. All bar lengths 100 micrometers.

14

I, I

)

)

Page 20: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

-~

Table 3.Chemical properties of soils in the Tiner Section.

Exchangeable Ba~e~ Base Organic Horizon Del!th C!I Mg Na K CEC S!ltllration CEC/Qay Carbon 11H

----------------------rnflq/l(H)g-------------------- --%-- ---%--

A 0-15 13.2 0.7 0.2 0.3 13.1 1(H) 2.60 1.63 7.6 E 15-30 6.2 0.4 0.1 0.2 5.7 1(H) 1.20 0.38 8.1

Btsl 30-40 11.0 1.4 0.3 0.5 15.2 87 0.60 0.62 7.6 Bts2 40-56 18.2 4.5 0.2 1.2 24.6 98 0.41 0.85 7.4

Bts3 56-85 17.5 6.3 0.2 1.3 25.8 98 0.49 0.82 7.1 2Btsb 85-116 4.8 4.6 0.3 0.7 17.7 ·59 0.56 0.62 4.4

3Btsgb 116-137 8.6 4.6 0.3 0.7 17.7 59 0.56 0.26 4.3 4BCtsb 137-190 4.5 4.6 0.5 0.3 22.1 45 0.81 0.21 4.4

5C 190-240 5.2 4.5 0.7 0.3 15.7 68 0.63 0.14 4.8 6C 320-330 2.2 2.4 0.8 0.1 6.5 84 0.47 0.16 4.4

7C 450-460 5.9 4.2 0.5 0.5 16.1 69 5.1

8C 550-560 2.7 1.7 0.4 0.2 10.6 47 0.53 0.20 5.2

Page 21: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Tabl~ 4. Particl~-size distributions: Tiner Sand and Gravel Pit. ~ilD!!* :!il! ~Ii)~ V. F. Sandi Clay-me

HQ[g;QO IXptb V!:; !:; M F YE Total Finc IQta\ Fine Total I~lnn:~A EiD~ :lIm! SmdlSill - -c:m-- - - - - - - - - - - - - - - - - - - - - - - - - - wI. % - - - - - - - - - - - - - - - - - - - - - - - - -

A 0-15 14.7 10.8 16.4 18.2 14.8 74.9 12.8 20.2 1.6 4.9 LCoS 0.8 3.7

E 15-30 13.5 12.8 16.4 20.0 15.8 78.5 9.3 27.0 1.5 4.5 LCoS 0.8 2.9 Btsl 30-40 9.2 10.6 12.0 13.9 12.3 58.0 12.7 16.6 15.8 25.4 SCL 0.9 3.5 Bts2 40-56 4.0 4.7 5.8 6.1 6.8 27.4 7.6 12.9 47.3 59.7 C l.l 2.1 Bts3 56-85 11.2 6.7 4.8 5.1 6.3 34.1 4.8 13.7 39.2 52.2 C 1.2 2.5 2Btsb 85-.116 28.4 10.7 7.6 8.4 5.1 60.2 4.4 8.4 22.4 31.4 SCL 0.6 7.2 3Btsgb 116-137 5.5 4.8 6.9 7.8 18.3 43.3 6.6 17.5 32.5 39.2 CL 2.3 2.5 4BCtsb 137-190 11.3 21.8 25.5 6.7 3.4 68.7 2.7 4.2 19.8 27.1 SCL 1.5 16.4 5C 190-240 22.1 20.9 12.8 6.5 3.8 66.1 4.7 9.2 16.4 24.7 SCL 0.6 7.2 6C 320-330 23.2 36.6 16.0 5.1 1.7 82.6 1.3 3.5 8.9 13.9 CoSL 0.3 23.6 7C 550-560 32.9 23.3 14.0 3.7 1.6 75.5 2.6 4.7 13.6 19.8 CoSL 0.4 16.1

*Particle-size limits (mm): Sand: VC = 2.0-1.0, C = 1.0-0.5, M = 0.5-0.25, F = 0.25-0.10, VF = 0.10-0.05 Silt: Total = 0.05-0.002, Fine = 0.02-0.002 Clay: Total = < 0.002, Fine = <0.0002

-'I'exture classeS: S=sand, Si=silt, C=clay, L=loam, V=very, F=tine, Co=coarse

Page 22: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

and aeration are strongest (Pugh 1966; Daniels and Gamble 1967). The age of the ferricrete in the Tiner section is unknown, but elsewhere ferricretes are mid to late Tertiary relicts, although some may be as young as Pleistocene (Twidale 1976). Correlation of the Colorado River terraces indicates that the ferricrete at this locality is almost certainly no older than Middle Pleistocene (see Caran, this volume).

Several types of evidence argue against extreme antiquity (i.e., pre-Pleistocene age) of at least the uppermost soil and Unit III. Most obvious is the presence of feldspar clasts in the Btsm horizon. One would normally expect conversion of feldspars to secondary minerals in such a seemingly deeply weathered profile. In addition, the CEC/clay ratios (> 0.40) suggest that the clay-mineral suite is dominated by smectite instead of kaolinite, a more residual clay. The problem in interpretation posed by the opposing characteristics of ferricrete morphology in the presence of feldspars and smectite is anomalous unless the terrace fill was truncated prior to development of the surface soil, as suggested here. Other possible explanations await further research.

Stop 2. Pleistocene Alluvial Deposits Exposed in the Townsend Sand and Gravel Pit.

At this stop we will briefly examine the lithology of alluvium composing valley fill beneath a low Pleistocene terrace of the Colorado River. A 5 m-thick section of fill (mostly coarse-grained) is exposed in an abandoned sand and gravel pit about 4 km southwest of Bastrop, Texas (Figure 6). The surface of the terrace is more than 20 m (66 ft) above the modem low-flow channel of the Colorado, and 25 m (82 ft.) below the highest surface on the cross-valley profile through this site (Figure 7). The terrace at Stop 2 is correlative with the Sixth Street Terrace in Austin and to the Antioch Terrace of the Bastrop area (Table I). Unlike the high terrace observed at Stop I, this low terrace is fairly flat and undissected, although only an isolated remnant is preserved at this site. An Alfisol, nominally representing the Demona senes, caps this remnant. The bulk of the terrace fill at Stop 2 consists of stratified sand and gravel. Note the wide variety of clast types, many of which are reworked exotics, including quartzite, vein quartz, dark (Pennsylvanian?) chert and other cherts (mostly Lower Cretaceous), Tertiary silicified wood, granite, and rare indurated Lower Cretaceous limestone particles and reworked fossils. The source of much of the alluvium is older Colorado terrace deposits plus some newer material derived from bedrock exposed in the Central Mineral Region (Llano Uplift), Edwards Plateau, and Inner Gulf Coastal Plain. The older terrace fills that contributed alluvium to this terrace were composed of material derived from primary sources and former fluvial systems for which there is a sedimentological record, but no remaining geomorphic record.

Stop 3. Lunch in Bastrop State Park. Much of Bastrop State Park is on the highest geomorphic surfaces in the Coastal Plains portion

of the Colorado River Valley. Hill tops within the severely dissected landscape at this stop are -67 m (225 ft) above the modem river channel, and 23 m (80 ft)) above the high terrace (Capitol) surface at Stop 1 (Figures 8 and 9 and Table 1). This is the highest recognized fill terrace of the ancestral Colorado River in the Coastal Plains, equivalent to the Asylum Terrace at Austin. In the Bastrop area, the terrace corresponding to the Asylum is here designated the State Park Terrace. The park includes even higher surfaces, however. Approximately 1.6 km (I mil northeast of Stop 3, elevations increase to 187 m (612 ft), more than 95 m (312 ft) above the river. Ironstone caps Eocene sandstone on these high surfaces. Ironstone capped ridge tops can be seen throughout the park, including the campground at Stop 3, where iron-cemented fluvial terrace gravels and gravel lags overlie the Carrizo sandstone. Hill sideslopes and footslopes are mantled with colluvial sediment derived from these caps.

Soils in Bastrop State Park are classified as Paleustalfs (Alfisols) in the Soil Survey of Bastrop County. Texas. Soils on the very highest surfaces in the park are, however,

17

Page 23: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

: I : I

.. ------;--1 I I

I )

Figure 6. Location map, Stop 2, showing line of section 8-B'.

18

I I I

I I I • ! ~.

I I

t: "", \ ,

\

)

Page 24: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

!l "" '" iil ;--I

e: is"

'< ~ (")

co (3 '" '" '" ~ ~ o· :>

Cll , Cll

NW E1cv. (B)

m It 1411

4IiO

400 1211

J50

100

]OQ

'--

Sf (B') Torrace

fl R .. lef m 155~47

Colorado River volley

Elevation 01 hlghut reported 1l00d 01 Colorado Rlvv at 8o.tn>p. July 7 or !I. 1869 (Buckner and oth.,... 1987. p. 1 SS): 317.7 It (112.1 m).

u pt a_-d 01 lioupt Bend 1 orodod margin

nOU ..,.,. aurface Colorado RlYllr· aurface (lioupt Bend) - • - • t . - . - . . - obandonod

i 100 JII

9OD'D ~l Iii.,

65 20 6Or-r1l

Quaternary tcm:u:. fliia ovenylng Eocene WIlcox Group

-- I fIood-ploln chutr rldgo and Colorodo .. oJe RIval'

Quotomory terrace "". (liou t oyortying Eoceno Wilcox Croup l Bend~ 411

~j 1i:U;

12 L •

Topographic base: Baatrop. TO:03 7.S-mln topographic quadran91e map (Geological Survey. 1982).

o 1 ml

o km Vertical exaggeration: SS.6X

( " I water leval (low floW) \ ! II ? •

?

o

.H a I>:

o

..,.c <:0 00

"dl

Page 25: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Figure 8. Location map, Stops 3-6, showing lines of section C-C' and D-D'.

20

I I

Page 26: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

"I1 ciQ' c: Cil ~

~ 1> '<

I\) (") ~ ...

0

'" '" '" ~ ::t. 0 ::> n , n

~

S Nisw N~SE (Cl L-- lin. 01 •• ctlon chong •• direction ____ J

NWt N~W E (C')

Elcw. ~ m ft overlap with

201)' _ _ _ an. of .. etlan 0-0'

1110

1110

140

120

100

Colorado River valley

Tahitian Village aubdlvl.lon

Dluected landscape Colorado River (Incised by unnamed

trlbulori.. 01 Red Cappora. Creek) Bluff. (Stop 4)

'Appraxlmate conloct: Plelotocono lIuvlal dopoolla overiylng Eocen. Carrtzo Fm

JCG-l\ I water level ? (low Ilow)

lin. of aectlon chang.. direction

k Baotrop State Pari< (part) > Pork Rd. lC

gravel pIt

ThIn nolle! fluvial dopo.11a or lag gravel overlying Eocene Canrtzo Fm. Qu.t NE 01 Slop 5)

J HIghway 71 gravel 2

---------" Terrae. ReII.1

]

ft ~ Appraxlmcte E

pIt (Stop 3): PleIstocene fluvial dopo.11a overlying Eocene Carrizo Fm.

contact: Eocene ~ Reklaw FI.t. ~ (locally Iron cemented) I 511 overlying Eoceno Carrizo Fm.

TopographIc ba .. : Bastrop, Texa. 7.S-mln topographIc quadrangle map (Geologlcol Survey, 1982).

o d

I o km Vertical exaggeration: -40X

47

'0 '[ a

" 30

Il)) IS!)

;2f5 ~ii

J!,i o

Page 27: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

morphologically similar to the Rek and Tremona series, two Aquic Haplustults (U1tisols) formed on gravel<apped ridge tops (Willis Fonnation?) in adjacent Fayette County to the east. Both series have thick sola and strong red hues (2.5YR), but the Tremona is more depleted of bases. These soils are rich in kaolinite, and there is usually ironstone within the Bt horizon. We are in the process of analyzing the soils on the highest surfaces in Bastrop State Park to detennine if they are, in fact, ancient U1tisols.

Among the principal attractions of Bastrop State Park are the "lost" pine trees. Loblolly Pine (~ ~ is common here, but the species reaches its western limit in Bastrop County and Fayette County immediately to the east (Correll and Johnston, 1970: 72). Loblolly Pine is a dominant component of the forests of East Texas and the southeastern U.S. Wood from these pines was used to construct many of the buildings in the park. During the 1920's and '30' s, the Citizens Conservation Corps (Ccq made numerous improvements in the park grounds using pine and other native materials, including ironstone which was quarried here and used as a facing stone for buildings and walls.

Stop 4. Pleistocene Alluvial Deposits Exposed in the Red Bluffs Section. At this stop we will examine several thick sections of Pleistocene fluvial deposits and Eocene

sandstone beneath a high terrace of the Colorado River. These sections are exposed in roadcuts along the "Red Bluffs" of the Colorado River immediately south of Bastrop State Park (Figure 8). The surface of the terrace is -38 m (12S ft) above the modern low-flow channel of the Colorado, and -30 m (100 ft) below the highest terrace surface in the valley landscape (Figure 10 and Table 1). The terrace at Red BlUffs is correlative with the Capitol Terrace at Austin. The equivalent terrace throughout the Bastrop area is here designated the Red Bluffs Terrace.

The lower -6 m (20 ft) of the terrace fill (Unit II) consist of cross-stratified sand and gravel rich in chert, quartz, and quartzite, and trace amounts of granite/feldspar and other lithologies. The alluvium is leached and displays moderately oxidized colors (7.SYR hue). Fluvial gravels at the bottom of Unit II unconformably overlie Eocene Carrizo sandstone (Unit I), which are well exposed in the lower part of the section. The boundary between the sandstone and terrace fill is highly irregular and marked by a distinct iron-cemented gravel ledge (Figure 11).

A moderately thick paleosol is developed in coarse-loamy alluvium at the top of Unit II. This paleosol has been truncated, with only the Bt horizon remaining (Tables Sand 6). The SBtl b2 horizon is a dark red (lOR 3/6, moist) clay loam with a laterally variable percentage (maximum 80%) of light brownish gray (2.SY 612, dry) reduction zones along old and modern root paths. Thickness of the Btlb2 horizon varies between about 20 and 200 cm across the section, and the lower boundary of the horizon is gradual but extremely irregular, plunging downward into very narrow troughs at some places (Figure 12). The shape of these troughs, combined with the reticulate mottling pattern, iron enrichment, and clayey texture of the SBtlb2 horizon, suggest that the surface of the paleosol was greatly modified by tree roots prior to truncation and burial. As the root boll developed, the paleosol was bioturbated, destroying much of the original structure. I Whenever roots died and decayed they left conduits for enhanced illuviation of clay. The local reducing environment created by decaying organic matter caused accumulation of relatively insoluble ferrous iron scavenged from the clay minerals and intiltrating soil water. The surface on I wIIIh)iC~ theh.tree

h s w~lr~growedingCwhas eVl,:nt~!ly ~Olureddinh.partrfand bfruriedflbY ~a1uvdial d~sits (dUn hit .

, m w IC a SOl ,onn. anne mClslon ISO ate t IS su ace om UVI eposltJon an t e modern landscape began td take form. Gullying created an irregular topography on which slope wash and alluvium accumulated, creating a gravel lag (Unit IV). The modem weak soil is developed in Unit IV,

Destruction of the paleosol capping Unit II was partly curtailed by deposition of Unit III. Yet modification of this paleosol is occurring even today as modem roots seek moisture that is retained in the clay-rich SBtlb2 horizon. The roots move horizontally along the underside of an iron­cemented gravel at the base of Unit 3 until they reach the moist and relatively unconsolidated clayey

22

Page 28: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

N Co)

"Il QQ' c: @

9

~ " '<

~ '" a o· ::I

o q

Eloy. m ft

180

5110

140

~

400 120

~

1110

3110

NlSE S (D)

overtop ~'-lln. of Metlan nne of section chang.. direction

C-C'

Colorado River valley

Approximate Contact: Pleistocene fluvial ..apo.1ta overlying Eocene Carrizo

Rod Bluff.

(stop 4) N.

Hili. Prairie _. - .-f--.... (margin)

pvt. rd. Colorado

Rlvor

Quaternary terrace flll::s over­lying Eocene Carrizo Fonnatlon

Approximate contaI:C PlaJltocene fluvial dopo.1to overlying EGaln. Carrizo Formation

unnomed trfbutary 01 Cappo... Crt<.

Elevotlon of highest reported flood of Colorado RIver at Bo.trap. July 7 or 8. 1869 (Buckner and othors. 1987. p. 155): 367.7 It (112.1 m).

water level 1 (low flow)

'--

Baotrop state +:::v-+ NW Pork (ontrance) /toy. 21 (0') Terrace

Tahitian WI"lIe aubdMoion

.treet

N Rd. Pork \ ft Roll., m 150 '- Rei. '" 2JO...--. 70

otreot

Eocene carrizo Formation with local ven..,. of P1.18tocene fluvial depo.1to and/or lag gravel.

TopographIc baa.: Bastrop. Texas 7.S-mln topographic quadrangle map (Goologlcal Survey. 1982)

o ~

I o krn Vertical exaggeration: S8.eX

E

1 11O~5I

15:1 47

'0 :a o tJ

l00~30

IOD27u

65 20 60

40

2S

o

18

~] 1i:.,

12 L • Go!! ~>

a'"

o

.. '" e U 00 .,~

Page 29: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Figure II. View of iron-cemented gravel ledge at the base of Unit 11, Red Bluffs Section.

24

)

I

Page 30: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 5. Description of the upper 3 m of the easl-facing roadcul al the Red Bluffs Locality (SlOp 4).

Depth Color SIruC- Tex- Consis- BoUR-Horizon (cm) Moisl Orv IlIrjL I!!re lence ~F~es

Ap 0-20 IOYR313 IOYR413 ImSBK GLFS Ii" c.s Common fme and medium rools. C 20-60 7.5YR414 7.5YR514 M GLCoS Ii" a.i Gravelly colluvium; many chert clasts; few fine rools. 2BIs Ibl 60-94 2.5YR316 2.5YR416 2mSBK vGSCL Ii" a,w Common rounded. subrounded. and angular cobbles and pebbles;

common distincl ferriargillans on clasls and perl faces. 2Bs12bl 94-118 2.5YR316 2.5YR416 2cSBK GSCL Ii" a,w Irregular zones of Iex!Ure. 3Bls3bl 118-157 60% IOR316 2m+cABK GSCL Ii" a,w Gravel beds through the horizon and bounding if; red zones are

20% 5YR416 slightly brittle (plinthitic); reduced zones are clayey and less 20% 2.5Y416 brillie.

4BCsbi 157-178 2.5YR516 IfSBK 10 M GCoSL Ii" a,w Common horizon!al beds of cherly graveL 5Bllb2 178-193 80% 2.5Y6f1 IfSBK CL Ii" g •• Very sticky when moisl; distinct reticulale 2.5Y612 mottling;

20%IOR316 common medium roots. 5BI2b2 193-248 7.5YR416 7.5YR516 2mP-3mABK FSL vh g.s Common patchy 7.5YR3f1 clay films on vertical perl faces;

common (25-30%) 2.5Y6f1 reduction zones along perl faces; very hard when dry.

5 BI3b2 248-300 7.5YR416 7.5YR516 IcP-lmABK SCL vh Few patchy 7.5YR3f1 clay films on vertical perl faces; common (15-20%) 25Y6f1 reduction zones along perl faces;

Abbreviations: Slructure: I=weak, 2=moderale. 3=strong. f=fme. m=medium, c=coarse. P=prismatic. SBK=subangular hlocky. ABK=angular blocky. GR=granular. M=massive Texl!!re: S=sand. Si=sil~ C=clay. L=loam, V =very. F=fine. Co=coarse. G=gravelly Consislencdi=tirm. fr=friable. h=hard, v=very Boundaries: c=cl ..... g=gradual. a=abrup~ s=smooth. w=wavy. i=irregular

Symbols: (+) and; (-) parting 10

Page 31: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 6. Particle-size distributions: Red Bluffs Locality 5i!1ld* V. F. Sandi Clay free

H2dZQJJ DeI1!1i V~ ~ M E !it: Total Sill Clav >2mm TextJm: Ein, Si!Il!1 SlIIldlSill - -cm- - - - - - - - - - - - - - - - - - - - - owl % - - - - - - - - - - - - - - - - - - - - - - - ------wl%-----

Ap 0-20 2.9 7.9 18.4 34.0 15.7 78.9 15.4 5.7 21.0 GLFS C 20-60 19.7 IS.2 18.6 24.7 8.S 86.7 8.9 4.4 69.0 exGLCoS 2Btslbl 60-94 IS.7 19.4 19.8 IS.9 2.3 73.1 2.4 24.5 40.0 vGSCL 2Bts2bl 94-118 16.9 28.7 23.0 10.9 1.4 80.9 0.8 18.3 32.0 GSCL 3Bts3bl 1I8-IS7 9.8 22.S 24.7 13.8 1.7 72.5 1.1 26.4 30.0 GSCL 4BCsbl IS7-178 13.7 20.3 23.8 21.2 1.8 80.8 0.5 18.7 39.0 vGCoSL SBtlb2 \78-193 0.8 I.S 7.9 2S.7 9.8 45.7 18.9 3S.4 1.0 CL SBt2b2 193-248 7.7 8.7 12.2 2S.3 12.1 66.0 IS.9 18.1 0.0 FSL SBt3b2 248-300 4.3 6.9 IS.O 23.3 10.3 S9.8 17.2 23.0 11.0 SCL

·Particl"..size limits (mm): Sand: VC = 2.0-1.0, C = 1.0-0.5, M = 0.5-0.25, F = 0.25-0.10, VF = 0.10-0.05 Silt: Total = 0.05-0.002, Fine = 0.02-0.002 Clay: Total = < 0.002, Fine = <0.0002

"Texture classes: S=sand, Si=sil~ C=clay, L=loam,V=very, F=fine, Co=coarse, G=gravelly, ex=extremely, v=very

0.4 4.3 0.3 0.9 0.1 3.1 0.1 11.0 0.1 6.5 0.1 16.5 0.3 2.4 0.4 4.2 0.4 3.S

Page 32: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Figure 12. View of irregular surface of paleosol developed on Unit II, Red Bluffs Section.

27

Page 33: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

zones, where they extend radially. The 5Bt2b2 and 5Bt3b2 horizons have a combined thickness of about 1.4 m, and are strong

brown (7.5YR 516, dry) in color and fine sandy loam to sandy clay loam in texture. Soil structure is dominantly prismatic parting to angular blocky with patchy, dark brown (7.5YR 312, dry) clay films on vertical ped faces. The paleosol matrix is leached, and there are common (15-30%) light brownish gray (2.5Y 612, dry) reduction zones along root channels and ped faces.

As noted above, the lowest paleosol is buried beneath Unit III, a 1.0-1.5 m thick package of stratified sands and gravels. Unit III alluvium has a mixed mineralogy similar to that of Unit II, and is completely leached of carbonates. A well expressed paleosol is developed at the top and down through Unit III. This paleosol also has been truncated, with only the Bts horizon remaining (Table 5). The fine-grained soil matrix is red (2.5YR 4/6, dry) to dark red (lOR 3/6, moist) in color and sandy clay loam in texture. Soil structure in the 2Btslbl and 2Bts2bl horizons is medium subangular blocky with distinct ferriargillans on clasts and vertical ped faces. Red portions of the 2Bts3b 1 horizon are slightly brittle (plinthite?), and there are common (20%) light brownish gray (2.5Y 612, dry) clay-rich reduction zones along root channels.

The eroded surface of the upper paleosol is mantled by a 50-70 cm thick unit (Unit IV) of gravelly colluvium. A weakly expressed surface soil with A-C horizonation is developed at the top of Unit IV. The colluvium is dominated by chert cobbles (75-80%), and the < 2mm-fraction (5-10%) is loamy sand. Nearly all of the silt and clay have been winnowed out by sheetwash, leaving behind a very loose matrix of gravel that armors the underlying paleosol. This "lag gravel" is ubiquitous on the terrace at Red Bluffs, and will be observed at other localities high in the valley landscape.

The soil-stratigraphic record at Red Bluffs indicates that accumulation of alluvium on a former Pleistocene flood plain (now a high terrace) was interrupted by at least two major episodes of stability and soil formation. The lowermost buried paleosol was eroded down to and perhaps within its B horizon before being covered by alluvium. The uppermost buried soil also was severely eroded, but is mantled with colluvium. We suspect that repeated cycles of erosion and deposition may be the rule, rather than the exception, on most terrace surfaces.

All of the soils that developed in primary alluvium at Red Bluffs are moderately to highly oxidized with thick sola The uppermost buried soil is a PaleustaIf with strong red hues and a Bts horizon. The 2.5YR colors of the paleo-solum may be partially attributed to the later stages of the soil's development, after entrenchment inverted this landscape and promoted better drainage. However, a stronger weathering environment in combination with landscape inversion provide a better explanation for the magnitude of rubification and Bts-horizon development observed in alluvium at Red Bluffs.

Stop S. Tahitian Drive and Pahalawe Street Roadcuts. At this stop we will examine several sections that show colluvial lag gravels draped over red,

truncated paleosols developed in Pleistocene channel sands and gravels and/or Eocene Carrizo sandstone high in the valley landscape. The sections are exposed in roadcuts along Tahitian Drive and Pahalawe Street -1.6 km (l mil northwest of the Red Bluffs locality (Figure 8). The terrace surface at Stop 5 is 61 m (200 ft) above the modem channel of the Colorado River, -24 m (80 ft.) above the terrace surface at Red Bluffs, and is one of the highest surfaces in the valley (Figure 10 and Table I). The terrace at Stop 5 is correlative with the Asylum Terrace at Austin and with the Bastrop State Park Terrace (near Stop 3) of the Bastrop area.

The northern wall of the roadcut along Pahalawe Drive -40 m (130 ft) east of Tahitian Drive provides excellent exposures of cross bedded Eocene Carrizo sandstone. This fine-grained, noncalcareous sandstone is weakly consolidated and erodes easily when exposed. Examination of the roadcut shows that development of a soil (Alfisol) directly on the sandstone obliterates the primary sedimentary structures and increases both their clay and iron content. Farther west, lag gravels overlie the soil, which has been partly stripped in several places. The lag gravels thicken into a fonner gully now seen in cross section near the Tahitian Drive intersection. The Alfisol can

28

Page 34: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

be inspected closely in the eastern wall of the Tahitian Drive roadcut south of the Pahalawe Drive intersection.

The western wan of the Tahitian Drive roadcut provides excellent exposures of a complex local section. At the base is the Carrizo Formation, which is cross bedded; note, however, that while iron staining has enhanced expression of some beds it has also created "false bedding," which cuts across the true beds. Soft, light gray rip-up clasts are abundant in the Carrizo in parts of this exposure. These clasts were derived from clay drapes deposited during an interval of slack water. Overlying the Carrizo along a highly irregular contact there is a thin (-2 m) remnant of the channel deposits composing the Asylum/State Park Terrace fill. The coarsest clasts transported through the paleochannel lie directly on the contact, which represents the thalweg. The asymmetrical channel is seen in near perfect cross section (Le., perpendicular to the flow axis) and the contact rises both to the north and south. To the south, the terrace gravels become incorporated in the same Alfisol seen in the other roadcuts at this stop. The soil is developed in the gravels near the northern end of the channel fill, as well, but the contact there is steeper and the zone of overlap is narrow. Although the soil is moderately deep (to -1.5 m), it is clear that pedogenesis did not begin until the terrace was already highly degraded. The soil developed across the contact on both the channel-fill remnant and the truncated bedrock surface, which is almost a cut terrace. The age of the soil is therefore a poor indicator of the age of the terrace deposits, but may closely approximate the age of the landform. In addition, the Alfisol appears to have been truncated downslope by incision of the tributary channel, indicating that the soil pre-dates widespread dissection of the landscape. Across part of the roadcut, the Alfisol is buried beneath a thin (generally < 1 m) gravel lag. Gravel also mantles the sideslopes, beyond the present limit of the Alfisol. Obviously, the lag post-dates incision of the terrace remnant and appears to be a relatively recent deposit. This conclusion is corroborated by the weak horizonation of the thin soil covering the lag. Lag gravels serve to armor slopes, stabilizing them by reducing erosion. Indeed, this site provides a classic example of topographic inversion: the paleochannel bottom now forms the crest of the hill.

Stop 6. Highway 71 Gravel Pit.

At this stop we will briefly examine a thin mantle of iron-cemented fluvial gravels overlying differentially iron-cemented Eocene Carrizo sandstone. The section is exposed in a gravel pit on the south side of U.S. Highway 71 between Bastrop and Smithville, Texas (Figure 8). The terrace surface at this stop is 46 m (150 ft) above the low-flow channel of the Colorado River, and -49 m (160 ft.) below the highest bedrock "cut terrace" in this part of the valley (Figure 9, Table I). Although most of the gravel at this site appears to be a lag, there is a thin (-I m) remnant of fluvial­terrace fill retaining original sedimentary structures. Relief of this surface relative to the river places the site near the top of the relief range for Capitol Terrace equivalents in this reach (see Caran, this volume). If the fill had been 6 m (20 ft) thick, which is typical for the Capitol Terrace, the top of the terrace would have been 4.6 m (15 ft) higher than the observed relief of other Capitol Terrace relicts nearby. The importance of this seeming discrepancy cannot be evaluated at this time. Relief does increase downstream, however, and this site is the easternmost of the Capitol surfaces examined in this reach. If the relief range observed in the Smithville area is applied as the standard, the terrace at Stop 6 falls -3 m (10 ft) outside the range, which equals the contour interval on topographic maps used to record relief. This figure probably represents the limit of accuracy attainable by this method. The terrace at Stop 6 is therefore almost certainly a Capitol Terrace equivalent, which is here termed the Red Bluffs Terrace in this reach.

In addition to the terrace-fill remnant, the section exposed at Stop 6 reveals 6 m (20 ft) of tabular cross bedded Eocene Carrizo sandstone. Both the terrace fIll and the sandstone are iron cemented. Although access to the upper part of the exposure is limited at this site, the fill appears to be moderately indurated and cemented throughout. In contrast, the sandstone exhibits an unusual pattern of cementation. Ironstone developed along the unconformity bounding the Carrizo, but also extends downward along cross beds, which have moderate to steep dips.

29

Page 35: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Cementation was apparently following penneability contrasts related to minor variations in grain size on the lee slopes of large ripples. The site provides an example of the invasive nature of iron cementation in the unsaturated (vadose) zone. If cementation had resulted from diagenesis below the water table, the cement would have been dispersed throughout the porous medium. Variations of the type seen here are consistent with subaerial cementation, which could occur only after the water table was lowered, most likely after the terrace was created by valley incision.

Stop 7. Rehmet Volcanic Ash Locality/Ferris Sand and Gravel Pit. Stop 7 includes two sites in suburban Smithville, Texas (Figure 13). Although the terrace at

this locality is dissected, both sites lie between 32 and 35 m (105-115 ft) above the low-flow river channel, and -40 m (130 ft) below the highest surface in this part of the valley (Figures 14, l5, and16). The terrace at Stop 7 corresponds to the Capitol Terrace in Austin, the Red Bluffs Terrace in Bastrop, and the Oak Hill Terrace in Smithville. The Rehmet locality (Stop 7 A), on the west side of Easy Street, is the southernmost known occurrence of the Lava Creek B volcanic ash (620,000 yr B.P.). At Stop 7 A, the ash is interbedded with stacked upward-fining fluvial sands. These sands are correlative with deposits exposed in the western wall of the abandoned Ferris sand and gravel pit (Stop 7B) located east of Easy Street, -170 m (550 ft) east-southeast of the Rehmet locality. Both fine- and coarse-grained alluvium is exposed in the Ferris pit, but no volcanic ash has been found there.

Izelt and Wilcox (1982) reported the occurrence of Lava Creek B ash at the Rehmet locality (their site TX 2). Limited exposure of the ash prior to the present investigation prevented assessment of the possible relation of the ash to Colorado River terrace deposits exposed across Easy Street in the Ferris pit. In January, 1992, the present authors exposed the ash and terrace fill at the Rehmet locality and described and sampled the section (Figure 17). Samples were collected for detailed soil analysis and micromorphology, palynological and microtloral (diatom) analyses, and ash petrography. At the same time, Wulf Gose collected small, oriented samples for paleomagnetic analysis, and Ernest Lundelius, Jr., and Rickard Toomey collected bulk samples for paleofaunal analyses. Splits of samples representing the entire accessible section have been retained for future assessments. In the vicinity of Stop 7, the Togo 7.5-minute topographic quadrangle (Geological Survey, 1982), appeared to be in error: as shown on the map, the elevation at the approximate location of the ash bed seemed to be too low relative to other features in the landscape nearby. David Brown and Dan Julien conducted an alidade survey of the Rehmet locality and part of the Ferris pit to address this evident discrepancy. The survey line was run from Texas Highway 95 along Helkat Lane and Easy Street into both sites. This survey confirmed that the Togo map is in error. Actual elevation of the base of the ash bed is 115.7 m (379.6 ft) and the bed is 1.3 m (4.3 ft) thick. Izelt and Wilcox (1982) incorrectly reported the elevation of the ash as 110 m (360 ft).

Analysis of samples collected at the Rehmet locality in January, 1992, are partially complete. Results of the paleomagnetic analysis of samples from the terrace fill underlying the ash are summarized in Figure 18. This figure shows that samples from -2.1 m (7 ft) below the ash (almost 1.8 m below an artificial datum = 0 in Figure 18) to at least 2.9 m (9.5 ft) below the ash record an episode with reversed magnetic orientation, the Matuyama Chron. Figure 18 gives the age of the upper boundary of the chron as 720,000 yr , but this figure may soon be revised to 788,000 yr. The data indicate that a period of normal orientation from 910,000 to 970,000 yr may have been recorded by samples from deeper in the section. This infonnation, combined with the known age of the ash, indicate that the upper, relatively fine-grained part of the Capitol Terrace equivalent at this locality accumulated over a period of -350,000 yr, ending -600,000 years ago. This interpretation is consistent with the limited available paleofaunal record of the Capitol Terrace in the Austin area, which indicates that the terrace fill is less than 1,500,000 yr old (Lundelius, this volume; in press). The apparent absence of Bison sp.from the Capitol Terrace fill could be explained if the age of the fill is nowhere significantly younger than the Lava Creek B ash, which

30

\

)

)

)

, I

Page 36: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

/

~.~~~~.-~~~-T:~

" .

. J',

l,/ ol~ .J

Figure 13, Location map, Stops 7 and 8, showing lines of section E-E' and 0-0',

31

Page 37: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

!! "" c ii1 -!" E: " (,.) '<

I\) 0 a '" '" ~ g. :>

r;n t'!1

Terroco

ft RoDof m 160.---.41

S < Togo. TX mop I Smithville. TX map ~ Elev. (E) ...... of Lava Cr1<. B

N (E') 2

m It Hellcat ~. ""Iconic aah. Intetbeddod 400 with fluvial sand (southern

120., 1 ___ " J ,Rehmet extent undetennlnod)

lSI

100

30D

ao

Oak HUI cemetery ,ad

Colorado River valley

C~:-:~. of contact Broad "010 on flood terTac:. betwe.n PI.lotocon. fluvial depo.~ and Eocene Cook IItn. Fm. at Smith gravel pit 0.7 ml (1.1 km) NW af Rohm.t locality

(abandon.d chonnoJ Smlthvlll. IIKT

r of CoIOf'Qdo Rlver)"""\ (numerous _to) RR

J Hwy. 95

( uMamod trtbuto'l( IIKT RR of Willow Creok j

Topographic bas.: Togo. TX and Smlth"IJI •• TX 7.S-mln topographic quadrangle mapa (GeoJoglcaJ Survey. 1981; 1982). supplem.nted with data from an olldad. survey at the R.hmet locality. o 1 ml

I o km Vertical exaggeration: B6.6X

Quaternary terTace fIJI. overlying Eocene b.draclc (severol fonnotlons)

Elevation of hlghoot reported flood of Colorado RWor at

"ii o <>

Smltlwlll.. Oeo. 5(1) 105 1913 (Dalrympl. and l2 oth .... 1939. p. 280-281): 317.5 II (11.11 m).

1II027

U

1

65 20 .... 60

0'1

"-) ~il .1 .... ---'"- Ii: ill

4OD'2~j lO .i>

OL-.JO

".0: CO 00

"'.I:

Page 38: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

j

i

)

I

I J

l

"""r>;"., ':,\\ ,iii 0\f;:;t:;))~_Yr

Figure 15. Location map, Stop 7, showing line of section F-F'.

33

Page 39: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

E1ev. m It

180 -,

500

::!l 0<1

'" @ -9' 140

~ m

" Co) '< ..". (")

a '" '" ~ (") g. '" 'I1 , 'I1

120 400

350

100

W (F)

E (P)

l ........ land'ng otrip

Terrace

H5

r'5 It 2:~~

pvt. rd.

1'-1 Range In .... otfon at drainage cIvIde Hparatfng the Colorado RIver and Guadalupe RIver baalna E -8.5 ml (13.6 km) SN of the " Rehmet locollty (SN comer of I I ~ Togo topogrophlc mop). .:c

-4115 It unnamed tributary of WIllow CrHk '" 59

Topographic base: Togo. Texoa 7.S-mln topographic quadranvle mop (Geologlcol Survey. 1981). aupplemented with data from an aodad. survey at the Rehmet local~ and the Ferris grovel pll o I o Vertical exaggeration: 6a.aX

1 ml

km

Hwy. 535

Rehmet Ferri. locality 9rovel pIt (Stop 71.) (Stop 78)

WIllow pvt. WlUOW~ HwyEoay Creek rd. Creek 95 st.

~

Apprax .• Iev. of contact between PleIstocene fluvial deposita and Eocene Cook Mtn. Fm. at Smith gravel pit, 0.7 mi. (1.1 km) IfN of Rehmet locality.

180~48

i 8

105 J2

Page 40: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

: I

Figure 17. View of volcanic ash exposed in trench at the Rehmet Locality.

35

Page 41: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

o

2

tu 4 w u.

6

B

10

o

INCLINATION

9 0

20

N

o ,,"7 o ,0

1 " o •

+

oS

DECLINATION

21

20

19

1B

17

16

15

14

13 (J) »

12 s: " 11 r m

10 Z C

9 s: OJ m

B )J

7

6

5

4

3

2

1

Figure 18. Magnetostratigraphy of the Rehmet Locality and stereographic projection of the directions of magnetization. Solid circles are in the lower hemisphere, open circles in the upper.

36

Page 42: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

is 620,000 yr. Bison sp. is the diagnostic element of the Rancholabrean land-mammal fauna in North America, which is less than 300,000 yr old (Lundelius et al., 1987). No faunal material has yet been reCovered from either the Rehmet locality or the Ferris pit.

Samples of ash were submitted to Barbara Winsborough for identification of diatoms,and in contrast to the lack of preserved vertebrate remains, the ash contains a moderately diverse assemblage of fresh-water diatoms. Stratigraphic and sedimentological evidence indicates that the ash was transported to the Rehmet locality by the ancestral Colorado River after settling on the landscape from a huge ash cloud The thick ash bed probably accumulated in an oxbow lake or comparable environment with permanent water, where the diatoms flourished. A limited variety of palynomorphs were also recovered from the ash, including pine, sedge, and grass pollen. Other available analytical data are summarized below or completion of the analyses is pending.

The terrace fill underlying the ash consists of stacked upward fining thin beds of silty sand. These deposits represent periodic influxes of fluvial sediment settling in a relatively quiet-water environment, probably an oxbow lake. Several lines of evidence support this interpretation. The volcanic ash bed consists almost entirely of glass shards (largely undevitrified bubble-wall and bubble-junction shards) with very few detrital sand grains. The paucity of "contaminants" --typical fluvial sediments--from this bed can be explained by the likelihood that the air fall of volcanic dust blanketed the landscape, and was the first sediment then entrained by runoff and flushed into streams. A small lake would have been the ideal environment in which to accumulate a relatively pure ash bed under such conditions. In addition, the diatom micro flora includes several centric diatoms that are exclusively planktonic and are confined today to lakes, ponds, and large rivers (Barbara Winsborough, personal communication, 1992). Some of the diatoms are extremely delicate forms that could not have withstood aerial transport (from a proto Yellowstone Lake. for example). Finally, there are two modem examples of oxbow lakes--Shipp and Stagners Lakes--of the type inferred in an abandoned channel segment of the Colorado River less than 3.2 km (2 mil east of the Rehmet locality today. There seems little doubt that the ash bed is part of the terrace fill, and that it accumulated in a small lake or pond

The Ferris pit affords exposures of both fine- and coarse-grained sedi ment typical of Colorado River terrace fills. Section 1 in the Ferris pit is characterized by a 1.87 m thick upper unit of stratified, dark yellowish brown (lOYR 4/4, moist) to yellowish brown (lOYR 5/4, moist) fine­grained alluvium above a lower unit of stratified alluvial gravels. The surface soil was disturbed by the sand and gravel operation, but the subsoil is fairly intact (Table 7). The soil exposed in Section 2 is a red (2.5YR and 5YR hues) Paleustalf (Alfisol) developed in stratified sands and gravel (Table 8).

Stop 8. Clark Sand Pit and Archaeological Site.

At this stop we will examine fluvial and colluvial deposits associated with a low Pleistocene terrace of the Colorado River. The deposits are exposed in the walls of a large sand pit southeast of Smithville, Texas (FigureI4). Portions of the terrace surface are mantled with Holocene colluvium. and gullies cut into the Pleistocene deposits are filled with Holocene alluvium. The surface of the terrace is 18 m (60 ft) above the modem floodplain of the Colorado, and 56 m (185 ft.) below the highest surfaces in this part of the valley (Figure 19 and Table I). The terrace at the Clark site is correlative with the First Street Terrace in Austin, the Crafts Prairie Terrace in Bastrop, and the Shipp Lake Terrace (herein designated) in Smithville. We will focus on the south and west walls of the sand pit.

The lower 4 m of the section is largely composed of cross stratified sand with frequent lenses of gravel to small boulder size. Sands at the base of the section overlie gleyed, fine-grained alluvium exposed in the floor of the pit (Unit I). The sandy unit (Unit II) has a mixed mineralogy dominated by quartz, quartzite, and a wide variety of chert. Cross beds are seen in three dimensions, allowing reconstruction of paleo~urrent direction. Not surprisingly, sediment was

37

Page 43: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 7. Description of S""tion I at the F""';s Sand and Gravel Pit.

Depth Color Sbuc- Tex- Consis- Boun-Horizop (cm) Moist DIy lure !Ute tepee dary Special Features

Spoil Bt BCkl

BCk2

2C2

0-60 60-85 85-152

IOYR4/4 IOYR514

152-247 IOYRS/4

247-255+ 50% 7.5YR4/6 50% SYR4/6

2cP-I+2ABK If+mSBK

If+mSBK

M

CL SCL

SCL

fr fr

fr

GSCL fr

c,s c,S

a,s

Faint bedding; many fine pores coated with iron and manganese. Common fme faint 5YRS/4 mottles; 5% soft carbonate masses; few fine encrusted carbonate threads; faint bedding. Common medium and coarse distinctIOYR4I4, 10YRSI3, IOYR6/6, and 5YRS/4 mottles; complex redox accumulation and depletion patterns; 1-2% 2.5Y612 depletion zones; 10-15% soft carbonate masses; few very fine encrusted carbonate threads. Common large, round cobbles; stratified.

Abbreviations: Sbuclure: l=weak, 2=moderalc, 3=slrong, f=fine, m=medium, c=coarse, P=prismatic, SBK=subangular blocky, ABK=angu1ar blocky, GR=granular, M=massive Texture: S=sand, Si=sil~ C=clay, L=loom, V=very, F=fine, Co=coarse, G=graveUy Consistence: fi=f1Illl, fr=frlable, h=bard, v=very Boundaries: c=c1ear, g=gradual, a=ahrup~ s=smooth. w=wavy, i=irregular

Symbols: (+) and; (-) parting to

Page 44: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 8. o.scription of Section 2 at the Ferris sand and gravel pit

o.ptb Color Struc- Tex- Consis- Boun-Horizo.n (em) Moist Drv _ _ rure rure tence darv Soecial Features

Ap (H9 IOYR4/4 Abl 19-39 IOYR3/3 Ebl 39-49 IOYR4/4 Btsb2 49-67 70% 2.5YR4/6

30% 7.5YRSI6 Btsgb2 67-99 2.SY 612 exteriors

2.SYR4/6 interiors BCtsb2 99-134 SYR4/4

2C2 134-150+ IOYRS/4

2mSBK FSL fr 2mSBK FSL fr ImSBK FSL fr

2cP-2f+mSBK CL fr

2c+mP-3m+fAB C fr

2c+mSBK SC fr

M GeL fr

c,s Common fine roots. g,s Common fme roots; very few fine round pebbles. a,s Common fme roots; discontinuous stone line. e,s Few fme roots; common pressure faces.

e,s Faint 7.5YRS/6 aureoles; common distinct pressure faces; few large chert cobbles.

a,s Common thin, distinc~ continuous clay fibns on vertical ped faces.

Stone line composed of cobbles at top of horizon.

Abbreviations: Sb"Ucrure: l=weak, 2=moderate, 3=strong, f=fwe, m=medium, c=coarse, P=prismatic, SBK=subanguiar blocky, ABK=anguiar blocky, GR=granular, M=massive Texrure: S=sand, Si=silt C=clay, L=loom, V=very, F=fine, Co=coarse, G=graveUy Consistence:fi=frrm, fr=friable, h=bard, v=very Boundaries: c=clear, g=graduaI, a=abrup~ s=smootb, w=wavy, i=irregular

Symbols: (+) and; (-) parting to

Page 45: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

S E1ev. (G)

m It

:!l OQ c: ... '" J50 -'Ci

~ I 100

'" '< ~ 0 0 a

'" '" '" ~ 300

::to 0 ~

0 , 0

BO

Clark gravel pit (S~op

....

Colorado community

Togo. 1)( map I Smithville. 1)( map )

Colorado River valley Elwatlon of high •• reported flood of

Broad IIwal. on flood Colorado RIver at \elTQce (abandoned Smithville. Dec. 5(7)

.,...-chann.1 of Colorado RIver)...... 1913 (Dalrymple and ; 'loth .... 1939. p. 280-281):

L317.5 II (96.8 m).

Hwy. mad 71 -._0_.-._. 0_.

Topographic baa.: Togo. TX and Smithville. 1)( 7.S-mln topographic quadrangle mapa (GeologIcal Survey. 1981: 1982).

Quaternary terrace fill. overlying Eocen. bedrock. (nyeraJ formatlona)

N (G')

Terrace It Rolief m

9OD27~1 mm

65 20 611

rldg .. 40 and .. ale. JO

Col .... --II

'1 ILm

12L. .... 8~;:

.".c c" ....

o 1 ml

I water level \. I I I (low flOW) ~ t

• 0

md:

o Icm Vertical exaggeration: SS.8X

Page 46: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

j

j

transported from west to east through this area, just as it is today. A thick, red Paleustalf (Alfisol) is developed at the top of Unit II (Figure 20). This paleosol is

mantled with dark, silty colluvium and/or alluvium (Unit III) at most places along the pit walls. The Paleustalf has an Eb-BtIEb-Btsb-BCtsb profile (Table 9) that is completely leached of carbonates. The Eb2 horizon is 15 cm thick, pale brown (IOYR 6/3, dry) in color, and loamy sand in texture (Table 10). Bodies of E horizon material are common (15-25 %) in the upper part of the argillic (Btsb) horizon; hence, there is a 17 cm thick BtIEb transitional horizon. The Btsb2 horizon (Btslb2+Bts2b2) is 71 cm thick, yellowish red (5YR 4/6, moist) to red (2.5YR 4/6, moist) in color, and sandy clay loam in texture. There is distinct reticulate mottling in the Btslb2 horizon due to common light brownish gray (2.5Y 6/2) depletion zones along root paths. Patchy clay films occur on clasts and ped faces the BCtsb horizon, and red (2.5 YR 516), clayey lamellae are present in the BCtsb2 and 2C2 horizons. Thick strata of rounded chert cobbles are common below a depth of about 2.8 m.

Unit III is 50-75 cm thick across most of the section, and more than 2 m thick in some places where it occurs as gully fill. This unit consists of dark brown (IOYR 3/3 - 4/3, dry) loamy sand that forms a cumulic A horizon. There is a very high density of fire-cracked rock and chert flakes within the Alb and A2b horizons, and more than a dozen intact burnt-rock features (some stratified) have been documented in this unit. The recovery of a late-Paleoindian projectile point along with several Archaic points suggests that Unit III is a product of gradual sedimentation on a terrace surface that was frequently occupied by prehistoric ~ple through the Holocene.

Unit III is mantled by a thin veneer of slope wash (Umt IV). Unit IV is less than 25 cm thick, dark brown (IOYR 4/3, dry) in color, and loamy sand in texture. No cultural features or artifacts were found in this unit.

Preliminary Notes on the Clark Site by Alston V. Thoms

These notes result from a visit to the Clark site on March I, 1992, when Rolfe Mandel, Chris Caran, Pat Clabaugh, and I spent a couple of hours there the day after its discovery. Hence, what is written here is very preliminary and subject to considerable revision as we learn more and generate new data. Presently, we a completing a Texas "Archaeological Site Data Form," and developing plans for future investigations at the site.

The Genera! Nature of the Archaeolo~ical Record The site is exposed in the walls of a large gravel pit excavated into the scarp of a Pleistocene

terrace. Judging from our observations, the site limits extend well beyond the gravel pit. From an archaeological perspective, the most distinctive characteristics of the Clark site are its carbon­stained soils and sediments, and the high density of fire-cracked rock and chipped stone. Carbon­stained soils and sediments are not readily apparent on the highest part of the ridge crest, but on the lower parts they tend to extend from the surface to 0.40-l.0m below surface. Gullies cut into the Pleistocene alluvial deposits are filled with dark, artifact-rich sediments to depths of ca. 2.5m below the terrace surface.

Chipped stone artifacts, mostly from chert and chert-like stream-worn cobbles, along with some quartzite cobbles, occur in high densities on the slopes and floor of the gravel pit, and many items protrude from the pit's walls. Observed shipped-stone artifacts include cobble and bifacial cores (presumably from the local gravels), core reduction and biface thinning flakes, fragments of bifacial blanks and preforms, and a few edge-modified flakes. We collected three artifacts: (I) a complete teardrop-shaped preform (ca. 6.5 X 3.0 X 0.8 cm) from the cutbank, about 40cm below surface; (2) the distal end of a lancelot biface with a lenticular cross section and lamellar t1ake scars (ca. 6.0 X l.7 X 0.6 cm) from the talus at the base of the gravel pit wall; this specimen is probably a Late Paleoindian projectile point; and (3) a rectangular-shaped (ca. 7.1 X 3.8 X 1.4 cm) bifacial gouge-like tool (Clear Fork-like) from the cutbank about I m below surface, and near an

41

Page 47: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Figure 20. View of section exposed in west wall at the Clark Site.

42

I

I

j

I

Page 48: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 9. Description of Ibe west wall of Ibe Clark Site.

Depth Color Slruc- Tex- Consis- Boun-Horizon (cm) Moist Drv . rnr~ture tence darv S~ialEeatu=

Ap (}'23 IOYR312 IOYR413 Albl 23-62 10YR312 IOYR313 A2bl 62-88 IOYR3/3 10YR413 Eb2 83-103 IOYR4/3 JOYR613 BtlEb2 103-120 50% 7.5YR4/4

25% 5YR4/6 25% 7.5YR6/4

BISlb2 12(}'143 5YR4/6

BIS2b2 143-191 2.5YR4/6

BCISb2 191-286 75% 5YR4/6 10% 2.5YR4/6

2C2 286-336+ 7.5YR514

ImSBK LS fr Im+cSBK LS fr Im+cSBK LS fr ImSBK GLS fr 2m+fSBK FSL fr

2cP-2mSBK SCL fr

lcP-2mSBK SCL fr

ImSBK FSL fr

M GSL fr

C,s C,s C,s

a.i c.i

g,s

Common fme roots. Common fme roots; many fire-cracked rocks and lithic debilage. Common fine roolS; many flf<H:racked rocks and lithic debilage. Few IOYR313 bodies (10%); few fine roolS. E bodies compose 15-25% of matrix; few faint clay films on ped faces; few fme roolS.

Common thick, prominent 7.5YR412 clay films on vertical ped faces; 10% 2.5Y612 depletion zones along old root channels creating reticulate mottling patlem; few round, siliceous pebbles; Common fine bard ferromanganese concretions.

g,s Common thick, distinct 7.5YR5/4 clay ftIms on vertical ped faces; 1-2% 2.5Y612 depletion zones along old root channels creating reticulate mottling patlem; few lenses of round, siliceous pebbles; common fine bard ferromanganese concretions.

c,i Few thin 7.5YR5/4 clay mms on vertical ped faces; few clay bridges between sand grains; 1 (}'15 % 2.5Y 4/6 depletion zones along old root channels creating reticulate mottling pattern; few 2.5YR5/6 Iamellea 2-5mm thick; stratifted layers of SL + LFS; few fine bard ferromanganese concretions. Stratified; few 2.5YR5/6 lamellae; many round cobbles.

Abbreviations: Slructure: l=weak, 2=moderate, 3=strong, f=fme, m=medium, c=coarse, P=prismatic, SBK=subangular blocky, ABK=angular blocky, GR=granular, M=massive Texture: S=sand, Si=si\~ C=clay, L=loarn,V=very, F=fine, Co=coarse, G=gravelly Consistence: fi=finn, fr=friable, b=hard, v=very Boundaries: c=clear, g=gradual, a=abrup~ s=smoolb, w=wavy, i=irregular

Symbols: (+) and; (-) parting to

Page 49: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 10. Particle-size distribution: Clark Sire. limd* V. F. Sandi Clay free

HQ[lzQD Deillb VC C M E VF Total Sill CII): >2mm Ie&nG Eio!: SiIIld S ilD!.!lS UI - -cm- - - - - - - - - - - - - - - - - - - - - -wI. % - - - - - - - - - - - - - - - - - - - - - - - ------wt.%-----

Ap 0-23 9.0 16.9 20.9 26.1 14.4 87.3 9.5 3.2 13.0 LS Albl 23-62 5.7 11.6 22.0 29.2 ·16.3 84.8 ILl 4.1 11.0 LS A2b1 62-88 8.1 16.0 20.6 26.3 13.9 84.9 11.4 3.7 13.0 LS Eb2 88-103 8.1 12.9 19.7 26.3 16.5 83.5 12.3 4.2 17.0 GLS BtlEb2 103-120 5.2 12.0 16.3 25.5 16.7 75.7 129 11.4 12.0 FSL Brslb2 120-143 4.7 8.0 11.8 2Ll 16.1 61.7 12.9 25.4 3.0 SCL Brs2b2 143-191 \.6 4.8 11.2 25.2 17.4 60.2 15.2 24.6 1.0 SCL BCrsb2 191-286 5.2 7.9 10.0 19.9 23.2 66.2 16.2 17.6 12.0 FSL 2C2 286-336 13.8 15.9 16.9 18.1 12.1 76.8 10.1 13.1 26.0 GSL

*Partic1e-size Iimirs (nun): Sand: VC = 2.0-1.0, C = 1.0-0.5, M = 0.5-0.25, F = 0.25-0.10, VF = 0.10-0.05 Sill: Total = 0.05-0.002, Fine = 0.02-0.002 Clay: Total = < 0.002, Fine = <0.0002

"fexlUre ciasses: S=sand, Si=sill, C=clay, L=loam, V=very, F=fine, Co=coarse, G=gravelly. ex=exrremely, v=very

055 0.9 056 8.0 052 8.0 0.63 7.2 0.65 6.1 0.76 4.8 0.69 3.9 1.16 4.2 0.67 8.0

Page 50: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

)

)

intact lens of fire-cracked rock. There are numerous lenses of fire-cracked rock (ca. 10-20 cm thick and 0.40-2.0 m long)

exposed in the walls of the gravel pit. Most of these occur within the upper I m of sections, but in one place where the dark sediments extend to about 2.5 m b~low surface (gully fill), there were two superimposed lenses between about I and 2 m below surface. None of the features appear to be associated with buried soils, but the carbon-staining and bioturbation of the sandy sediments may well have masked soil boundaries. Most of the rock lenses seemed to be composed of quartzite and some chert cobbles ranging from about 7 to 15 cm in maximum dimension, but a few of the cobbles were somewhat larger. The rocks tend to be fire-cracked, heat-spalled, and reddened. In several cases, a charcoal-rich deposit appeared to underlie the rock lenses. How these features functioned is not clear, but they may represent some kind of earth oven or hearth facilities.

Comments on Possible Site Function

When we visited the site, I tried to "see" it as some kind of burned rock midden deposit like those found throughout much of central Texas. It had plenty of fire-cracked rock (FCR) and chipped stone artifacts, including several Archaic age projectiles points collected by a nearby resident. The sediments were dark enough', and the setting on a high terrace scarp above bottomlands was typical of burned rock midden sites in the region (cf Hester 1991). There were. however, other characteristics not necessarily typical of burned rock middens:

I. The FCR is primarily quartzite and chert, rather than limestone.

2. With the exception of numerous lenses of FCR, clast supported FCR is not common anywhere in the gravel pit profile.

3. The extent of the carbon-stained sediments is greater than expected.

4. Much of the chipped stone is fire-cracked, glazed, or discolored, suggesting that it may have been used as some type of hearth stone, or perhaps that it was one of the components of a burned "kitchen midden," or perhaps that it had been intentionally heat-treated.

5. A higher than expected proportion of the chipped stone appears to represent the initial stages of lithic reduction, suggesting that tool manufacturing was a major activity at the site.

6. We did not find much in the way of lithic artifacts characteristic of camp debris, e.g., broken points, scrapers, grinding tools, or expediency tools.

7. We did not observe any faunal material.

Collectively, these characteristics suggested that the site might not be a burned rock midden deposit. Neither the artifacts or features seem to be consistent with my ideas about what a typical base camp or hunting site should look like.

The extensiveness of the site's carbon-stained and FCR-rich sandy sediments is reminiscent of sites in parts of the Pacific Northwest where, for thousands of years, root foods (e.g. camas, Camassia auamash) were bulk-processed in large earth ovens with rock heating elements (Thoms, 1989). Similar plant processing sites, but without much FCR, are reported from southern Africa as well (Deacon, 1976). In fact, there are FCR-rich sites throughout the world with carbon-stained sediments and large earth over-like features that may have been places where plants foods were bulk-processed (Thoms, 1989).

For the Clark site, what is important is that carbon-stained soils and sediments seem to be characteristic of places where many earth ovens were built and used through the decades,

45

Page 51: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

centuries, or millennia. Loose, sandy sediments are especially prone to being "coated" by carbon (Le., soot) when the fire for an earth oven is burning in the open air, as well as when the charcoal continues to burn after the earth oven is loaded and closed (Le., capped with an earth cover).

Unlike the Clark site, plant food bulk-processing sites tend to be chipped stone-poor (Thoms, 1989). Nonetheless, while most Texas burned rock midden sites probably were plant food processing places, it is clear that in many cases other subsistence and camp maintenance activities were carried out there as well. To the extend that hunting-related, plant processing, and camp maintenance tools, as well as food remains, turn out to be uncommon at the Clark site, as they appeared to be upon initial inspection, this site appears to be atypical in comparison to the more "typical" site types in the region.

A Workini Model for Site Function At the Clark site, tentative evidence and "working" ideas about site function include the

following:

1. There is an apparent high density of chipped stone artifacts characteristic of the early stages of bifacial lithic reduction.

2. Many of the chipped stone artifacts appear to be "cooked" or over-cooked.

3. The lenses of FCR are structurally similar to heating elements in earth ovens ranging in diameter from about 0.5 to 2 m or more.

4. The extensiveness of the carbon-stained soils and sediments may be a byproduct of the intensive use of earth ovens.

What this tentative evidence suggests is that the Clark site may be a place where hundreds, if not thousands, of earth ovens were built and used to heat-treat locally available chert cobbles and other lithic materials. Heat-treating lithic material in earth ovens to render it more knapable is well­documented in the ethnographic record, and to a lesser extend in the archaeological record (e.g., Hester, 1972,1977; Johnson 1978). In my quick literature review, I did not find a discussion of rock lenses (i.e., heating elements) in the earth ovens used to heat-treat lithic raw material. Additional research, however, is likely to improve the working data base

Concludins Comments Exploratory excavations should yield the kinds of data needed to assess the working model for

bulk-processing lithic raw materials, as well as other models for different kinds of site function. Assemblage comparisons of artifacts and features should also be made among the Clark site, burned rock midden sites, and other site types in the region. Given the carbon-stained soils and sediments at the Clark site, it should be possible to obtain reliable age estimates on a sample of the features. Stratified cultural deposits in the more deeply buried parts of the site promise an added measure of chronological control. The temporally diagnostic artifacts characteristic of the Late Paleoindian and Archaic periods already suggest long-term use of the site, although site function may have varied considerably through time. Judging from the presence of numerous intact features in the active bioturbation zone, the site may have been used during the Late Prehistoric period as well.

46

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SUNDAY, MARCH 29, STOP 1

GENESIS OF THE QUIHI SOIL IN THE UVALDE GRAVEL OF SOUTH-CENTRAL TEXAS

L.E. LOOMIS, W.l. GABRIEL, AND B.R. BRASHER

ABSTRACT The Quihi soil fonned in stratified bedload channel alluvium of the Uvalde

Gravel. The limestone sands, gravels, and cobbles were probably the primary source of carbonate that fonned the petrocalcic horizon. Evapo-transpiration is thought to cause the upward movel11ent of soil solutions. Aqueous carbonates precipitate and accumulate near the site of water withdrawal. Chert clasts constitute most of the layers above the petrocalcic horizon, whereas solution-facetted limestone pebbles occur within and below it. The red, clayey argillic horizon suggests intense weathering, with residual and illuvial concentration of non-carbonate residue.

INTRODUCTION

The Quihi (pronounced kwee-hee) soil at Stop I near Castroville, Texas, is developed in the Uvalde Gravel Formation. The soil (Figure I), which occurs on stable, chert-armored surfaces with less than 8 percent slope, formed during an extended period of landscape stability (Gustavson, 1988:66). The Quihi soil series, established in 1972 during field work for the soil survey of Medina County (Dittmar et al., 1977), has also been mapped in Guadalupe County (Ramsey and Bade, 1977). Total area of the map units of Quihi soils is 8825 hectares in Medina County and 440 hectares in Guadalupe County.

Mean annual precipitation at Hondo, Texas, 21 km west, is 72 cm, and the mean annual air temperature is 20.4 degrees C. Eastern Medina County has an annual Precipitation-Effectiveness index of 40 (Thornthwaite, 1931). The seasonal distribution of precipitation and temperature, as well as potential evapo-transpiration and a soil water balance as computed by the Newhall Simulation Model (Van Wambeke et al., 1986) are illustrated in Figure 2. The classification of the soil moisture regime is Ustic, the soil temperature regime is Hyperthermic. Currently, the taxonomic placement of the Quihi series is clayey-skeletal, mixed, hyperthermic Petrocalcic Paleustolls (Table 1).

A morphological description of the Quihi pedon (Figure 1) sampled on a caliche pit face is given in Table 2. Results of physical, chemical, and mineralogical analyses performed by the National Soil Survey Laboratory of the Soil Conservation Service are in Table 3. Table 4 presents particle size distribution in the Quihi soil on a clay-free weight basis. Erosion or excavation partially truncated the A horizon (Sample 7928), so an intact A horizon (Sample 7934) was sampled about 16 m northwest of the sampled pedon location.

UVALDE GRAVEL

Early studies (Hill, 1891, Plummer, 1933) did not distinguish the Uvalde Gravel from the Goliad Formation in South Texas. The Goliad Formation, originally described and discussed under the name Reynosa Formation (Price, 1933:488; Deussen, 1924; Trowbridge, 1932), crops out in a broad belt along the South Texas Gulf Coastal Plain from Starr County to Lavaca County. Earlier maps of the Reynosa Fonnation (Price, 1933:490) included areas of so-called "Up-dip Reynosa". These areas are now recognized as the Uvalde Gravel (Brown et al., 1983).

Page 53: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

.~ . -, , .

-!," ~. , ,i~.,

'. ~.:.1- ~;' 1t ....... ,

,I 1:.' .~,

I

Figure l. Photo of the pedon.

Page 54: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Figure 2. Climatic daIa and soli water balance for Hondo, Texas em

25

20

15

10

5

--- '" '"

u

... ---, , , , , \

D \ \

\ .\

........ R ....

c

30

20

10

o

-10

o I I -20 J D

U,I ..... ; D,DIIcIt; R, RechIuge; s, SurplUs; PrecIp. PE - T8I'I1).

Page 55: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table h. Classification of the Soil Series Mentioned in the Text.

Series- Family

Bexar Comfort Crawford Cuevitas Dina Hensley Hindes Jimenez Mercedes Moglia Montell Olmos Quemado Quihi Randado Rumple Roughcreek Spec]< Spires Tarpley Valco Victoria Yologo Zapata

Fine, mixed, thermic Typic Argiustolls Clayey-skeletal, mixed, thermic Lithic Argiustolls Fine, montmorrillonitic, thermic Udic Chromusterts Loamy, mixed, hyperthermic, shallow Ustollic Paleorthids Clayey-skeletal, mixed, thermic Pachic Paleustolls Clayey, mixed, thermic Lithic Rhodustalfs Clayey-skeletal, mixed, hyperthermic Aridic Argiustolls Loamy-skeletal, mixed, hyperthermic, shallow Petrocalcic Calciustolls Fine, montmorrillonitic, hyperthermic Udorthentic Pellusterts Fine-loamy, mixed, hyperthermic Ustollic Calciorthids Fine, montmorrillonitic, hyperthermic Entic Pellusterts Loamy-skeletal, carbonatic, hyperthermic, shallow Petrocalcic Calciustolls Loamy-skeletal, mixed, hyperthermic, shallow Petrocalcic Ustalfic Paleargids Clayey-skeletal, mixed, hyperthermic Petrocalcic Paleustolls Loamy, mixed, hyperthermic, shallow Petrocalcic Ustollic paleargids Clayey-skeletal, mixed, thermic Udic Argiustolls Clayey-skeletal, montmorrillonitic, thermic Lithic Argiustolls Clayey, mixed, thermic Lithic Argiustolls Fine, mixed, thermic Rhodic Paleustalfs Clayey, montmorrillonitic, thermic Lithic Argiustolls Loamy, mixed, hyperthermic, shallow Petrocalcic Calciustolls Fine, montmorrillonitic, hyperthermic Udic Pellusterts Loamy-skeletal, mixed, hyperthermic, shallow Petrocalcic Paleustolls Loamy, mixed, hyperthermic, shallow Ustollic Paleorthids

Page 56: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 2. Description of the Quihi soil.

USDA - Soil Conservation Service Pedon Narrative Description Soils Series: Quihi NSSL IDt: 9lPl188 Soil Survey t S91-TX-325-001 Map Unit Symbol: QUC Photo Number: 41 Description Type: full pedon description Pedon Type: Within range of series Geographically Associated Soils: Olmos Location: From into of US 90 and FM 1343 W of Castroville, 0.15 mi E on frontage road past Glenford Boehme home, then 0.3 mi SSW to Wend of gravel pit Latitude: 29-20-38-N Longitude: 098-53-48-W Classification: clayey-skeletal, montmorillonitic, hyperthermic Petrocalcic Paleustoll Geomorphic position: shoulder of an interfluve Slope Characteristics: 3% northeast facing convex horizontal, convex vertical Elevation: 293 m MSL Precipitation: 72 cm ustic moisture regime MLRA: 83A Air Temperature: Ann 20 C Sum 29 C Win 12 C Drainage Class: well drained Land Use: rangeland grazed Erosion: moderate Runoff: moderate Particle Size Control Section: 8 to 75 cm Parent Material: alluvium from limestone-cherty material Diagnostic Horizons: 0 to 41 cm mollic, 8 to 54 cm argillic, 54 to 74 cm calcic, 74 to 153 cm petrocalcic Described By: W.J. Gabriel and L.E. Loomis Date: 08/91 Notes: Live oak, agarito, pricklypear, huisache, brasil, whitebrush, persimmon, blackbrush, red grama, hairy tridens, threeawn, ~ilver bluestem, fall witchgrass, King Ranch bluestem, annual broomweed, croton, dogweed, indianmallow, tubetongue, frostweed, orange zexmania, bundleflower. Unbroken chert fragments have white (10YR 8/1) and pinkish white (7.5YR 8/2) weathering rinds 4 to 8 mm thick. Pinkish white colors are more common on outermost rinds and may contain oriented clay.

A--O to 13 centimeters; this horizon was described and sampled about 50 ft NW of pedon to determine characteristics of an undisturbed surface; very dark gray (10YR 3/1) gravelly silty clay loam; black (10YR 2/1) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky, moderately plastic; many very fine and fine roots throughout; common very fine and fine tubular, and many very fine interstitial pores; about 60% of chert fragments are broken and have no weathering rinds; about 40% of chert fragments have pinkish white (7.5YR 8/2) weathering rinds up to 3 mm thick; many prominent very dark gray (10YR 3/1) continuous clay films (cutans) on rock fragments;

Page 57: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 2 (continued). Description of the Quihi soil.

15% chert pebbles; 10% chert cobbles; clear smooth boundary.

A--O to 8 centimeters; dark reddish gray (5YR 4/2) extremely gravelly clay; dark reddish brown (5YR 3/2) moist; moderate very fine subangular blocky structure; slightly hard, friable, moderately sticky, moderately plastic; many very fine and fine roots throughout; common very fine and fine tubular, and many very fine interstitial pores; horizon is thinner and lighter in color than in pedons on more stable surfaces; rock fragments cover 80% of soil surface (5% cobbles, 75% pebbles); effervescence ranges from slight to strong; horizon may have been recalcified when gravel pit was in active use; many prominent dark reddish brown (2.5YR 3/4) continuous clay films (cutans) on rock fragments; few fine cylindrical worm casts; slightly effervescent; neutral (pH 7.2); 60% chert pebbles; 5% chert cobbles; clear smooth boundary.

Bt--8 to 41 centimeters; dusky red (2.5YR 3/2) extremely gravelly clay; dusky red (2.5YR 3/2) moist; strong very fine and fine angular blocky structure; very hard, very firm, very sticky, very plastic; many very fine and fine roots throughout; common very fine and fine tubular, and many very fine interstitial pores; cobbles are concentrated at base of horizon; horizon might be fragmental if not for worm fecal pellets; many prominent dark red (2.5YR 3/6) continuous clay films (cutans) on rock fragments; few fine cylindrical worm casts; mildly alkaline (pH 7.7); 70% chert pebbles; 5% chert cobbles; abrupt wavy boundary.

Btss--41 to 54 centimeters; 25% weak red (2.5YR 4/2) exterior, and 75% reddish brown (2.5YR 4/4) clay; 25% dusky red (2.5YR 3/2) exterior, and 75% dark reddish brown (2.5YR 3/4) moist; strong medium and coarse angular blocky structure; extremely hard, very firm, very sticky, very plastic; common very fine and fine roots between peds, and common very fine and fine roots throughout; common very fine and fine tubular, and very fine interstitial pores; common wedge-shaped aggregates 2-3 cm in long dimension; mollic colors are mainly on faces of slickensides; few intersecting slickensides, few distinct black (10YR 2/1) patchy organic coats on faces of peds, and many prominent continuous clay films (cutans) on rock fragments; mildly alkaline (pH 8.0); 7% chert pebbles; abrupt irregular boundary.

Btk--54 to 74 centimeters; dark reddish brown (5YR 3/3) extremely gravelly clay; dark reddish brown (5YR 3/3) moist; moderate fine and medium subangular blocky structure; hard, friable, moderately sticky, moderately plastic; common very fine and fine roots throughout; common very fine and fine tubular,

Page 58: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 2 (Continued) Description of the Quihi soil.

and. common very fine interstitial pores; upper surfaces of limestone pebbles are solution faceted; about 10% by volume weakly to strongly cemented CaC03 pendants on lower sides of limestone pebbles; few distinct light brown (7.5YR 6/4) patchy lime or carbonate coats on lower surfaces of stones; many prominent continuous clay films (cutans) on rock fragments; few fine cylindrical worm casts; strongly effervescent; mildly alkaline (pH 7.8); 30% limestone pebbles; 35% chert pebbles; abrupt wavy boundary.

Bkml--74 to 88 centimeters; 55% pink (7.5YR 8/4), and 45% pinkish white (7.5YR 8/2) very gravelly weakly cemented caliche; 55% pink (7.5YR 7/4), and 45% pinkish gray (7.5YR 7/2) moist; massive; weakly cemented by lime; few very fine and fine roots in cracks, and few medium roots in cracks; upper 1 cm is indurated, next 1 cm is strongly cemented; upper surfaces of limestone fragments are solution faceted; strongly cemented CaC03 pendants up to 3 cm thick occur on lower surface of limestone fragments; violently effervescent; moderately alkaline (pH 8.3); 15% limestone pebbles; 2% limestone cobbles; 15% chert pebbles; 3% chert cobbles; gradual wavy boundary.

Bkm2--88 to 153 centimeters; 98% pinkish white (7.5YR 8/2), and 2% red (2.5YR 4/6) very gravelly weakly cemented caliche; 98% pinkish white (7.5YR 8/2), and 2% red (2.5YR 4/6) moist; massive; weakly cemented by lime; few very fine and fine roots in cracks, and few medium roots in cracks; upper surfaces of limestone fragments are solution faceted; strongly cemented CaC03 pendants up to 3 cm thick occur on lower surfaces of limestone fragments; common medium and coarse cylindrical clay bodies; moderately alkaline (pH 8.1); 22% limestone pebbles; 5% limestone cobbles; 22% chert pebbles; 7% chert cobbles.

Page 59: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 3. Laboratory Data for the Ou1hi Profile.

*** P RIM A R Y C H A R ACT E R I Z A T ION D A T A ***

S9lTX-32S-001 (MEDINA COUNTY, TEXAS

PRINT DATE 02/06/92 SAMPLED AS : QUIHI ; CLAYEY-SKELETAL, MIXED, HYPERTHERMIC PETROCALCIC PALEUSTOLL NSSL - PROJECT 91P 191, SOUTHERN F.O.P. U. S. DEPARTMENT OF AGRICULTURE - PEDON 9lP1188, SAMPLES 9lp7928-7936 SOIL CONSERVATION SERVICE - GENERAL METHODS lBlA, 2Al, 2B NATIONAL SOIL SURVEY LABORATORY LINCOLN, NEBRASKA 68508-3866

-1-- -2-- -3-- -4-- -5-- -6-- -1-- -8-- -9-- -10- -11- -12- -13- -14- -15- -16- -11- -18- -19- -20-

(- - -TOTAL - - -) (- -CLAY- -) (- -SILT- -) (- - - -SAND- - -) (-COARSE FRACTIONS (KH)-) (>2KH) CLAY SILT SAND FINE C03 FINE COARSE VF F H C VC - - - - WEIGHT - - - - WT

SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF NO. (CM) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -15 15 WHOLE

(- - PCT OF <2MM (3A1) - - - -> <- PCT OF <75MM(3Bl)-> SOIL 91P1934S 0- 13 A 33.3 34.2 32.5 9 11.2 11.0 19.0 9.4 2.2 1.3 0.6 1 24 24 56 49 91P1928s 0- 8 A 53.2 23.6 23.2 16.0 1.6 1.2 5.9 2.1 3.0 4.4 1 56 1 10 64 91P1929S 8- 41 BT 65.8 11.8 22.4 8.8 3.0 2.9 1.1 0.8 2.9 14.1 10 62 11 12 91P1930s 41- 54 BTSS 66.0 21.1 12.9 1 11.1 3.4 4.9 1.0 1.5 2.8 2.1 1 3 2 i4 6 9lP7931S 54- 14 BTK 53.1 23.1 23.2 1 14.4 9.3 4.6 3.3 3.4 4.4 1.5 9 53 69 62 91P1932S 14- 88 BKH1 10.9 29.8 59.3 6 20.5 9.3 6.3 10.1 11.4 15.5 16.0 53 91P1933G 88-153 BKH2 11. 4 33.6 55.0 1 24.1 9·5 5.5 9.8 10.6 13.1 16.0 49 --P -----------------------------------------------------------------------------------------------------------------------------------

DEPTH (eM)

0- 13 0- 8 8- 41

41- 54 54- 14 14- 88 88-153

ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -I (RATIO/CLAY) (ATTERBERG ) (- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD C N P S EXTRACTABLE

FE AL MN 6AIC 6B3A 6S3 6R3A 6e2B 6G7A 6D2A PCT <2MM PPM <- PERCENT OF <2HM --> 2.59 0.201 2.23 0.185 1.18 0.145 1.29 0.124 1. 13 0.114 0.15 0.014 0.13 0.011

AVERAGES, DEPTH 8- 58: PCT CLAY 64 PCT MMHOS/CM OF 1:2 WATER EXTRACT (81) FOR LAYERS ANALYSES: Sz ALL ON SIEVED <2MM BASIS

15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE CEe BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL 8D1 8Dl 4F1 4F 4A3A 4AID 4AIH 4D1 484 4BIC 4BIC 4B2A 4e1

PCT <O.4MH <- - G/CC - - -> eH/eH <- - -PCT OF <2MM - -> CHICH 0.93 0.48 16.1 0.83 0.45 23.9 0.11 0.48 31. 4 0.83 0.51 33.4 0.16 0.49 26.1 0.35 0.48 5.2 0.27 0.35 4.0

.1-75HH 60 2, 3, 5, Gc <2MM ON GROUND <7SMM BASIS p= FABRIC ON <7SMM FRACTION

Page 60: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 3 (Continued). Laboratory Data for the Quihi Profile.

••• P RIM A R Y C H A R ACT E R I Z A T ION OAT A ... s91TX-325-001 PRINT DATE 02/06/92 SAMPLED AS : QUIHI ; CLAYEY-SKELETAL, MIXED. HYPERTHERMIC PETROCALCIC PALEUSTOLL

; PEDON 91Pl188. SAMPLE 91P7928-7936 NATIONAL SOIL SURVEY LABORATORY -1-- -2-- -3-- -4-- -5-- -6-- -7-- -8-- -9-- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

DEPTH ICM)

0- 13 0- 8 8- 41

41- 54 54- 74 74- 88 88-153

DEPTH ICM)

0- 13 0- 8 8- 41

41- 54 54- 74 74- 88 88-153

(- NH40AC EXTRACTABLE BASES -) ACID-CA MG NA K SUM ITY

5B5A 5B5A 5B5A 5B5A BASES 6N2£ 6020 6P2B 6Q2B <- - - - -MEQ { 100 29.6 3.2 1.2 0.8 34.8

2.4 0.2 1.0 59.7 3.3 0.5 0.9 64.4

2.7 1.0 0.8 1.9 1.6 0.6 0.6 0.6 TR 0.6 1.4 TR

6HSA G - -2.6

3.6

1- -CEC- -) SUM NH4-CATS OAC 5A3A SASB

- -> 37.4 31.0

43.9 68.0 50.6

54.5 40.4 3.8 3.1

1- - - - -WATER EXTRACTED FROM SATURATED PASTE-

CA MG

6N18 6018 < - - -

5.8 0.9 7.5 0.4

6.2 0.4

9.8 0.8

NA K C03 HC03 CL S04 N03

6P1B 6QIB 6I1B 6J1B 6K1C 6L1C 6M1C - - -MEQ 1 LITER - - - >

0.4 0.3 5.1 0.8 1.0 0.3 0.1 6.2 0.5 0.7

0.7

4.3

0.1

0.2

4.5

1.1

0.7

9.3

1.0

3.1 1.7

EXCH NA

5B5B PCT

4 1 1 2 4

16 42

SAR

5E

TR TR

TR

2

BASE SATURATION

SUM NH40AC SC3 SC1

<- -PCT- > 93 100

95 100

CARBONATE AS CAC03

<2MM <20MH 6E1G 8E1 <- -PCT ->

TR 6 1 9

32 82 85

CAS04 AS GYPSUM

<2HM <20MH 6F1A 6F4 <- -PCT ->

1- -SAT

PASTE 8C1B

6.8 7.3

7.3

7.8

- -PH CACL2

.01H 8c1F 1:2 7.3 7.0 7.2 7.4 7.3 7.7 7.8

- - -) H20

SC1F 1:1 8.8 7.2 7.7 8.0 7.8 8.3 8.1

- - -) 1- - - - - - -MINERALOGY - - - - - - - - -) TOTAL ELEC. 1- - - - - CLAY - - - - - - -) 1- - -) -)

H20 SALTS CONDo (- - X-RAY - - - -) (- - - - - -) TOTAL DOH EST. 8A3A (- - - - - <2U - - - -) RES WEATH

8A 805 MMHOS 7A2I 7A2I 7A2I 7A2I 7A6 7A6 7B1A 7B1A <- -PCT -> {CM <- RELATIVE AMOUNTS -> <- - - - -PCT - - - -> 52.5 TR 0.67 HT 2 HI 2 KK 2 MM 2 80 FK18 68.1 TR 0.76 MT 2 VR 2 MI2 KK 2

70.8

21.2

0.02 MT 2 VR 2 MI 2 KK 2 0.22 MT 3 MI 2 MM 2 KK 2

TR 0.67 MT 3 MI 2 KK 2 MM 2 0.16 CA 3 KK 1 MI 1

TR 1.62 CA 3 HI 1

84

40 S 9

FKll

CA58 CA58 CAS7

MINERALOGY: KIND OF MINERAL MT MONTMORILL VR MM MONT-MICA CA

VERMICULITE CALCITE

HI MICA KK KAOLINITE FK POTAS-FELD

RELATIVE AMOUNT 6 INDETERMINATE S DOMINANT 4 ABUNDANT 3 MODERATE 2 SMALL 1 TRACE

Page 61: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 3 (Con~inued). Laboratory Data for the Quihi Profile.

••• P R I H A R Y C H A R ACT E R I Z A T ION D A T A .. . s91TX-325-001 (MEDINA COUNTY, TEXAS J

PRINT DATE 02/06/92 SAMPLED AS : QUIHI ; CLAYEY-SKELETAL, MIXED, HYPERTHERMIC PETROCALCIC PALEUSTOLL NSSL - PROJECT 91P 191, SOUTHERN F.O.P. U. S. DEPARTMENT OF AGRICULTURE - PEDON 91P1188, SAMPLES 91p7928-7936 SOIL CONSERVATION SERVICE - GENERAL METHODS IBIA, 2AI, 2B NATIONAL SOIL SURVEY LABORATORY LINCOLN, NEBRASKA 68508-3866

-1-- -2-- -3-- -4-- -5-- -6-- -7-- -8-- -9-- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

< - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mmJ - - - - - - - - - - - - - - - - - - - - > FRACT < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - OPTICAL - - - - - - - - >< > INTER

DEPTH ION < >< - OTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< > PRETA < - - 7A2i - - - - >< - 7A3b - >< - 7A4b - >< 7Bla - - - - - ->< > TION

(cm) < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - Percent - - - - ->< - - - - - - - ->< - -> 0- 13 CS, 80 QZ73 FK18 PO 4 OP 2 PR 1 CD 1 0- 13 CSi CA 1 AHtr CBtr BTtr TMtr HStr 0- 13 CS, GStr 8- 41 Csi 84 QZ77 FKll OP 4 CD 3 PR 2 HS 1 8- 41 cSi BT 1 FP 1 POtr ZRtr GNtr TMtr 8- 41 csi CAtr AHtr

54- 74 CSi 39 CA58 QZ35 OP 3 FK 2 CD 1 CB 1 54- 74 CSi POtr GStr HStr BTtr TMtr 74- 88 cst 5 CA58 CB37 QZ 4 CD 1 OPtr BTtr 74- 88 cst THtr FKtr 88-153 CSi 9 CAS7 CB34 QZ 7 CD 2 OPtr ZRtr 88-153 CSt PRtr MStr FKtr GStr

KIND OF MINERAL: HT montmorl1I VR vermiculit.e HI mica KK kaolinite MH mont-mica QZ quartz Ai FK potas-feld OP opaques CD chalcedony PR pyroxene MS muscovite BT biotite FP plag-feld PO plant opal ZR zircon GN garnet TM tourmaline CA calcit.e AM amphibole HE hematite CB carb-aggreg GS glass AO

Page 62: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 4. Particle Size Distribution on a Clay-Free We1gh~ Basis

S91TX-325-001 SAMPLED AS NATIONAL SOIL

PRINT DATE 02/06/92 : QUI HI; CLAYEY-SKELETAL. MIXED. HYPERTHERMIC PETROCALCIC PALEUSTOLL SURVEY LABORATORY ; PEDON 91Pl188. SAMPLE 91P1928-7936

-1-- -2-- -3-- -4-- -5-- -6-- -7-- -B-- -9--( WEI G H T F R ACT ION S - C LAY F R E E ) --W H 0 L E SOl L-- ---<2 HH F RAe T ION ----

SAMPLE DEPTH >2 75 20 2- .05- LT ------SANDS------- SILTS CL NO (CH) -2 -2 .05 .002.002 VC C H F VF C F AY

917934 0- 13 91792B 0- B 917929 B- 41 917930 41- 54 917931 54- 74 917932 74- BB 917933 BB-153

PCT OF >2HH+SAND+SILT> (------PCT OF SAND+SILT------) 76 77 7B 79 BO Bl B2 B3 B4 B5 B6 B7 BB B9

59 59 30 20 21 20 1 2 3 14 2B 25 26 50 79 79 7B 10 11 24 9 6 6 13 15 16 34 114 BB BB BB B 4 23 41 B 2 5 B 9 26 192 16 16 11 32 52 163 B B 4 3 14 10 52 194 7B 7B 7B 11 11 25 16 9 7 7 10 20 31 113

67 33 12 IB 17 13 11 7 10 23 12 62 3B 13 IB 15 12 11 6 11 27 13

-------------------------------------------------------------------------

Page 63: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

The Uvalde Gravel deposits north of the Colorado River and those along the Rio Grande contain clasts that originated in the Southern Rocky Mountains of New Mexico, Mexico, and the Trans-Pecos area of Texas (Byrd, 1971). Purplish quartzite and brown jasper were observed in Uvalde Gravel deposits in Kinney County (Bennet and Sayre, 1962:58). Clasts of chert, limestone, and jasper, and tan, yellow, and purple quartzite were observed in Bosque County (Byrd, 1971). However, Uvalde Gravel deposits located on the Rio Grande Plains downdip of the Balcones Escarpment between New Braunfels and Brackettville, including those at Castroville, are composed entirely of limestone and chert fragments derived from the Edwards Plateau.

The present distribution of the Uvalde Gravel in the Rio Grande Plain (mapped by Brown et al., 1983; Brown et al., 1976; Brewton et al., 1976) is only a remnant of a much larger alluvial plain deposited during the Miocene and Pliocene. Areas of Quihi, Olmos, Zapata, Jimenez, Quemado, Hindes, Yologo, Cuevitas, Randado, Moglia, Mercedes, Victoria and Montell soils (Thble 1) on hillcrest and summit landscape pOsitions, as delineated on soil survey maps (Stevens and Arriaga, 1985; Stevens and Richmond, 1976; Dittmar et al., 1977; Dittmar and Stevens, 1980; Sanders and Gabriel, 1985) may provide a more complete representation of the extent of the Uvalde Gravel than geological maps. The widespread geographical distribution of these soils suggests that the Uvalde Gravel formerly covered a large portion of the Rio Grande Plains. The Quihi, Hindes, Yologo, and Olmos soils in Medina County appear to represent a sequence of increasing erosional stripping on the Uvalde Gravel. Quihi, Hindes, and Yologo soils are on topographic highs in inverted landscapes where the parent material contained enough chert to armor the surface against erosion, whereas the Olmos soil is on erosional surfaces where armor was absent or stripped away. The Victoria and Mercedes soils mapped on the Kinchloe Prairie in western Medina County (Dittmar et al., 1977) and Montell soils on summit surfaces in Uvalde, Dimmit, and Zavala Counties (Stevens and Richmond, 1976; Stevens and Arriaga, 1985) may have formed in fine-grained facies of the upper Uvalde Gravel.

Late Miocene Oarendonian climates in the Texas Panhandle were probably mild, subhumid, and temperate to subtropical (Schultz, 1990:56). Presence of alligator and large tortoise fossils suggests warm temperatures and mild, frost-free winters (Hibbard, 1960). Large kaolin deposits contained in karst basins near Leakey (Schoch, 1931; Price, 1933:506) provide evidence for a similar, intense mineral weathering regime in the Edwards Plateau. Terra Rossa soils, perhaps similar to the Rumple, Roughcreek, Hensley, Dina, Comfort, Speck, Spires, and Tarpley soils (Table 1) on stable landscape positions today, may have blanketed much of the Edwards Plateau landscape after such a climate.

The Goliad Formation and the Uvalde Gravel were deposited in the Late Miocene and Pliocene (Hoel, 1982; Eargle and Foust, 1962) after Balcones Faulting raised the Edwards Plateau relative to the Coastal Plain (Ragsdale, 1960) and steepened the gradient of streams draining the Edwards Plateau. Steeper stream gradients, landslides and slope failure triggered by earthquakes, and the continuing increase in aridity during Late Pliocene (Hoel, 1982:92) decreased landscape stability and increased the sediment supply to streams draining the Edwards Plateau. Late Hemphillian faunas in the Texas Panhandle suggest progressive aridity during the Late Miocene and Early Pliocene (Schultz, 1990:82). Channels began to erode headward, carving the canyons along the southern margin of the Edwards Plateau. Below the Balcones Escarpment where gradients decreased, streams ceased downcutting and began aggrading. There streams deposited cobbles, pebbles, and calc-lithic sands in braided channels and on alluvial fans.

The orientation of the Uvalde Gravel deposits from eastern Medina County through eastern Frio and western Atascosa Counties into McMullen County (Brown et

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I

, I

I

I I

al., 1983) suggests that the paleo-Medina River was a tributary of the Miocene Mathis fluvial system (Hoel, 1982:26). The Mathis fluvial system was a basin-fringe river which occupied the approximate course of the modern Nueces River from George West to Corpus Christi. It was fed by a single tributary system draining a proximal source in the Edwards Plateau (Hoel, 1982:75). The Mathis fluvial system was a broad, shallow, braided perennial stream consisting of two channels. The primary channel was occupied during normal and low-to-moderate flood flow, and the flood channel was occupied only during high-intensity flood flow. During floods of low to moderate intensity, the flood channel acted as part of the floodplain, accumulating splay sands and silts and floodplain clays. During floods of great magnitude the flood channel accumulated chaotic, channel-fill deposits, including large bars, scour fills, and sheet gravels (Hoel, 1982:45-46). Complex splay deposits covered large areas of the flood channel and the adjacent floodplain (Hoel, 1982:50,55,74). Clayey and loamy strata were probably interbedded with gravelly and cobbly layers. Water-stable aggregates composed of silt and clay behave much like sand in fluvial depositional systems. Muds can be deposited by fast moving water if the clay particles were bound together into sand-size aggregates. Variable discharge in the Mathis fluvial axis reflects aridity and short duration, high intensity rainfall events (Hoel, 1982:72). The Uvalde Gravel in eastern Medina County appears to consist of braided stream deposits similar to the Mathis lobe of the Goliad Formation (Hoel, 1982:45). Some weathering of limestone clasts in the Uvalde Gravel probably occurred as successive layers of alluvium were deposited during the Miocene and Pliocene.

Clay eroded from Terra Rossa soils in the Edwards Plateau was probably the primary source of clayey alluvium in the Uvalde Gravel. Geologic materials eroded from valley walls and cutbanks of channels incised into the Cretaceous Escondido formation were another source. In situ weathering of limestone fragments yielded clayey residue, and volcanic ash and atmospheric dust could have contributed small amounts of clay.

Pleistocene climates of the Edwards Plateau are unknown, but are presumed to have been wetter than the present-day climate. Sea levels during glacial maxima were some 150 m lower, providing more relief and erosive energy in streams below the Balcones Escarpment (Bernard and leBlanc, 1965). As increased vegetative cover effectively stabilized the landscapes, sediment load in streams decreased, aggradation downstream ceased, incision into the unconsolidated Coastal Plains sediments resumed, and landscapes inverted. The petrocalcic horizon of the Quihi soil acted as a caprock to prevent extensive backwearing of the steep western valley wall of the Medina River at Castroville. The river has downcut some 80 m since the deposition of the Uvalde Gravel. Reorganization of the drainage network via stream capture during the Plioene and Pleistocene was extensive (Woodruff and Abbott, 1986).

The parent material of the Quihi soil was poorly-sorted coarse sand and gravel, deposited as bedload in channels by the Mathis fluvial system, with subordinate medium to fine sand, silt, and clay (Hoel, 1982:25-26,36,40-41). The proximity the Edwards Plateau largely explains the abundant chert armor in and on the Quihi soil. At Castroville, the Uvalde Gravel contained more limestone and chert pebbles and cobbles than the distal Goliad Formation, and therefore yielded more chert upon weathering.

MORPHOLOGY AND DIAGNOSTIC FEATURES OF SOIL TAXONOMY

Munsell color and organic carbon content in the A and Bt horizons (0 to 41 cm) meet the requirements of a mollic epipedon (Soil Survey Staff, 1990:5). Mollic colors, mainly on structural surfaces, occupy 25% of the Btss horizon but the dominant matrix colors have chroma greater than defined in the mollic epipedon.

Page 65: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

An argillic horizon is recognized from 8 to 74 cm (Soil Survey Staff, 1990: 11). The increase in clay content from the truncated eluvial A horizon to the Bt is 8.6% (absolute), just adequate to meet the argillic horizon requirement in clayey soils (Soil Survey Staff, 1990:12). However, the clay increase of32.5% (absolute) between the intact eluvial satellite A horizon and the Bt of the argillic horizon suggests great age for this soil and meets the taxonomic requirements for the Pale subgroup. Chert fragments in the A, Bt, and Btss horizons are coated with iIluvial clay but ped surfaces are not. Clay coats on ped surfaces in high shrink-swell clayey horizons either do not form or are destroyed by cyclic volume changes (Nettleton et al., 1969).

Leaching of calcium carbonate from the upper solum probably preceded clay eluviation from the A horizon and reddening of the B horizon (Gile et aI., 1981:72). Atmospheric and organic acids dissolved calcium carbonate to leave a residual concentration of chert, clay, and iron. The rock fragments in horizons above the Btk horizon are composed solely of chert, though a few limestone lithoclasts and exfoliated slabs of caliche are found immediately above the petrocalcic horizon (Table 2). The absence of limestone clasts above "the Btk horizon and the presence of a red clayey argillic horizon indicate a high degree of weathering. The chert pebbles and to a large extent the red clayey argillic horizon above the petrocalcic horizon are thought to be residual weathering products.

The Btk horizon (54 to 74 cm) with 32% calcium carbonate equivalent qualifies as a calcic horizon (Soil Survey Staff, 1990:13). Strongly cemented pendants of secondary carbonates are attached to the lower surfaces of solution-facetted limestone pebbles in this horizon. The caliche of the Bkm horizons (74 to 153 cm) meet the requirements for a petrocalcic horizon (Soil Survey Staff, 1990: 19). These horizons are continuously cemented and completely plugged by secondary carbonates. Although the top 1 cm of the petrocalcic horizon is indurated, a laminar cap does not occur in this particular pedon. A laminar cap does occur, however, in pedons observed in nearby pit walls. The upper surfaces of limestone fragments embedded in the petrocalcic horizon are solution-facetted while the lower surfaces have secondary lime pendants.

Slickensides, a feature of Vertisols and Vertic intergrades (Soil Survey Staff, 1990:28), in the Btss horizon (41 to 54 cm) do not affect the classification of this pedon because cracks during dry periods do not extend to the surface. The grooved and polished surfaces (slickensides) on parallelepipeds (wedge shaped peds) are produced by one mass of soil sliding against another (or a rock fragment) during volume changes associated with wetting and drying. The overlying Bt horizon does not have slickensides because its very high (75%) content of chert pebbles and cobbles form a rigid matrix that constrain soil movement. The lO-fold decrease in rock fragment content of 75 to 7% from the Bt to the Btss is notable. The underlying Btk horizon has a rock fragment content of 65%, but nearly one-half the fragments are limestone. The Btss horizon could have formed from a stratum composed mainly of limestone clasts. An alternative explanation of the low rock fragment content invokes the high shrink-swell potential of the Btss horizon. Shrinking and swelling processes may physically ratchet chert pebbles into the overlying Bt horizon as the soil wets and dries.

CALCIUM CARBONATE IN TIlE QUllII SOIL

The morphology of the Quihi soil reflects a long and complex history. We propose the following sources and processes as a general guide to origin of CaC03 in the Quihi soils. Dissolution, translocation, and reprecipitation of calcium carbonate were the major weathering processes in the Quihi soil. Some of the processes occurred

I

Page 66: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

\

simultaneously, and because the parent material was an aggrading fluvial deposit, the results of these processes were welded one on top of another.

Potential sources of non-pedogenic carbonate in the Quihi soil are the parent material, atmospheric wetfall and dryfall, floodwater, and groundwater. Atmospheric sources likely contributed some carbonate to the Quihi soil, but in the Edwards Plateau dustfall as a source of carbonate is probably not important today (Rabenhorst and Wilding, 1986). Certainly, dustfall is not required to explain the accumulation of secondary carbonates in the Quihi soil, given the abundant carbonates in the parent material sediments, groundwater, streamflow, and floodwater. While calcareous dust is not necessary to form a petrocalcic horizon, it may plug a layer in a short time because it is so reactive.

Floodwater is a source of carbonate in aggrading fluvial systems such as alluvial fans and floodplains. Water-borne carbonates provide a mechanism for recalcification of argillic horizons on floodplains and alluvial fans (Mandel, personal communication, 1990). Calcium bicarbonate-saturated floodwater percolating through the soil may react with acids derived from organic matter and soil atmosphere and thereby become unsaturated with respect to calcite.

Carbonate chemistry in soils is complex. Calcite solubility in pure water varies directly with temperature. However, calcite solubility in C02-charged water varies inversely with temperature because C02 solubility, which largely regulates calcite solubility, also varies inversely with temperature. Rainfall, unsaturated with respect to calcite, usually has a lower temperature than the surface soil. As rainwater warms upon entering the soil, both C~ concentration and calcite saturation point decrease. But, warm temperature and moist soil favor microbial respiration, resulting in higher soil atmosphere C~ concentration and carbonate solubility. The C02 content of the soil air is about 6 to 10 times higher than that of the atmosphere (Baver, 1965:205). Organic acids, also originating from microbial respiration, further increase carbonate solubility in soil water.

Dissolution and reprecipitation of limestone clasts have totally or partially cemented the Uvalde Gravel to depths up to 6 m. Fragmental layers near the surface were plugged with ilIuvial carbonates. The degree of cementation and plugging decreases with depth, but some pedogenesis is evident throughout the section. This suggests that weathering occurred simultaneous with aggradation during the Miocene and Pliocene, and during the Pleistocene after aggradation ceased.

Solution facets on limestone pebbles are attributed to the dissolution of the upper surface of initially subrounded clasts by soil water, with subsequent deposition of carbonate pendants on the lower surface (Bryan, 1929; Bretz and Horberg, 1949). Downward moving soil water preferentially dissolves the upper surface of a limestone fragment because the upper surface is wet more frequently. In addition, soil water that contacts the upper surface has less dissolved calcite than water contacting the lateral and lower surfaces. In fact, the lower surtace is exposed to soil water saturated with calcite dissolved from the upper surface. The lower surfaces of limestone clasts in fragmental layers sometimes have abundant calcite crystals which suggest that water clings to, slowly evaporates from, and carbonates precipitate there. The net result is a loss of carbonate from the upper surface and a gain on the lower surface (Figure 3).

Solution-facetted limestone fragments appear to be characteristic of calcretes developed in gravelly limestone parent materials. We have observed them in petrocalcic horizons at several locations in the Rio Grande Plains, Edwards Plateau, and Trans-Pecos of Texas. McFadden et al., (1991:26) and Sowers et al., (1988) reported they occur well below the soil surface in fans and terraces of Kyle Canyon in southern Nevada.

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1

I II III

Figure 3. Schematic Oiagr •• 01 Solution Facettlng and Pend.nt Formation on a Limestone Fragment.

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CALCIC AND PETROCALCIC HORIZONS Several hypotheses exist about the mechanisms involved in the accumulation of

calcium carbonate in soils. Woolnough (1928) and Price (1933) described a process of carbonate accumulation relative to soil horizons or "zones", as they called them. The following is quoted from Price (1933:510-511).

• ... the circulation of ground waters in areas of seasonal precipitation effects the downward movement of saturated solutions... Evapo-transpiration would seem to be the controlling factor in the precipitation of caliche, since it produces the upward rise of the soil solutions during the dry seasons... The chief place of precipitation of caliche is the B zone of the soil, the A horizon in some places being wanting or inconspicuous. The B zone constantl y invades the C zone to the depth of ground-water activity. Some mineral deposition occurs in the C zone as long as the base is above the water table. The direction of movement of the precipitating solutions is circulatory, both up and down. The main body of the material may be originally deposited during the local rise of solutions, but aided by gradual erosion of the overlying soil, the deposits are forced deeper and deeper into it by downward leaching (re­solution) and re-deposition .•

Water movement described by Price and Woolnough probably occurs only in materials fine enough to promote significant capillary rise of water. In fragmental materials, water movement is downward until the large pores became plugged with carbonates. The development of plugged and laminar horizons known as petrocalcic horizons as described by Gile et al.( 1981) is quoted below.

·With continued carbonate accumulation, most or all pores and other openings in the soils become filled by carbonate: primary grains have been forced apart; bulk density has increased; and infiltration rate has markedly decreased. This process results in the plugged horizon, which develops in the last part of stage III.

After development of the plugged horizon, the laminar horizon forms on top of it. Differences between the laminar and plugged horizons are so great that the fabrics differ in kind. The laminar horizon has much more carbonate than the plugged horizon and essentially no allogenic skeletal grains. Rather than the carbonate being a filling between skeletal grains, it occupies almost the entire horizon and the skeletal grains are incidental. The laminar horizon is a new soil horizon in the sense that it consists almost entirely of authigenic material and hence thickens the soil by its own thickness. The overlying horizons must have been displaced upward from their original position" (Gile et al., 1981:67).

We believe that evapo-transpiration is necessary to form and maintain petrocalcic horizons in South Texas. Figure 4 is a schematic model that illustrates the carbonate compartments and movements involved in the formation of petrocalcic horizon. The balance between deep drainage (E) and evapo-transpiration (F, I, I) probably determines whether petrocalcic horizons (1) develop proanisotropically, (2) remain stable, or (3) degrade. We propose this model to explain the formation of petrocalcic horizons in unconsolidated, carbonatic parent materials in the Edwards Plateau, Rio Grande Plains, and Trans-Pecos areas of Texas. Examples of these materials are marl beds in the Boquillas, Buda, Fort Lancaster, Fort Terrett, and Glen Rose Formations in

Page 69: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

ATMOSPHERE

SOIL 1 ~- A BI tG HORIZON 1

I ,

t 1

- -~ -- ----.-A, Bt C 1 ..

- "' --- 1 [,

· :0 J ...... '. · I .. / I' "- __ 1 - ,

-- ~.-.... Bkm ..

-~ :+ ~.". : ! F · - / '~-- 1 1 -

'I 1----.-Bk _.

-- -~ 1 1

EI , ,

Plant Solid phase Aqueous phase Soil atmos phere

Figure 4. D.agram of a Compartment and Transfer Model for Petroeale.e Honzon Formation in South Texas, Sea Text for Explanat.on.

Page 70: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

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I )

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the Edwards Plateau, and alluvium (including the Uvalde Gravel and Goliad Formation) derived from the Edwards Plateau.

Infiltrating rainwater (B) dissolves solid carbonates (C) in the A and Bt horizons and trans locates aqueous carbonates (D) into the Bkm and Bk horizon through fractures in the laminar cap. Dustfall (A) probably is not an important source of carbonates in the Edwards Plateau today (Rabenhorst and Wilding 1986). Rainfall events that exceed the water holding capacity of the profile fill it, and the gravitational water that drains (E) from the Bk horizon removes some of aqueous carbonates from the soil. Aqueous carbonates in the capillary water held by the Bkm and Bk horizons equilibrate (C) with temperature and C~ regime. Aqueous carbonates precipitate (C) to the solid phase when evaporation (G) or transpiration (H) withdraw water from the horizon or when C02 content or pH drop. Capillary water in the Bk and Bkm horizons moves upward (F) in response to a water potential gradient created by evaporation and plant root suction. Woody plants can transpire large amounts of water from the soil in warm climates. Roots commonly mat on the upper surface (laminar cap) and in fractures of the petrocalcic horiwn. Water enters the roots (1) to be transpired (H) through the leaves, concentrating CaC03 around roots on the laminar cap and in fractures to leave a precipitate (I) of CaCOJ.

The formation of a laminar cap may require warm season precipitation. In South Texas most of the annual rainfall, plant growth, and evapo-transpiration occur during the warmer months. Small storms wet the uppermost part of the petrocalcic horizon (indurated laminar cap) most frequently. Wetting front penetration associated with larger storms into the strongly and weakly cemented horizons is less frequent. The strength of cementation may be directly related to the frequency of dissolution and precipitation.

Figure 5 illustrates the stages in the development of the Quihi soil in the Uvalde Gravel. Stage 1 shows the removal of carbonates from the upper column and the accumulation of secondary carbonates as pendants on the lower surface of rock fragments. Stage II portrays truncation of the surface layer and subsidence resulting from the dissolution of limestone fragments and the loss to deep drainage and the plugging of fragmental layers with secondary carbonates. Further subsidence and truncation, residual concentration of chert and clay in the upper solum, clay illuviation and development of an argillic horizon, and plugging of skeletal layers occur in Stage III. Stage IV illustrates complete stripping of the non-gravelly surface, subsidence, and residual concentration of clay and chert in the upper solum, complete plugging of skeletal strata, and cementation of the petrocalcic horizon and formation of a laminar cap. Stage V is the present Quihi soil, depicting the loss of carbonates above the petrocalcic horizon and degradation of the laminar cap. The mantle of chert fragments protects the Quihi soil against more extensive erosion.

DEGRADATION OF TIlE QUIHI PETROCALCIC HORIZON

The Uvalde Gravel and Goliad Formation were partially plugged and cemented with secondary carbonates during aggradation. Weathering during the Pleistocene finished plugging the material. As Early Holocene climates became more arid, carbonates precipitating from the soil solution withdrawn by roots matted on the upper surface of the Bkm horiwn. The solution-facetted limestone pebbles near the top of -the petrocalcic horizon suggest that degradation processes balance or exceed formation in the present climate. The laminar cap of the petrocalcic horizon would engul f and encase the limestone fragments if proanisotropic processes were dominant. The continuous petrocalcic horiwns in Olmos soils on nearby Holocene age erosional

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Bw2 toW .ai1J.llbl A

Bki

Bk2

Bk3

BkS

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figure 5. Sequence of Quihl Soil for.atlOn In the Uvalde Gravel. Carbonate accumulations are indicated bV black forms, li.estone fragments are white, chert fragments are grav, and strata of fine earth and vOids in fragmental strata are white.

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surfaces suggest that formation and degradation processes can occur simultaneously. Petrocalcic horizons are best preserved on stable geomorphic surfaces in arid

climates where proanisotropic processes (formation) are more effective than proisolropic processes (degradation). The absence ofpetrocalcic horizons In soils with wet ustic moisture regimes (Price, 1933:513-514) suggests that degradation exceeds formation in moist sub-humid climates. Exfoliation is probably a major degradation process in petrocalcic horizons lacking clastic fragments. Competent rock fragments strengthen the calcrete and retard exfoliation. Price (1933:514) observed that gravelly caliches persist longer in subhumid climates than clayey caliches.

Figure 6 illustrates a degrading petrocalcic horizon in an Olmos soil described near George West. Roots of woody plants pry masses of cemented caliche away from the main body of the petrocalcic horizon. Many soils with petrocalcic horizons in the Edwards Plateau and Rio Grande Plains are skeletal (contain <35% rock fragments) because of detached caliche fragments. InfIltrating rainwater dissolves these exfoliated caliche fragments and translocates aqueous carbonates into the Bkm horizon through fractures in the laminar cap. After plants have exploited the readily available moisture in the A horizon, roots matted on the laminar cap and fractures within the Bkm horizon begin to extract stored water. Aqueous carbonates precipitate near the site of water extraction. The laminar accumulations on upper and lower fracture surfaces suggest that detached fragments are a source of water for plants, and a source of aqueous carbonate for precipitation.

AGE OF TIlE PETROCALCIC HORIZON

The apparent radiocarbon age profile of a pelrocalcic horizon may be an artifact of the C~ content at the site of carbonate precipitation. Carbonates near the interface with the soil atmosphere precipitate in the presence of an elevated carbon dioxide content, whereas one to two m below the laminar cap carbonates precipitate in an atmosphere rarefied in C~ because respiration is low. Extensive dissolution of petrocalcic horizons on the Edwards Plateau should be expected after the abnormall y wet winter of 1991-1992. If atmospheric C~ diffuses through the laminar cap, the radiocarbonate clock would be reset to zero as aqueous carbonates precipitate.

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SOIL HORIZON

A

Bkm

Figure 6. [Ilustration of a Degrading Petroealele Horizon In an Olmos 5011 near George West, Texas. The petroealele horizon and detaehed eal iehe fragments are white, and fine earth IS black. I

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ACKNOWLEDGMENTS

The authors acknowledge Mr. Glenford Boehme for permission to study this soil on his farm. The staff of the National Soil Survey Laboratory provided timely results of determinations. Thanks go to Mr. Ervin Willard, Area Conservationist, for supporting our effort on this project. Dr. C.T. Hallmark, Dr. Dennis Nettleton, Dr. Doug Wysocki, Dick Base, Bob Ahrens, Gaylon Lane, Charles Batte, Micki Yoder, and C.L. Girdner reviewed the manuscript and provided constructive criticism. Any errors in interpretation remain the responsibility of the authors.

REFERENCES CITED

Baver, L.D. 1965 Soil Physics. 3rd. Ed. John Wiley and Sons, Inc. New York.

Bennett, R.R., and A.N. Sayre 1962 Geology and ground-water resources 0/ Kinney County, Texas. Texas Water

Commission Bulletin 6216.

Bernard, H.A., and R.I. leBlanc 1965 Resume of the Quaternary geology of the northwest Gulf of Mexico province.

In: H.E. Wright and D.B. Frey (eds.), The Quaternary o/the United States. Princeton University Press, Princeton, New Jersey.

Bretz,1. Harlen, and Leland Horberg 1949 Caliche in southeastern New Mexico. Journalo/Geology 57(5):491-511.

Brewton, Joseph L., Frith Owens, Saul Aronow, and VlTgii E. Barnes 1976 Geologic Atlas o/Texas, Laredo sheet. Map (scale 1:250,(00) and legend.

University of Texas Bureau of Economic Geology, Austin.

Brown, T.E., Noel B. Waechter, Frith Owens, Ike Howeth, and Virgil E. Barnes 1976 Geologic Atlas 0/ Texas, Crystal City-Eagle Pass sheet. Map (scale

1:250,0(0) and legend. University of Texas Bureau of Economic Geology, Austin.

Brown, T.E., Noel B. Waechter, Peter R. Rose, and Virgil E. Barnes 1983 Geologic atlas 0/ Texas, San Antonio sheet. Map (scale 1:250,000) and

legend. University of Texas Bureau of Economic Geology, Austin.

Bryan, Kirk C. 1929 Solution facetted limestone pebbles. American Journal a/Science 18:193-208.

Byrd, C.L. 1971 Origin and history of the Uvalde Gravel of Central Texas. Baylor Geological

Studies Bulletin 20.

Deussen, Alexander 1924 Geology o/the Coastal Plain o/Texas West 0/ Brazos River. U.S. Geological

Survey Professional Paper 126.

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Dittmar, Glenn W., Michael J. Deike, and Davie L. Richmond 1977 Soil survey of Medina Q]unty. Texas. USDA Soil Conservation Service and

Texas Agriculture Experiment Station. 82 pp. + 58 pI.

Dittmar, Glenn W., and Jack W. Stevens 1980 Soil survey of Atascosa County. Texas. USDA Soil Conservation Service and

Texas Agriculture Experiment Station. 131 pp. + 67 pI.

Eargle, D.H., and R.T. Foust, Jr. 1962 Tertiary stratigraphy and Uranium mines of the Southwest Texas Coastal Plain,

Houston to San Antonio, via Goliad. In: Rainwater, E.H. and R.P. Zingula (eds.), Geology of the Gulf Coast and Central Texas and Guidebook of Excursions. pp. 225-253 Houston Geological Society 1962 Annual Meeting of the Geological Society of America and Associated Societies, Houston.

Gile, Leland H., John W. Hawley, and Robert B. Grossman 1981 Soils and geomorphology in the basin and range area of southern New

Mexico. New Mexico Bureau of Mines and Mineral Resources Memoir 39.

Gustavson, T. C. 1990 Geologic Framework and Regional Hydrology: Upper Cenowic Blackwater

Draw and Ogallala Fonnations. Great Plains. University of Texas Bureau of Economic Geology Special Publication.

Hibbard, C. W. 1960 An interpretation of Pliocene and Pleistocene climates in North America, the

President's Address: Michigan Academy of Science, Am, and Letters, RePOI1 for 1959-1960, p. 5-30.

Hill, Robert T. 1891 Notes on the Geology of the Southwest. American Geologist, 7:254-255,

366-370.

Hoel, Holly A. 1982 Goliad Formation of the South Texas Gulf Coastal Plain: Regional Genetic

Stratigraphy and Uranium Mineralization. Unpublished Master's thesis, University of Texas at Austin.

McFadden, L.D., Ronald G. Amundson, and Oliver A. Chadwick 1991 Numerical modeling, chemical, and isotopic studies of carbonate accumulation

in soils of arid regions. In W.D. Nettleton (ed.) Occurrence, Characteristics, and Genesis of Carbonate, Gypsum, and Silica Accumulations in Soils, pp. 17-35. Soil Science society of America Special Publication 26.

Nettleton, W.D., K.W. Flach, and B.R. Brasher 1969 Argillic horizons with clay skins. Soil Science Society of America

Proceedings, 33(1):121-125.

Plummer, EB. 1933 Cenozoic systems in Texas. In E.H. Sellards, W.S. Adkins, and EB.

Plummer (eds.), The Geology of Texas, v. 1. Stratigraphy, pp. 519-818. University of Texas Bureau of Economic Geology Bulletin 3232.

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Price,VV.Armstrong 1933 Reynosa problem of South Texas, and origin of caliche. Bulletin of the

American Association of Petroleum Geologists, 17(5):488-522.

Rabenhorst, Martin C., and Lawrence P. VViiding 1986 Pedogenesis on the Edwards Plateau, Texas: 1. Nature and continuity of parent

material. Soil Science Society of America Journal, 50(3):678-687.

Ragsdale, I.A. 1960 Petrology of Miocene Oakville Formation, Texas Coastal Plain. Unpublished

Master's thesis, University of Texas at Austin.

Ramsey, Robert N., and Norman P. Bade 1977 Soil survey of Guadalupe County, Texas. USDA Soil Conservation Service

and Texas Agriculture Experiment Station. 82 pp + 58 pI.

Sanders, Russell R., and VVayne I. Gabriel 1985 Soil survey of Webb County. Texas. USDA Soil Conservation Service and

Texas Agriculture Experiment Station. 145 pp + 102 pI.

Schoch, E.P. 1931 The kaolin deposits of section 71, block 3, TVVNGRR Survey, 5 miles

northwest of Leakey, Real County, Texas. University of Texas Bulletin. 3120:140-161.

Schultz, Gerald E. 1990 Clarendon ian and Hemphillian vertebrate faunas from the Ogallala Formation

(Late Miocene-Early Pliocene) of the Texas Panhandle and adjacent Oklahoma. In T.C. Gustavson (ed.), Geologic Framework and Regional Hydrology: Upper Cenowic Blackwater Draw and Ogallala Fonnations. Great Plains. pp. 56-97. University of Texas Bureau of Economic Geology Special Publication.

Soil Survey Staff 1990 Keys to Soil Taxonomy, fourth edition. SMSS Technical Monograph No.6.

Blacksburg, Virginia.

Sowers, Ianet M., Marith C. Reheis, E.M. Taylor, and Jennifer VV. Harden 1988 Geomorphology and pedology on the Kyle Canyon Fan, Southern Nevada: II.

Soil development as a function of time. In D.L. VVeide and M.L.Faber (eds.), Field trip guidebook, pp. 142-146. University of Nevada-Las Vegas Special Publication 2.

Stevens, lack VV., and Davie L. Richmond 1976 Soil survey of Uvalde County, Texas. USDA Soil Conservation Service and

Texas Agriculture Experiment Station. 10 1 pp + 83 pI.

Stevens, lack VV. and Dan Arriaga. 1985. Soil Survey of Dimmit and Zavala Counties. USDA Soil Conservation Service and Texas Agriculture Experiment Station. 161 pp + 136 pI.

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Thornthwaite, C.w. 1931 The climates of North America; according to a new classification.

Geographical Review 21 :633-655.

Trowbridge, A.C. 1932 Teniary arul Quaternary Geology o/the Lower Rio Grarule Region. Texas.

U.S. Geological Survey Bulletin 837.

Van Wambeke, A., P. Hastings, and M. Tolomeo 1986. Newhall Simulation Model: A BASIC program for the IBM PC. Department

of Agronomy, Cornell University, Ithica, New York.

Woodruff, Charles M., and Patrick L. Abbott 1986 Stream piracy and evolution of the Edwards Aquifer along the Balcones

Escarpment, Central Texas. In Patrick L. Abbott and Charles M. Woodruff (eds.), The Balcones Escarpment: Geology. Hydrology. Ecology. and Social DevelOl!ment in Central Texas, pp. 77-89. Comet Reproduction Service, Santa Fe Springs, Ca.

Woolnough, W. G . 1928 Origin of white clays and bauxite, and chemical criteria of peneplanation.

Economic Geology 23:887-894.

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THE CLIMATE OF THE INNER GULF COASTAL PLAIN OF SOUTH CENTRAL TEXAS

George W. Bomar Weather & Dimate Specialist

Texas Water Commission

INTRODUCTION The climate of the Inner Gulf Coastal Plain (IGCP) of South Central Texas is humid

subtropical, characterized by mild winters and very warm, muggy summers. The area experiences frequent intrusions of polar air in the 6-month period beginning in October and ending in March; however, cold spells are almost always short-lived. With the approach of the summer solstice, the upper-atmospheric westerlies migrate northward out of the central U. S., leaving the Texas coastal plain to be dominated by the vast subtropical ridge of high pressure that drifts northward out of the tropics and holds forth for nearly all of the late spring, summer, and early autumn. Fronts seldom penetrate the region, and an almost incessant stream of southerly winds from the Gulf of Mexico ensures a climate of mild to warm nights and very warm to hot days.

THE DISTRIBUTION OF PRECIPITATION The continual exchange of airmasses from land to sea and from sea to land gives rise to

clouds, some of which engender appreciable rainfall in the Texas coastal plain. But the interaction of polar and Arctic airmasses with tropical flow is highly erratic, so the patterns of precipitation that characterize the climate of the Inner Gulf Coastal Plain from year to year vary dramatically.

Areal and Seasonal Variability of Rainfall The distribution of precipitation in the inner coastal plain is a function of proximity to the

Gulf of Mexico, the source of the bulk of atmospheric moisture entering the state. Thus, in an average year, annual precipitation varies appreciably from east to west within the Inner Gulf Coastal Plain. Mean annual precipitation is heaviest in the vicinities of laGrange (37.52 inches) and Flatonia (37.41) and least in the extreme western sector, at Crystal City (21.34) and Uvalde (24.10). Mean annual precipitation at other key points within the IGCP: Pearsall (24.54), San Antonio (29.13), Floresville (29.58), Austin (31.50), and Gonzales (33.15).

The IGCP is one of two areas in Texas where sharp gradients in mean annual precipitation occur due to the influence of marked changes in topography. Isohyets (or lines of equal amounts of precipitation) on a map depicting mean annual precipitation (Fig. 1) bend sharply to the west along the Balcones &carpment, or at the foot of the Texas Hill Country. The uplift of moist Gulf air by the rather abrupt relief features of this area is responsible for some points in the vicinity of the &carpment traditionally garnering more rainfall in a year (24 to 28 inches) as the lower Texas coast.

Rainfall in the IGCP is rarely spread uniformly throughout the year. The region has its customary wet and dry seasons. Some periods, like the latter half of spring and the early autumn, furnish the bulk of annual rainfall, while others, like the winter and summer, provide appreciably lesser amounts of rain. The late summer and early autumn period can be the wettest of the year, if one or more prolific rain-making tropical cyclones choose the Lone Star State to be their point of landfall.

Because of the contribution of tropical weather disturbances, September is normally the wettest month of the year in central and eastern portions of the region; May is only slightly less wet. In the westernmost sector (Uvalde and Zavala Counties) May is about one-quarter inch wetter than September. March, on the other hand, is either the driest or next-to-the driest month of the year in all of the region. In the east, July customarily is the stingiest month for rainfall, while in the central and western portions, December and January vie for the distinction as the driest months.

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Figure 1. Mean annual precipitation (inches)

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Precipitation over the whole of any year varies widely from year to year. Drought years alternate with wet years, though the pattern is highly erratic. Some years furnish as little as 18-25 inches of rain, while others provide in excess of 40 or 45 inches. Phenomena such as El Nino undoubtedly influence the character of the rainfall distribution in some years. The year of 1991 was exceedingly wet in the IGCP, for instance, because of the evolution of an intense episode of El Nino in the central tropical Pacific Ocean. The inordinate warming of surface waters near the Equator intensified the subtropical jet stream--the flow of moisture-laden winds in the upper atmosphere--which passes over Texas. An almost incessant flow of moist Pacific air, combined with low-level inflow of moist air from the Gulf of Mexico, into Texas during the winter of 1991-92 produced epic flooding on rivers and streams cutting through the IGCP. The winter proved to be the wettest cold season of the century, and in some places, the wettest winter since at least the Civil War. In fact, with 50-60 inches of rain having been measured in parts of the region during 1991, the winter capped the year as the second wettest of any season in recorded weather history.

Role of the Thunderstorm as Rainmaker Though the prodigy of many thunderstorms in Texas are loathsome, parts of the IGCP might revert to a semi-arid steppe climate (like that of the Trans-Pecos region of Texas) without the plenteous rainfall generated by the towering thundercloud. Too often the bitter (hail, damaging winds, lightning, even tornadoes) must be tolerated in order to gain the sweet (rains of 2 to 4 inches). In the relatively warm and humid subtropical air that frequently envelops South Central Texas, two species of thunderstorms materialize as major producers of rainfall: the airmass thunderstorm, and the frontal thunderstorm.

The airmass variety of thunderstorm forms far from cold fronts and stems from the differential heating of the land surface that sets a vigorous updraft in motion. They are most numerous in summertime, and almost all of them crop up in daytime but perish before or not long after nightfall. Occasionally, an airmass thunderstorm will yield a substantial amount of rainfall, one inch or more, in a fraction of an hour. Most of them, however, generate only modest rainwater.

While the airmass thunderstorm is generally short-lived and seldom produces destructive wind or hail, its cousin--the severe, frontally-induced storm--spawns quickly, persists for comparatively long time periods, and often metes out large amounts of rainfall. Not infrequently, some of the frontally-induced storms align themselves in the form of squall lines, which deliver strong, chilling winds along with slashing rains. In the spring and early summer in South Central Texas, multicell storms are triggered by approaching cold fronts, and rainfall can be torrential (3 to 5 inches) in only a few hours. The sumptuous rains so prevalent in spring come from these frontal, multicell thunderstorms.

Excessive Rainfall and Flooding As in most other areas of Texas, the IGCP is susceptible to rainwater in quantities and in

time intervals too exaggerated for the land surface to accommodate. Because virtually all of the coastal plain's precipitation is some form of rainfall (snowfall occurs only once every 4-6 years and is rarely substantive), the impact of excessive rains on the flow of water in rivers and streams is prompt. Runoff peaks on most rivers in late spring or early summer, concurrent with or immediately after the typically bountiful rains of April, May, and June. Peak runoff in the coastal plain may occur in late summer or early autumn, however, if a tropical storm or hurricane impacts the Texas coastline.

Runoff occasionally becomes unmanageable in South Central Texas, and the destructive floods that ensue can exact a toll in lives lost and property damages sustained. This is especially true in the upland portions of the coastal plain--along and above the Balcones Escarpment--where rapidly flowing waterways cut sharply through the Hill Country. Major floods can occur in every season, but spring is most favored because it usually marks the end of the period of soil-moisture accumulation.

1\vo kinds of storm events are the instigators of the most common floods that occur in Texas. One is the general, prolonged episode of heavy rain that, through the sheer quantity of

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water unleashed slowly over many hours, creates widespread lowland flooding within a watershed. The easternmost portion of the IGCP is particularly vulnerable to this type of flood, since several broad streams course through this region and rainfall is sometimes more than plentiful. The other is the infamous flash flood, which erupts suddenly from a cloudburst that may send torrents of rainwater upon merely a few square miles of land surface. If that volume of rainwater had been spread out over a vast watershed, little or no flooding would have resulted. But because the rainwater was concentrated in a highly localized basin, rapid peaking of streamflow is just as quickly followed by a rapid recession of the flow.

The northern periphery of the IGCP--or the easternmost precipice of the Hill Country--is most notorious for featuring this type of storm event. The topographic anomaly known as the Balcones Escarpment is cut in hundreds of places by rivers, streams, creeks, and arroyos that fill rapidly when appreciable rains fall upstream on their watersheds. These narrow waterways normally overflow in a matter of minutes, and the water that races through them carries a deadly cargo of uprooted trees, displaced boulders, mud and other debris, and smashed structures. Indeed, the Hill Country's eastern slope is regarded as one of the three most "flash-flood prone" regions in the U. S.

Recurrence of Drought Even in a rain-rich region like the IGCP, Nature can-and occasionally does--shut down its

rainmaking apparatus just as readily as it may activate it. Yet, unlike uncommon wetness, drought is a phenomenon that IS comparatively slow to materialize. It obviously begins once the rains end, but its progression upon the landscape is gradual and hardly recognized until crops begin to wither and water levels in reservoirs and wells dip to precipitous levels. By the time the reality of drought is fully appreciated, its repercussions on agriculture, hydrology, and other sectors of the IGCP economy have already become pronounced. At that point, humanity'S utter helplessness in the face of such a scourge becomes all too evident.

Because the western portion of the IGCP is promimate to the Rio Grande and the Chihuahuan Desert that lies beyond, the region--and particularly the area west of San Antonio-­will undergo periods of prolonged, diminished rainfall. That great desert continually expands and contracts in response to the migration and behavior of the vast, subtropical ridge of high pressure that girds the subtropics for much of the year. The size and strength of that prominent feature of the northern hemispheric atmospheric circulation pattern is, in tum, dependent upon both terrestrial (sea surface fluctuations and volcanic eruptions) and extraterrestrial (solar phenomena) influences.

Though it does not experience drought as often as parts of Texas farther west, the rGCP does sustain prolonged periods of subnormal rainfall that are erratic and stressful. Rainfall deficiencies may occur in the colder half of the year, when intrusions of bone-dry polar air are frequent and the return flow of moist Gulf air above the shallow polar airmass is barely appreciable. Usually, however, the spring quashes the incipient drought ushered in by winter with frequent heavy rains. Summer drought invariably work a greater hardship on the region, because they erupt more rapidly, last longer, and coupled with the intense heat around and after the summer solstice, are more intense. Whether the IGCP will endure drought in the warmer half of the year depends largely on the positioning of the vast subtropical ridge over the southern U. S. and whether the tropics furnish rain-making disturbances.

Every decade of the twentieth century has been spared a drought of some significant magnitude in South Central Texas. Unequivocally, the most calamitous drought of the modem era was the extreme drought that tortured the whole state for nearly all of the decade of the 1950s. That drought is commonly regarded as the benchmark against which all other, past and future, droughts are compared. The Dust Bowl drought, While more severe in areas of the Great Plains to the north of Texas, was only a "moderate" one in the IGCP and other for the latter few months of 1933. Other notable droughts, though of shorter duration, besieged the region in the 191Os, the 1960s, and the 1980s. The worst droughts, in both intensity and duration, have occurred spasmodically, at irregular intervals, and hence are not apparently tied directly to the somewhat predictable sunspot phenonemon.

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THE DIVERSITY OF TEMPERATURE The Inner Gulf Coastal Plain's subtropical latitude ensures that a relatively substantial

amount of solar radiation impinges upon the atmosphere and land surface at steep angles, thereby producing mild to warm temperatures in all but portions of the winter season. Yet, its position on the equatorward side of the mid-latitudes is but one of the controlling factors of the diurnal and seasonal temperature distribution that makes the region's climate highly diverse. The Gulf of Mexico is highly influential as well, serving as the source region for prevailing winds that blow from sea to land with varying amounts of heat and humidity.

Areal and Seasonal Variability of Temperatures While other regions of Texas may succumb to lengthy spells of near or subfreezing

temperatures in winter, the coastal plain rarely experiences frigid spells lasting more than a few days. The intrusion of cold polar, even Arctic, air is rapidly moderated by the warming effect of Gulf waters once the wind veers from the north back into the southeast. In mid-winter, temperatures in the IGCP normally bottom out in the mid or upper 30s, while afternoon readings peak in the low 60s.

Diurnal (night to day) temperature fluctuations are most constant during summer, when Canadian airmasses fail to penetrate Texas, and the region is engulfed by a nearly incessant flow of warm, moist Gulf air. Morning minimum temperatures, and afternoon maximum readings, may vary from day to day only a few degrees over many weeks during the summer. Typical mid­summer temperatures region wide vary from morning lows in the low and mid 70s to afternoon high readings in the 90s.

Temperatures in both spring and autumn often vary markedly from day to day across the region. The abrupt replacement of cold polar with very dry desert air from northern Mexico in late winter or early spring can force daytime maximum temperatures at a given point to increase by 20F to 30F on consecutive days. The arid air exacerbates radiational cooling at night, such that in some areas in the western sector of the IGCP, temperatures can plunge 50F or more in little more than twelve hours, or from mid-afternoon until dawn of the following day. Severe outbreaks of cold air, popularly called "northers," can bring a freeze to more inland locales the morning after temperatures the previous day soared into the 70s and 80s.

Impact of Air-Mass Movements The sudden, drastic gyrations in temperature, wind, cloud cover, humidity, and

precipitation that flavor the climate of South Central Texas would be much more subdued in the absence of the migration-and confrontation--of various kinds of airmasses into the State. Most of the airmasses that influence the state's weather originate to the north or south and enter the state with varying amounts of vigor, depending upon the season of the year and, more especially, the orientation of prevailing air currents aloft over the U. S.

Cold fronts--which mark the leading edge of Canadian and North Pacific airmasses--are responsible for much of the inclement weather that occurs in Texas in every season but summer. The kinds of weather produced by these southward (and southeastward) moving airmasses depends on the stability and moisture content of the incoming airmass and, especially., that of the airmass (usually tropical) being supplanted.

In the coolest four months of the year (November-February), most cold fronts traverse the IGCP rapidly without generating much precipitation at the time of passage. The frequency of frontal movement in these months is so high that southerly (return) flow from the Gulf of Mexico prior to the arrival of the front is often unable to provide the atmosphere over the IGCP with enough moisture for meaningful rainfall to occur. About six cold fronts penetrate the region in each of the coolest months; the average number is less in the months of late spring and in the early autumn.

The movement of warm, moist air through the region from the south usually produces weather events that are more subtle than those that accompany the passage of cold fronts. Outbreaks of heavy or severe thunderstorms often occur--even in the coolest portion of the year-­with cold fronts, and stormy weather is quickly supplanted by sunny skies and drying winds.

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With warm fronts, however, skies are slower to cloud over (and ultimately to clear up), and fog is a frequent signature of the nearness of a warm frontal boundary.

Many of the heavy-rain episodes that come to Texas are triggered by stationary fronts. An incoming cold front may stall, and moist air converging in the vicinity of this frontal boundary can feed budding thunderstorms that may persist for several hours. Fronts are most prone to stagnate in the heart of Texas in the late spring and again in early autumn. A primary reason for May being ) the wettest--or next-to-wettest--month in the region is because of the proliferation of clusters of I slow-moving and rain-rich thunderstorms in the neighborhood of cold fronts that did not have the push to completely penetrate the state.

In winter, long spells of inclement weather in the region recur because a cold front penetrated the state but then stalled in the western Gulf. Copious amounts of Gulf moisture pours over the very shallow, leading edge of the cold airmass, creating widespread thick fog and rain that may persist for up to a week in duration.

Significant weather occasionally develops in the absence of any well-defined frontal systems. Thunderstorms outbreaks or long spells of light rain and thick cloud cover may be due to the influence of "upper atmospheric" weather disturbances that appear to have no relation to any identifiable surface system such as a front or windshift line. Meteorologists commonly refer to these systems high in the atmosphere as "upper-air low pressure areas." Every few weeks in spring, summer, or autumn, one of these "cut-off" lows (so-called because they have been severed from the main mid-latitude flow of air in the upper atmosphere) will migrate eastward (or westward in summer) to trigger showers and thunderstorms. These upper-air lows most often consist of pockets of quite cold air at the 15,000 to 20,000-foot level that drift out of the Rocky Mountain region and destabilize the atmosphere over South Central Texas just enough to promote a rain event.

Virtually all of the severe-weather outbreaks (including snowstorms) that afflict the region in all but the summer stem from the influence of the "jet stream." This broad and potent stream of winds at altitudes where jet aircraft routinely fly (25,000 to 35,000 feet) is the driving force behind much of the weather experienced in Texas each year. The jet stream shoves frigid polar and Arctic air into the region in winter, while concurrently pulling in torrents of moisture from the Pacific and Gulf of Mexico to cause a persistent--but most often Iight--cold rain. It is the root cause of the springtime eruptions of tornado-bearing and hail-producing severe thunderstorms.

Extremes: Heat Waves and Arctic Outbreaks The jet stream manages to seize and deliver to the IGCP one or more batches of Arctic air

each winter, thereby producing the notorious "cold snap." The vast pile of unusually cold air gushes southward, enveloping the whole region for a few days, most often in December or January. Temperatures plunge well below freezing in the mornings, and may remain in the 30s or 40s during the daytime. On the average, one cold snap each winter will manage to hold the temperature below freezing for an entire day.

By contrast, in summer the jet stream retreats to the vicinity of the U. S.-Canadian border, and cool air ceases to flow into the region from the north. Instead, a vast subtropical ridge of high pressure takes up position over Texas. At times the core of this mountain of dry, hot desert air will center over the Rio Grande Plain, forcing daytime temperatures to intolerable levels. Readi ngs above lOOF will occur in all of the region, but especially in western portions of the region where humidities are lower. The heat will intensify for several days, ultimately causing temperatures to peak out at or even above 104F.

EVAPORATION AND WATER AVAILABILITY The movement of air across Texas is not only responsible for ushering in moist and arid,

warm and cold airmasses whose interaction sometimes produces precipitation. The wind slakes the common thirst for rainwater, but it also fosters that thirst Especially during those spells in the warmer half of the year when ample sunshine and gusty, dry winds predominate, topsoil and water bodies, along with all forms of vegetation, lose immense quantities of water through the processes of evaporation and transpiration.

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This extraction of water is an important factor in reducing the quantity of water available for domestic supply or irrigation; it has almost as much an impact upon crop production as does rainfall.

Distribution of the Wind The incessant exchange of moisture within the biosphere--from the air to the surface of

Earth and from Earth back to the atmosphere--is a function of both wind speed and direction. The exchange of airmasses--and the shifting gradients of air pressure triggered by that interaction-­forces the wind to blow. The force of friction, exerted when air "rubs" against Earth's surface, produces innumerable eddies in the near-surface windflow. The result is a high degree of variability in both speed and velocity over short periods of time.

During the warmer half of the year (mid-April to mid-October) a southerly wind, or some component of it (such as a southeasterly or southwesterly wind), predominates in the Inner Gulf Coastal Plain. This dominance of airflow from the Gulf of Mexico and Chihuahuan Desert is particularly marked during summer. A wind rose for the three months of summer (June-August) for the IGCP shows that, on the average, a southerly wind, or some derivative of it, blows 90 percent of the time. During the same season, calm (windless) conditions are rare, occurring less than I percent of the time.

On the other hand, in winter, northerly winds are common in all of the IGCP. The invasion of a cold front is frequent enough (once every 4-6 days, on the average) to generate a northerly wind (or some variation) about half the time in January. Wind speeds typically accelerate as cool airmasses move out of the state and a return southerly flow is established prior to the invasion of the next cold front. Then, in the initial hours after frontal passage, winds blow vigorously, often causing wind-chill temperatures to be 20F to 40F colder than actual air temperatures.

One of the most intense winds at any time occurs within the region in the late summer and early autumn in conjunction with the movement toward the coast of a tropical cyclone. Though hurricane-force winds (74 mph or higher) are often of fairly short duration (a few hours at most) and are confmed to areas nearer the coastline, winds sufficiently strong to exact damage to property can occur inland as far as the IGCP.

Winds and Humidity The wind is but one component of the process called evaporation that is responsible for

significant water loss statewide. The rate at which the evaporative process steals water from Earth's surface is also a function of the moisture content of the air. Humidities vary moreso than air temperature across the Inner Gulf Coastal Plain on most days. Sultry conditions prevail everywhere in the region on many days during summer, and spells of high humidity occur often in other seasons as well, even in wmter. Moreover, throughout the year, humidities are higher early in the day and usually bottom out during the afternoon and early evening. Typical relative humidities in summer range from 93 percent in the hours around dawn and 53 percent at midday.

SEVERE STORM PHENOMENA Since it lies within the mid-latitude arena where airmasses of differing densities often

collide, the Inner Gulf Coastal Plain receives several severe weather outbursts each year. These outbreaks of weather violence consist of tornadoes, hailstorms, and damaging straight-line thunderstorm winds.

Impacts of Tropical Cyclones About every other year, on the average, the IGCP must contend with the deleterious effects

of a massive whirlwind that roars in from the sea. Sometimes the threat is a full-fledged hurricane, replete with incredibly strong winds, a devastating storm surge, and severe flooding. In such instances, the IGCP is less threatened than areas adjacent to the coastline. At other times, the culprit may be a lesser tropical storm capable of spawning dozens of tornadoes and torrential

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rains. In those instances, the IGCP can be at greater threat than coastal areas. Even comparatively weak tropical systems, such as depressions and "waves," have been known to engender excessive, flood-producing rains and funnel clouds. The peak period for these major weather-producing storm systems extends from early August through mid September. However, hurricanes and tropical storms have been known to strike the Texas coast as early as June and as late as mid-October.

Cyclones out of the Gulf often deliver enough rainfall to quash the kind of drought that flourishes in the IGCP in the high heat of summer. However, the rainfall from such systems is seldom evenly distributed. One sector of the IGCP may receive welcome relief, while adjacent areas collect little or no meaningful rainfall. Of course, some cyclones do more than arrest unwanted drought: they deliver torrential rains that foster disastrous flooding. The amount of rainfall from such storms varies considerably and is dependent upon the size of the rain area and the rate of movement of the storm mass. Generally, total storm rainfall, and thus the worst flooding, are greatest for broad hurricanes that drift slowly, both prior to and in the wake of landfall. However, cyclones so minor as to not qualify to be named have been known to be among the most prolific rain-producers.

Threat of Tornadoes and Other Thunderstorm-Induced Phenomena Aside from the occasional rashes of tornadoes that accompany a hurricane inland over

Texas in late summer, the tornado is a dreaded phenomena confined largely to the volatile spring season in the IGCP. Killer tornadoes are most likely to rampage in the region in April and May. Incidences of tornadoes in March and June are not uncommon, however. The late summer and early autumn may feature a rash or two of tornadoes as well, if a significant tropical disturbance (hurricane or tropical storm) migrates into Texas out of the Gulf of Mexico.

Because the severe thunderstorm most often torments the IGCP in spring, hail, one of Nature's more notable eccentricities, is an infrequent and seasonal pest, though occasionally it can be large enough to cause extensive damage.

I

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QUATERNARY FAUNAL ASSEMBLAGES FROM CENTRAL TEXAS

Ernest L. Lundelius, Jr.

Department of Geological Sciences and Vertebrate Paleontology Laboratory, Texas Memorial Museum, The University of Texas, Austin, Texas 78712 U.S.A.

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ABSTRACT

Vertebrate fossils of Quaternary age from the Texas Coastal Plain are known from many localities but faunal assemblages and sequences are poorly known. The ages of many localities are also poorly known, but all contain Bison (bison) which indicates a Rancholabrean age for them. The Pleistocene fauna of the Coastal Plain differs from that of the Edwards Plateau in the presence of Glyptotherium (a glyptodont), Glossotherium (a ground sloth), Mylohyus (long-nosed peccary) and Holmesina (a giant armadillo). The Holocene faunas are essentially modern. They differ in the presence of Microtus sp. (a vole), a holdover from the Pleistocene faunas. The early Holocene faunas lack Tayassu tayassu (collared peccary) and Dasypus novemcinctus (nine-banded armadillo) which are members of the modern fauna. The collared peccary appears to have arrived from Mexico in the late Holocene. Dasypus novemcinctus arrived in the middle of the last century.

INTRODUCTION

Quaternary faunas and faunal sequences of the Gulf Coastal Plain are poorly known. During the last century, late Pleistocene vertebrates have been found in numerous localities along streams and from gravel pits on the larger stream' terraces. However, little is known of the ages of these deposits (Hay, 1924). The best record of Quaternary faunas of Central Texas, in terms of both geographic and age coverage, comes from the Edwards Plateau. It is possible to use data from that area, in conjunction with occurrences in the Gulf Coastal Plain, to obtain some information on the faunal sequence and past ecological conditions on the Coastal Plain.

PLEISTOCENE FAUNAS

Few older Pleistocene faunas of Central Texas are known and are at present confined to the eastern edge of the Edwards Plateau. The oldest is the Fyllan local fauna from a cave fill in the city of Austin (Patton, 1965; Taylor, 1982; Holman and Winkler, 1987). This is a Mid-Irvingtonian assemblage containing Pitymys guildayi and Atopomys texensis (two extinct voles), Ondatra annectens or O. hiatidens (an extinct muskrat), Neotoma fyllanensis (an extinct packrat) and Sigmodon cf. ~. curtisi (an extinct cotton rat). The remnant magnetism of the sediments has reversed polarity indicating an age greater than 700,000 years (Mankinen and Dalrymple, 1979) •

The terrace deposits of streams crossing the Coastal Plain have produced numerous vertebrate fossils over a long period of time. Some of the earlier occurrences were reported by Hay (1924,1927). It is clear that these deposits are not all of the same age but there is very little reliable data on the ages of these deposits. There are also no generally agreed upon correlations of the terraces of the different ri ver valleys. Although attempts have been made to trace terraces of the Colorado Ri ver downstream (Weeks, 1941; Doering, 1956), the results have not been useful for relating the vertebrate faunas.

Vertebrate fossils come from at least two different terrace levels on the Brazos and Colorado Rivers. In all cases where adequate faunas are known, Bison is present which indicates a Rancholabrean age. Since at least two different terrace levels are represented, they must contain

I I

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faunas of different ages. At Austin, the lowest major terrace of the Colorado River, the First Street terrace (Weeks, 1941), has been radiocarbon dated at about 15,000 yr B. P. (Lundelius, 1992). The second major terrace, the Capitol terrace (Weeks, 1941), has produced Mammuthus sp. which indicates an age younger than 1.5 my B.P. (Lundelius, 1987).

The first major terrace of the Brazos River in Brazos and Burleson Counties has produced a fairly diverse fauna including Bison latifrons (a longhorn bison), Mammut americanum (American mastodon), Mammuthus columbi (Columbian mammoth), Equus (a horse) sp., Eremotherium mirabile (a giant sloth), Glossotherium sp. (ground sloth), Holmesina septentrionale (a large armadillo), Cuvieronius sp. (Cuvier's mastodon), Came lops huerfanensis (a camel) and Bootherium sargenti (an ovibovine). The small animals of this fauna are poorly known. The small animals of this fauna are poorly known.

A deposit in Laubach Cave in Williamson County has a Rancholabrean fauna with a radiocarbon date of 23,230+490 yr B.P. This diverse assemblage contains Glyptotherium floridanus (a glyptodont), Tremarctos floridanus (an extinct spectacled bear) and Tetrameryx shuleri (a four­horned antelope) (Lundelius, 1985). These species are not present in the latest Pleistocene faunas of Central Texas.

Deposits underlying the First Street terrace of the Colorado River at Austin, Texas have produced a typical late Pleistocene vertebrate fauna. This fauna which has been dated at about 15,000 yr. B.P. includes Bison bison antiquus (an older form of the modern bison), Equus, Mammut americanum, Mammuthus columbi, Glossotherium, Blarina carolinensis (short tailed shrew), SynaptomY3 cooperi (bog lemming), Microtus pennsyl vanicus (meadow vole) and another vole (either the pine vole or the prairie vole).

The Pleistocene vertebrate faunas of the Coastal Plain show a number of differences from those of the Edwards Plateau. Mammut americanum, Holmesina sp., Paleolama sp. (an extinct llama), Glyptotherium floridanus and Mylohyus sp. are common in Coastal Plain sites and are rare or absent from the Edwards Plateau. Castoroides sp. (a giant beaver) is not only confined to the Coastal Plain, but seems to occur only in the northern part of it. Hydrochoerus sp. (a capybara) is another form that is confined to the Coastal Plain only along the coastal section.

Fossil finds in the southern part of the Coastal Plain, particularly the inner part, mostly consist of single specimens from widely scattered localities. Farther south and southeast, closer to the coast, there are several faunal assemblages from a series of localities along Blanco Greek in Bee and Goliad Counties which have produced a diverse vertebrate fauna (Sellards, 1940; Slaughter, 1963). Taxa include Smilodon fatalis (a saber toothed cat), Mammuthus sp., Mammut americanum, two or three species of horse, Bison sp., Camelops sp., Platygonus sp. (a flat-headed peccary), Odocoileus sp. (a deer), Holmesina septentrionale, Dasypus bellus, glyptodont, ground sloth, Ondatra zibethicus (muskrat), Sigmodon hispidus, (cotton rat), Lepus sp. (a jack rabbit), Scalopus aquaticus (eastern mole), as well as unidentified bird, lizard, alligator, turtle and snake. This fauna is associated with Paleoindian artifacts (Campbell, 1940) which places its age as latest Pleistocene.

The Kincaid shelter, located just off the Coastal Plain in Uvalde County, shares the following taxa with the Bee County fauna: Came lops , Neotoma sp. (a packrat), Bison, Sigmodon hispidus, horses, deer, alligator, sloth and Lepus. However, it lacks the glyptodont which is present in the Bee County fauna. The two faunas are so alike that if faunas were known from the intervening area of the Coastal Plain they would be similar to

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these two faunas. The Pleistocene faunas of central Texas are made up of three

components: one consists of the extinct species; the second contains extant species that no longer inhabit that region; and the third consists of the modern fauna. The third group gives no informnation about the paleoenvironment except that it was within the tolerance limits of the living species. The extinct species give only general information about the paleoenvironment. Some information can be obtained from an examination of the environmental requirements of their nearest living relatives. This must be used with caution as closely related animals may have quite different habitat requirements. The distributions of some extinct species indicate limi tat ions in their tolerances but the details are not commonly clear. A number of extinct species are restricted to certain parts of the country which may give some indication about their requirements.

Extralimital extant species are much more useful as they are still living and their habitat requirements can be better determined. A number of species such as the Synaptomys cooperi (bog lemming), Microtus pennsylvanicus (meadow vole) and Sore x cinereous (masked shrew) are found today in areas of more mesic climate to the north and east of central Texas. The presence of these animals in late Pleistocene deposits in central Texas indicates that this region had more effective moisture at that time.

Another characteristic of the Pleistocene faunas of this region is the presence of associations of extant species that are now allopatric and which seem to have contradictory environmental implications. These associations have been termed "disharmonious" by Semken (1974) and "intermingled" by Graham (1985). They were first recognized in North America by Hibbard (1960) who interpreted them as indicating Pleistocene climates that were less seasonal than the present ones. These assemblages have no modern analogues and indicate a climatic regime that no longer exists.

HOLOCENE FAUIIAS

Holocene vertebrates are known from a number of localities in central Texas but, like the Pleistocene faunas, the best assemblages with the best time control come from caves on the Edwards Plateau. Most of the material comes from archaeological sites. Holocene, especially early Holocene, faunas are very poorly known from the Coastal Plain. The Berger Bluff site in Goliad County (Brown, 1987) has produced vertebrate remains of both early and late Holocene age. The early Holocene fauna includes a variety of small vertebrates still found in the area as well as Microtus sp. (either Microtus pinetorum or ~. ochrogaster). Neither species of Microtus sp. is known in that area today. Brown (personal communication, 1992) states that the age is likely 8,000-10,000 yr B.P.

Microtus sp. is known from Holocene sites from San PatriCio, Nueces, Uvalde, Jim Wells, Live Oak, Fort Bend, Goliad, Willacy and Bexar counties as late as Late Prehistoric (Steele, 1986a; Brown, unpublished). The detailed pattern of disappearance of voles from the Coastal Plain is not yet known. A relict population of Microtus pinetorum (pine vole) is known from Kerr County (Bryant, 1941) and a recently extinct population of Microtus ochrogaster (prairie vole) is known from southeast Texas and southwest Louisiana (Stalling, 1990). It is clear that one or both of these species persisted on the Coastal Plain until very late in the

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Holocene. Extralimital records of these two species, whos'1 major distributions

lie in areas of more mesic climates, have been interpreted as indicating more moist conditions during the past. In view of their late disappearance from many parts of central Texas they may indicate the persistence of locally moist localities maintained by local factors such as springs. Further information on the details of both the changes in the distributions of each of these two species and the environmental significance of these changes must await more reliable methods of distinguishing the two species on the basis of the material that is available from the fossil record.

The vertebrate faunas of central Texas have changed through the Holocene in ways other than the loss of species. A number of species that are present in the modern fauna are not found in the Pleistocene faunas. These recent immigrants from Central America are Tayassu tayassu (javelina), Tadarida brasiliensis (Mexican free-tailed bat) and Dasypus novemcinctus. The exact times of arrival of these species are not well known.

Late Holocene faunas of the Coastal Plain have a sparse record of the arrival of Tayassu tayassu in Texas. This animal has been recorded from several Late Prehistoric (circa 1300 AD) sites in Live Oak County (Steele, 1986b), Nueces County (Steele and Mokry, 1985), Kleberg County (Smith, 1984) and McMullen County (Steele and Hunter, 1986).

Another late addition to the modern fauna is Dasypus novemcinctus. A large extinct close relative, Dasypus bellus (beautiful armadillo), is known from numerous late Pleistocene faunas in Texas. It, along with Holmesina septentrionale (a giant armadillo) became extinct about 11,000 years ago. Armadillos were absent from Texas until the appearance of Dasypus novemcinctus in about 1858 (Taber, 1939; Buchanan and Talmadge, 1954) •

SUHHARY

The Quaternary vertebrate faunas of the Texas Coastal Plain give an idea of the faunal makeup and changes of the late Pleistocene and Holocene. The Pleistocene faunas of this province differ from those of the Edwards Plateau in the large mammal makeup and show some differences from north to south and from the coastal zone to the more inland areas. The Holocene faunas are essentially modern in their composition except for one holdover from the Pleistocene. The very late Holocene faunas show the first appearance of two species, Dasypus novemcinctus and Tayassu tayassu, that are prominent members of the modern fauna.

REFERENCES CITED

Brown, 1987

Brown,

Kenneth O. Early Occupations at Berger Bluff, Goliad County, Texas. Current Research in the Pleistocene, 4:3-5.

Kenneth O. -----ms. Berger Bluff: An Early Holocene Site on Coleto Creek.

Unpublished Ph.D dissertation, The University of Texas, Austin. Bryant, M.D. 1941 A Far Southwestern Occurrence of Pitymys in Texas.

Journal of Mammalogy, 22:202. Buchanan, G.D. and R.V. Talmadge

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1954

Campbell, 1940

Doering, 1956

The Geographical Distribution of States. Texas Journal of Science, T.N.

the Armadillo in 6: 142-150.

the United

Notes on Artifacts. In: E.H. Sellards, Pleistocene Artifacts and Associated Fossils from Bee County, Texas. Geological Society of America Bulletin, 51:1640-1644.

J. A. Review of Quaternary Surface Formations of Gulf Coastal Region. Bulletin American Association of Petroleum Geologists, 40(8):1816-1862.

Graham, 1985

Russell W. The Response of Mammalian Communities to Environmental Changes During the Late Quaternary. In: J. Diamond and T.J. Case (eds.), Community Ecology, pp. 300-313. Harper and Row, New York.

Hay, O.P. 1924

Hay, O.P.

The Pleistocene of the Middle Region of North Vertebrated Animals. Carnegie Institution Publication No. 322A, Washington, D.C.

America and its -- --of Was hington,

1927 The Pleistocene of the Western Region of North America and its Vertebrated Animals. Carnegie Insti tution of Washi ngton, Publication No. 322 B, Washington, D.C.

Hibbard, Claude W. 1960 An Interpretation of Pliocene and Pleistocene Climates in North

America. Annual Report, Michigan Academy of Science, Arts and Letters, 62:5-30.

Holman, J. Alan and Allsa J. Winkler 1987 A Mid-Pleistocene (Irvingtonian) Herpetofauna from a Cave in

South-Central Texas. Pearce-Sellards Series, 44:1-17. Lundelius, Ernest L. Jr. 1985 Pleistocene Vertebrates from Laubach Cave. In: C.M. Woodruff,

F. Snyder, L. De La Garza, and R. Slade (eds.), Edwards Aquifer.., Northern Segment, Travis, Williamson, and Bell Counties, Texas, Guidebook 8:41-45. Austin Geological Society, Austin.

Lundelius, Ernest L. Jr. 1987 The North American Quaternary Sequence. In: Michael O.

Woodburne (ed.), Cenozoic Mammals of North America, pp. 211-235. University of California Press, Berkeley.

Lundelius, Ernest L. Jr. 1992 The Avenue Local Fauna, Late Pleistocene Vertebrates from Terrace

Deposits at Austin, Texas. Acta Zoologica Fennica, in press. Mankinen, E.A. and G.B. Dalrymple 1979 Revised Geomagnetic Polarity Time Scale for the 0-5 my B.P.

Patton, 1965

Journal of Geophysical Research, 84:615-626. Thomas H.

A New Genus of Fossil Microtine from Texas. Mammalogy, 46(3):466-471.

Sellards, E.H.

Journal of

1940 Pleistocene Artifacts and Associated Fossils from Bee County, Texas. Geological Society of America Bulletin, 51:1627-1658.

Semken, H.A. 1974 Micromammal Distribution and Migration During the Holocene.

American Quaternary Association Abstracts, 3rd Biennial Meeting, p. 25. University of Wisconsin, Madison.

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Slaughter, Bob H. 1963 Some Observations Concerning the

Reference to Smllodon fatalis. 15( 1) :68-11.

Genus Smllodon, with Special Texas Journal of Science,

Smith, Herman Alphonso 1984 Prehistoric Settlement and Subsistence Pattern of the Baffin Bay

Area of the Lower Texas Coast. Unpublished Ph.D. dissertation, Southern Methodist University, Dallas, Texas.

Stalling, Dick T. 1990 Microtus ochrogaster. Mammalian Species, 355:1-9. Steele, 1986a

1986b

Steele, 1986

Steele, 1985

D.G. Analysis of Vertebrate Faunal Remains. In: S.L. Black, The Clemente and Herminia Hinojosa Site, 41 JW 8: A Toyah Horizon Campsite in Southern Texas. The University of Texas at San Antonio, Special Report, 18: 108-136. Center for Archaeological Research, San Antonio. Analysis of Vertebrate Faunal Remains from 41 LK 201, Live Oak County, Texas. Appendix V. In: C.L. Highly, Archaeological Investigations at 41 LK 201, Choke Canyon Reservoir, Southern Texas. The University of Texas at San Antonio, Choke Canyon Series, 11 :200-249. Center for Archaeological Research, San Antonio.

D.G. and C.A. Hunter Analysis of Vertebrate Faunal Remains from 41 MC 222 and 41 MC 296, McMullen County, Texas. Appendix III. In: G.D. Hall, T.R. Hester, and S.L. Black: The Prehistoric Sites at Choke Canyon Reservoir, Southern Texas: Results of Phase II Archaeological Investigations. The University of Texas at San Antonio, Choke Canyon Series, 10: 452-502. Center for Archaeological Research, San Anton io.

D.G. and E.R. Mokry Jr. Archaeological Investigations of Seven Prehistoric Sites Along Oso Creek, Nueces County, Texas. Bulletin of the Texas Archaeological Society, 54:281-308.

Taber, F. 1939

W. Extension of the Range Mammalogy, 20:489-493.

of the Armad illo. Journal of

Taylor, 1982

Weeks, 1941

-----Alisa Johanna

The Mammalian Fauna fr6m the Mid-Irvingtonian Fyllan Cave Local Fauna, Travis County, Texas. Unpublished Master's thesis, The University of Texas, Austin.

A.W. Late Cenozoic deposits of the Texas coastal plain between the Brazos River and the Rio Grande. University of Texas Doctoral dissertation, 261 p.

ACKHOWLEDGEKENTS

The author wishes to thank the following people for their help in preparing this paper. Dr. Thomas Hester, Director of the Texas Archaeological Laboratory at The University of Texas at Austin, provided important references and advice concerning the dating of some of the sites in South Texas; Mr. Kenneth Brown generously made available his data on the Berger Bluff site; Dr. Michael Collins of the Texas Archaeological

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Laboratory gave advice on the Kincaid Shelter; Dr. Gentry Steele provided information based on his work at the Richard Beene site; Ms. Cathleen Babuska helped with the manuscript; and my wife Judith Lundelius helped with the editing.

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A LATE PLEISTOCENE THROUGH LATE HOLOCENE FAUNAL ASSEMBLAGE FROM THE RICHARD BEENE ARCHAEOLOGICAL SITE (4lBX83l),

BEXAR COUNTY, SOUTH-CENTRAL TEXAS: PRELIMINARY RESULTS

Barry W. Baker and

D. Gentry Steele

Department of Anthropology, Texas A&M University, College Station, Texas 77843 U.S.A.

Please do not cite without permission of the authors.

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2

ABSTRACT

The faunal assemblage from the Richard Beene site represents one

of the most significant assemblages recovered from a southern Texas

archaeological site, containing one of the largest components of Early

Archaic faunal remains from the area to date. Approximately 10,000

bone, tooth, and otolith fragments were recovered from 157 cubic m of

Late Pleistocene, Paleoindian, Archaic, and Late Prehistoric deposits.

Of these, 1,449 have been identified minimally to class, representing at

least 19 distinct taxa. Fish, freshwater turtle, and beaver indicate

the proximity of riparian habitats. Mammalian taxa identified to genus

consist of fauna typical of the Tamaulipan and Balconian Biotic

Provinces which compose the site area today. The presence of ringtail

in the Late Pleistocene deposits is particularly significant, being the

second Pleistocene record for this species in the region. The recovery

of fauna from or near hearths, and one piece of worked rabbit bone

.documents humans as one of the main taphonomic agents responsible for

bone at the site. Assuming that the majority of the bone from the Late

Paleo indian and later components represents predominantly human refuse,

the subsistence pattern resembles that seen at other hunter/gatherer

assemblages examined from southern Texas.

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INTRODUCTION

Archaeological investigations were conducted at the multicomponent

Richard Beene site (4lBX83l) from November 1990, through August 1991, by

the Archaeological Research Laboratory, Texas A&M University. The site,

located in the lower Medina River Valley in southwestern Bexar County

about 15 miles south of San Antonio, contains Late Pleistocene through

Late Holocene rleposits (McGraw and Hindes, 1987; Thoms, 1991:4; see also

Thoms in this volume). Approximately 10,000 vertebrate remains were

recovered from 1/4 and 1/8 inch mesh screens. Continuing analysis of

the sample is underway at the Archaeological Research Laboratory, and

Zooarchaeological Research Laboratory, Department of Anthropology, Texas

A&M University. The faunal analysis is one component of an

interdisciplinary study focusing on the Applewhite Reservoir

Archaeological Project. The faunal assemblage will be used to address

research questions of past land use systems, site formation processes,

and paleoenvironmental conditions. The goal of this analysis is to

provide a broad preliminary examination of the assemblage to aid later

detailed archaeological studies (See also Derring and Bryant; Mandel;

Mandel and Jacob; Neck and Fredlund; and Thoms in this volume for

discussions of other aspects of the Applewhite Reservoir Archaeological

Project).

ENVIRONMENTAL SETTING

The environmental setting of the project area is mixed and

complex. Bordering the site to the north is the Balconian Biotic

Province, which centers on the Edwards Plateau. To the south lies the

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4

Tamaulipan Biotic Province (Blair, 1950:102-115). The junction of these

provinces forms a rich and diverse biotic community consisting of post

oak and brushy species, tall and short grasses, and bottomland flora

including pecan, cottonwood, elm, and willow. The vertebrate fauna of

the Balconian Province is a mixed assemblage consisting of

Austroriparian, Tamaulipan, Chihuahuan, and Kansan species (Blair,

1950:112). The Tamaulipan Biotic Province immediately to the south

contains these species plus taxa more typical of Mexico: On a regional

scale, this wide diversity of transitional bottomland and upland species

between the two provinces would have provided a rich environment for

prehistoric cultural exploitation. The site setting is presently a

floodplain/terrace, riparian environment. Black (1989:12-14), McGraw

and Hindes (1987:39-42), and authors in this volume provide reviews of

paleoenvironmental data for the area.

METHODS

The faunal remains discussed here were recovered by water

screening soil matrix at the site through 1/4 and 1/8 inch hardware

cloth. Additional fauna from surface collections, backhoe trenches,

fine screens, and flotation samples have yet to be analyzed. For this

analysis, taxa counts were hand tabulated and recorded by time period

(Table 1). Counts reflect identifications made thus far. Many of the

elements were identified only to broad levels such as small sized

mammal, medium sized mammal, etc. Identifications will become more

refined with further analysis, though data on broad taxonomic class and

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animal size categories will continue to be comparable to the data

presented here.

5

NISP (number of identified specimens) is used in Table land

Figure 1 to refer to specimens identified minimally to the level of

class. The term "bone" in Figure 1 is used broadly to include data on

teeth and otoliths. Broken elements which could be fitted together were

counted as one specimen. Mandibulary or maxillary portions containing

teeth were also counted as one specimen. In the final analysis, each

tooth in a mandible/maxilla will be coded separately, to allow for

specific MNI (minimum number of individuals) determination. Thus, raw

specimen counts for certain taxa may increase significantly. Mammal

size categories listed in Table 1 are defined as follows: small mammal

(up to cottontail rabbit sized); small rodent (mouse sized); medium

mammal (canid, caprine sized); large mammal (deer, pronghorn sized);

very large mammal (bison sized).

THE ASSEMBLAGE

The recovered assemblage consists of 10,6B2 specimens from

discrete Late Pleistocene (ca. 12,500 yr B.P.), Late Paleo indian (ca.

B,BOO yr B.P.), Early Archaic (ca. 6,900 yr B.P.), Middle Archaic (ca.

4,500-5,000 yr B.P.), Late Archaic (ca. 3,000 yr B.P.), and Late

Prehistoric (ca. 1,000 yr B.P.) components (Table 2). While the faunal

sample is relatively small compared to two of the largest Late

Archaic/Late Prehistoric and Early Ceramic assemblages from southern

(4lLK201) and southeastern (4lHR273) Texas (Table 2), the sample is

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6

particularly noteworthy for the large Late Pleistocene and Early Archaic

components, and the well stratified nature of the assemblage.

The state of preservation of the assemblage is variable. The Late

Pleistocene component has remarkably well preserved bone with many

complete elements. Some of the Late Pleistocene fragments exhibit

spiral fractures indicating the breakage occurred while the bone was

still fresh. Nine definitely burned fragments, possibly from a single

long bone of a small vertebrate, were recovered from this component as

well, though no unequivocal artifacts or cultural features were found in

the Late Pleistocene deposits.

The taphonomic condition of the Archaic assemblages is more

difficult to interpret at the present time. The average Early through

Late Archaic bone fragment is smaller than Late Pleistocene fragments

(Fig. l and Table 2). For the most part, elements from the Archaic are

more fragmented, with some specimens showing fine line cracking and

abrasive wear on the edges. Interpretation of the nature of deposition

that created these conditions awaits further analysis. Many of the bone

fragments from the site are burned. The Late Paleoindian and Late

Prehistoric assemblages are relatively small and poorly preserved,

showing the lowest densities of specimen weight and count (Fig. 1 and

Table 2).

Of the 10,682 vertebrate fragments, approximately l4~ have been

identified to the five taxonomic classes (Table l and Fig. 2).

Minimally, 19 species are present in site, with 11 of these identified

to genus or species. The Late Pleistocene deposits contain some of the

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7

best preserved faunal remains (N-3,039) including skeletal elements of

frog/toad, water turtle, softshell turtle, snake, perching bird, rabbit,

squirrel, cotton rat, ringtail, deer, and bison sized mammal (See TAXA

QESCRIPTIONS and Table 1). The bison-sized fragments from the Late

Pleistocene represent the only very large taxa recovered from the site.

The presence of ringtail is particularly noteworthy since only one other

specimen of this taxon has been reported from Pleistocene deposits north

of Mexico (Semken, 1961:304). Dalquest et al. (1969:216-217) noted that

ringtail was not recovered from Pleistocene deposits at Schulze Cave in

nearby Edwards County, and implied the species may have colonized the

region only within the Late Holocene. The recovery of ringtail from

Late Pleistocene deposits dated to 12,500 yr B.P. (from associated

charcoal) at the Richard Beene site supports Semken's assessment that

the species has been endemic to the region since the Pleistocene.

The sample size for the Late Paleo indian component is currently

much smaller (N-726), with only 25 specimens identified to class. These

faunal remains were recovered from strata that yielded a wide variety of

cultural material, including intact and partially intact features. Some

of the bone is burned. Taxa include fish, snake, small mammal, rabbit,

small rodent, gopher, woodrat, and unidentified artiodactyl (even-toed

ungulates).

The Early Archaic deposits yielded the largest cultural faunal

assemblage from the site (N-4,850). Mammals and lower vertebrates

(fish, amphibians, and reptiles) dominate the assemblage, as is true of

the combined Archaic assemblage (Figure 2). Early Archaic taxa include

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8

fish, mud/musk turtle, softshell turtle, snake, rabbit, small rodent,

squirrel, gopher, cotton rat, woodrat, porcupine, carnivore, canid,

unidentified artiodactyl, deer, pronghorn/deer, pronghorn, and

unidentified small, medium and large sized mammals. The most abundant­

taxa (in terms of NISP) are medium/large mammals, rabbits, and small

mammals. The rabbit assemblage is interesting in that over 140 elements

were recovered. A large portion of these are complete mandibular rami,

representing several individuals. This high frequency of leporid

remains is also seen in Late Archaic and Late Prehistoric sites from

Tamaulipan assemblages to the south (e.g. Hellier et al., ms. :1280-1282;

Steele, 1986a:134-l35, 1986b:237-239; Steele and Hunter, 1986:485-491).

The only culturally modified bone from the site, a single worked rabbit

radius, is also from the Early Archaic component.

Both charred (burned black) and calcined bones (burned white) were

encountered in the Early Archaic assemblage, and weathering and

degradation ranged from slight to marked. Spiral fractures are present

on several medium/large mammal long bone fragments. The Early Archaic

fauna appears to have the greatest potential for addressing questions of

cultural activity and subsistence at the site, making this a highly

significant site for Southwestern U.S. archaeology.

The Middle Archaic assemblage is relatively small (N-229), though

comparatively less area was excavated than for the Early Archaic

component (Table 2). Only 15 specimens have been identified to class.

Only mammals have been noted thus far, including small, medium and large

sized mammals, small rodent, artiodactyl, and pronghorn/deer. Charred,

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calcined, and spirally fractured bone is present. Specimens range from

slight to heavily weathered.

The Late Archaic vertebrate assemblage (N-l,798) includes

frog/toad, cf. water turtle, snake, rabbit, small rodent, gopher,

beaver, wood rat, canid, artiodactyl, deer, pronghorn/deer, and

unidentified small, medium and large sized mammals. Post-cranial

elements of medium-to-Iarge sized mammals, and artiodactyl tooth

fragments dominate the assemblage. Charred, calcined, and spirally

fractured bone is present. Specimens range from slight to heavily

weathered.

9

Three bones have been identified to class from the Late

Prehistoric (N-40), this component being the least intensively excavated

(Table 2). Taxa from the Late Prehistoric deposits include frog/toad,

snake, and large mammal. Charred and calcined bone, and specimens with

slight and heavy weathering are present.

There are some general statements that can be made from the faunal

data set concerning the local environment of the Richard Beene site.

The fauna recovered includes at least three kinds of water turtles,

fish, and beaver. These clearly document the proximity to water,

possibly the nearby Medina River, tributaries of this river, or springs.

Ringtail, porcupine, woodrats·, cotton rats, pronghorn, and white-tailed

deer, elements all of which were recovered from the site, are species

common to the present day local Tamaulipan and Balconian Biotic

Provinces. The fauna from the Early Archaic component suggests that the

biotic community has been relatively stable within the region during the

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10

Holocene. The presence of ringtail suggests that at least one Mexican

species typical of the region today, existed during the Late Pleistocene

as well.

During this preliminary stage, only a general assessment of

prehistoric subsistence can be made. Overall, the recovered taxa

resemble assemblages from other human habitation sites from southern and

central Texas that we have examined. Rabbits, cotton rat, woodrat,

deer, and turtles are common, suggesting the sites' occupants followed a

subsistence lifestyle typical of other hunters and gatherers of southern

Texas.

TAXA DESCRIPTIONS

Presented below are descriptions of taxa identified from the site to

date. The recovered material is described, with references to other

southern Texas sites that have yielded similar taxa. This regional

comparison is not meant to be exhaustive, but represents comparison of

selected taxa from archaeological sites in the Tamaulipan Biotic

Province analyzed primarily by the junior author.

Class OSTEICHTHYES (Bony Fish)

Referred material: 1 otolith (Late Paleoindian); 1 vertebra, 3 otoliths

(Early Archaic).

Discussion: A left sagitta otolith was recovered from Late Paleo indian

deposits at the site. From the Early Archaic deposits, two right and

one left sagitta otolith were identified. At least three fish, one from

Late Paleoindian and two from Early Archaic deposits, are represented in

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the assemblage. All four otoliths resemble the sunfish family

(Centrarchidae, Order Perciformes) (McClure, 1991:14).

Class AMPHIBIA; Order ANURA (Frogs and Toads)

Referred material: 2 long bones (Late Pleistocene); 2 long bones (Late

Archaic); 1 long bone (Late Prehistoric).

Class REPTILIA; Order TESTUDINATA (Turtles and Tortoises)

Referred material: Unidentified turtle shell fragments have been noted

thus far from Late Pleistocene, Early Archaic, and Late Archaic

deposits.

11

Discussion: The majority of specimens identified to the level

Testudinata are hard shell turtles, exclusive of the soft-shelled turtle

family Trionychidae. Soft-shelled turtles are easily distinguished from

other families by their characteristically dimpled shells. The majority

of the turtle bone is from Late Pleistocene deposits and probably

represents water turtle (Chrysemys sensu 1ato). At least three turtles

are represented from the Late Pleistocene, one being a softshell turtle.

with two other turtles of different size also present. Turtle shell

fragments, in conjunction with snake vertebrae, account for the high

density of lower vertebrates illustrated for the Late Pleistocene in

Figure 1.

Family KINOSTERNIDAE (Mud and Musk Turtles)

Referred material: 2 shell fragments (Early Archaic).

Site records: This family has been reported from 4lLK28 (Hellier et al.,

ms.:1269), 4lLK20l (Steele, 1986b:226-227), and 4lMC296 (Steele and

Hunter, 1986:480).

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Discussion: Kinosternidae is represented by two genera in Texas:

Kinosternon (mud turtle), and Sternotherus (musk turtle) (Dixon,

1987:79-81). Of the five Kinosternidae species occurring in Texas, ~

flavescens, K. subrubrum, and S, odoratus occur in Bexar County today

(Dixon, 1987:176-181). These species are highly aquatic and their

presence at the site suggests nearby riparian environments.

Family EHYDIDAE; Genus Chrysemys (sensu lato) (Water Turtles)

12

Referred material: 3 carapace fragments from Late Pleistocene deposits.

Site records: This genus has been reported from 41LK28 (Hellier et al.,

ms.:1268), 41JW8 (Steele, 1986a:129) , 41LK20l (Steele, 1986b:226), and

41MC222 and 41MC296 (Steele and Hunter, 1986:479).

Discussion: The use here of the taxon Chrysemys (sensu lato) follows

Weaver and Rose's (1967) inclusion of painted turtles, cooters, and

sliders within a single genus. Chrysemys (sensu stricto) reflects the

placement of the painted turtles within their own genus, with cooters

placed in Pseudemys, and the sliders included within Trachemys.

Controversy exists even today, however, concerning which classification

system most accurately reflects the relationship of these turtles

(Seidel and Smith, 1986). Because of difficulty involved in identifying

water turtle genera from carapace fragments (Sobolik and Steele,

ms. :12), Weaver and Rose's (1967) classification is followed here.

cf. Chrysemys (sensu lato) (Water Turtles)

Referred material: 9 shell fragments (Late Pleistocene); 1 shell

fragment (Late Archaic).

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Family TRIONYCHIDAE; Genus Trionyx (Softshell Turtle)

Referred material: 1 shell fragment (Late Pleistocene); 2 shell

fragments (Early Archaic).

13

Site records: This genus has been recovered from 41LK28 (Hellier et al. ,

ms.:1270), 41LK20l (Steele, 1986b:227-228), and 41MC296 (Steele and

Hunter, 1986:480).

Discussion: Two species of Trionyx occur in Texas. These are T, muticus

(smooth softshell turtle) and T, spiniferus (spiny softshell turtle)

(Dixon, 1987:86-87). Only T spiniferus is known from Bexar County

today (Dixon, 1987:195-196). Habitats include marshy creeks, ponds,

lakes, and rivers. T, muticus rarely leaves the water, though ~

spiniferus often basks along banks and logs exposed in the water (Ernst

and Barbour, 1972:258, 262). Soft-shelled turtles are easily

distinguished from other families by their characteristically dimpled

shells. Consequently, they are typically over represented .in taxonomic

frequency lists.

Order SQUAMATA; Suborder SERPENTES (Snakes)

Referred material: 213 complete and fragmented vertebrae from all time

periods at the site, exclusive of the Middle Archaic.

Discussion: Generic and species identification of snakes from skeletal

elements is difficult, despite work by authors such as Auffenberg

(1969). While identification to the family level (Colubridae vs.

Viperidae) has proven simpler based on ventral process morphology, none

of the vertebrae retained complete ventral processes. A detailed

analysis of the snake vertebrae from the site has yet to be undertaken.

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14

Class AVES (Birds)

Referred material: 16 post-cranial elements (Late Pleistocene).

Discussion: Many of these elements are complete and may be identifiable

with additional analysis. The majority are the size of large perching

birds such the cardinal.

Order PASSERIFORHES (Perching Birds)

Referred material: 1 humerus (Late Pleistocene).

Class MAMMALIA; Order LAGOMORPHA; Family LEPORIDAE (Rabbits and Hares)

Referred material: 200 cranial and post-cranial elements from Late

Pleistocene, Late Paleoindian, Early Archaic, and Late Archaic deposits.

Discussion: Leporids are represented by two genera in Texas, Sy1vi1agus

and Lepus (Schmid1y, 1983:104-115). Species which occur in the Bexar

County today include S. floridanus (eastern cottontail), S. auduboni

(Audubon cottontail), S, aguaticus (swamp rabbit), and L. californicus

(black-tailed jack rabbit) (Davis, 1974:236-244). Morphological

similarities and size overlap between S, aguaticus and L, californicus,

along with degradation of the sample, make distinction between these

taxa uncertain for most elements.

Genus Sylvilagus (Rabbits)

Referred material: 1 post-cranial (Late Pleistocene); 3 post-cranial

(Early Archaic); 2 post-cranial (Late Archaic).

Site records: Rabbits have been reported from 41LK28 (Hellier et al.,

ms.:128l-1282), 4lJW8 (Hester, 1977; Steele, 1986a:135), 4lLK201

(Steele, 1986b:237-239), 41MC222 and 41MC296 (Steele and Hunter,

1986:486-491), and 4lZV14, 41ZV60, 4lZV152, (Hester et al., 1975:227).

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15

Discussion: Sylvilagus is represented by three species in Bexar County:

S. floridanus (eastern cottontail), S. auduboni (Audubon cottontail),

and S. aguaticus (swamp rabbit) (Davis, 1974:236-244; Schmidly,

1983:104-111). Specimens were included in Sylvilagus based on their

small size.

Order RODENTIA; Small-Sized Rodents Indeterminate

Referred material: From all time periods excluding the Late Prehistoric.

Discussion: "Small rodent" is defined here as mouse-sized. The majority

of these specimens are incisors and long bone elements. Much of the

material tentatively classed as small mammal is probably also of the

order Rodentia.

Family SCIURIDAE (Squirrels)

Referred material: 3 teeth from the Late Pleistocene and Early Archaic.

Site records: The family sciuridae has been identified from 4lLK28

(Hellier et al., ms. :1274-1275).

Discussion: Squirrels in the Bexar County area may be divided into

ground squirrels [Spermophilus mexicanus (mexican ground squirrel), ~

variegatus (rock squirrel), and Cynomys ludovicianus (black-tailed

prairie dog)], and tree squirrels [Sciurus carolinensis (eastern gray

squirrel), and S. niger (fox squirrel)], with S. niger being the most

common tree squirrel (Davis, 1974:146-164).

Family GEOHYIDAE (Pocket Gophers)

Referred material: 1 tooth (Late Paleoindian); 2 teeth (Early Archaic);

1 post-cranial element (Late Prehistoric).

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Site records: Gophers have been reported from 41LK28 (Hellier et al.,

ms. :1275-1276), 41JW8 (Hester, 1977; Steele, 1986a:136), and 41MC296

(Steele and Hunter, 1986:491).

16

Discussion: Three gopher genera occur in Texas today, including

Thomomys, Geomys, and Pappogeomys (Davis, 1974:164-171). Without upper

incisors, morphological distinction of gopher genera from skeletal

material is often difficult. The classification of Texas geomyids in

general is complex (Jones and Jones, 1992:60-62). Many of the currently

recognized species of Geomys, for example, are identified principally

from chromosomal and biochemical differences. Taxa which occur in and

near Bexar County today include G. personatus (south Texas pocket

gopher), G, bursarius (plains pocket gopher), and G, attwateri

(Attwater's pocket gopher) (Davis, 1974:169; Schmidly 1983:138).

Despite the fact that gophers spend much of their time underground,

there is sufficient evidence to indicate they were exploited by North

American indians, and therefore should not be ignored as a possible food

source for the inhabitants of the site (Shaffer, 1991:132-136, and

references therein).

Family CASTORIDAE; Species Castor canadensis (Beaver)

Referred material: 1 tooth (Late Archaic).

Family CRICETIDAE (New World Rats and Mice); Genus Sigmodon (Cotton Rat)

Referred material: 8 elements (Late Pleistocene); 8 elements (Early

Archaic).

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17

Site records: This genus has been reported from 41LK28 (Hellier et al.,

ms.:1279), 4lJW8 (Steele, 1986a:136), 41LK20l (Steele, 1986b:243),

41MC222 and 41MC296 (Steele and Hunter, 1986:492-493).

Discussion: Of the three extant Texas Sigmodon species (Jones and Jones

1992:66), only S, hispidus (hispid cotton rat) occurs in the region

today.

Genus Neotoma (Woodrat)

Referred material: 3 elements (Late Paleoindian); 5 elements (Early

Archaic); 2 elements (Late Archaic).

Site records: The genus Neotoma has been reported from 41LK28 (Hellier

et al., ms.:1277-1278), 41JW8 (Steele, 1986:135), 41LK201 (Steele,

1986:241), 41MC222 and 41MC296 (Steele and Hunter, 1986:492).

Discussion: Three woodrat species occur today in, or near, Bexar County.

These include Neotoma albigula (white-throated woodrat), N. floridana

(eastern woodrat), and N. micropus (southern plains woodrat) (Jones"and

Jones, 1992:66; Schmidly, 1983:197-205). N, floridana prefers riparian

habitats, while N. micropus and N. a1bigula are more cornmon in semiarid

or xeric environments (Davis, 1974:221; Schmidly, 1983:197, 202).

cf. Neotoma (Woodrat)

Referred material: 1 element (Late Archaic).

Family ERETHIZONTIDAE; Species Erethizon dorsaturn (Porcupine)

Referred material: Mandible portion with teeth (Early Archaic).

Discussion: The specimen is the distal portion of right mandible

retaining M,-M,. The animal was a sub-adult, showing no wear on the

erupting right third molar. Jones and Jones (1992:67) noted that the

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18

eastward range of extant porcupines in Texas extends at least to Kerr

County, though no specimens are known from Bexar County, located just to

the southeast (Davis, 1974:232).

Order CARNIVORA (Carnivores)

Referred material: 8 teeth (Late Pleistocene); 1 tooth (Early Archaic).

Discussion: These are teeth of primarily medium-sized carnivores that

have yet to be identified.

Family PROCYONIDAE; Species Bassariscus astutus (Ringtail)

Referred material: 4 dental, 5 post-cranial elements (Late Pleistocene).

Site records: Ringtai1 remains have been reported from Late Pleistocene

deposits at Longhorn Cavern, Burnet County, Texas (Semken, 1961:304).

cf. Bassariscus astutus (Ringtail)

Referred material: 1 post-cranial element (Late Pleistocene).

Family CANIDAE (Canids); Genus Canis (Dogs and Relatives)

Referred material: 1 anterior portion of a mandible (Late Archaic).

Site records: Canis has been reported from 41JW8 (Steele, 1986:133),

41K201 (Steele, 1986:234), 41MC222 and 41MC296 (Steele and Hunter,

1986:484-485).

Discussion: Species of Canis whose ranges have included the project area

include C. latrans (coyote), C, lupus (gray wolf), and C. rufus (red

wolf) (Davis, 1974:123-129; Jones and Jones, 1992:68; Schmidly,

1983:234-245).

cf. Canis (Dogs and Relatives)

Referred material: 1 tooth fragment (Early Archaic).

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Order ARTIODACTYLA (Artiodactyls)

Referred material: Primarily tooth enamel fragments from all time

periods exclusive of the Late Prehistoric.

Discussion: These are primarily small tooth fragments that exhibit

artiodactyl morphology, but could not be identified to family.

Family CERVIDAE; Genus Odocoileus (Deer)

19

Referred" material: 1 tooth (Late Pleistocene); 12 tooth/fragments, 2

post-cranial elemertts (Early Archaic); 5 tooth/fragments (Late Archaic).

Site records: Deer remains are common throughout archaeological sites in

the region.

Discussion: Specimens were identified as deer based on Lawerence's

(1951) criteria used in conjunction with comparative material.

Morphological overlap between Odocoileus virginianus (white-tailed deer)

and Odocoileus hemionus (mule deer) often makes osteological

differentiation between the two difficult. However, current range and

habitat information indicates that the sample is probably representative

of Odocoileus virginianus (Jones and Jones, 1992:72). White-tailed deer

are common in all vegetational zones in Texas, with bottomland hardwoods

being the preferred habitat. Odocoileus virginianus is the only deer

currently found in the project area (Schmidly, 1983:295).

Antilocapra/Odocoileus Indeterminate (Pronghorn/Deer)

Referred meterial: From Early, Middle, and Late Archaic deposits.

Discussion: These are primarily long bone portions which were

unidentifiable to deer or pronghorn.

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Family ANTlLOCAPRIDAE; Species Antilocapra americana (Pronghorn)

Referred material: 1 medial phalanx (Early Archaic).

20

Discussion: This toe bone was identified as pronghorn based on

comparison with modern material, and with Lawrence's (1951:25) criteria

of proximal end morphology. Currently, pronghorn are restricted to the

panhandle and western portion of the state (Davis, 1974:248). Formerly,

pronghorn occupied the western portion of Texas as far east as Robertson

and McLennan counties (Jones and Jones, 1992:72).

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21

ACKNOWLEDGMENTS

Research at the Richard Beene site was funded by the San Antonio Water

Board. Investigations were carried out by the Texas A&M Archaeological

Research Laboratory under contract to Freese & Nichols, Inc. The U.S.

Army Corps of Engineers, Fort Worth District, oversaw the project.

David L. Carlson, Brian S. Shaffer, and Alston V. Thoms provided

valuable comments on the manuscript. Ben W. Olive assisted in creating

the tables and figures. Alston V. Thoms and Patricia A. Clabaugh

provided continual feedback and information about the site, with

detailed field and laboratory control.

Page 115: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

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Auffenberg, Walter

1969 The Fossil Snakes of Florida. Tulane Studies in Zoology,

10:131-216.

Black, Stephen L.

1989 Environmental Setting. In: Thomas R. Hester, Stephen L.

22

Black, D. Gentry Steele, Ben W. Olive, Anne A. Fox, Karl J.

Reinhard, and Leland C. Bement (eds.), From the Gulf to the

Rio Grande: Human Adaptation in Central, South, and Lower

Pecos Texas, pp. 5-16. Arkansas Archeological Survey

Research Series No. 33.

Blair, W. Frank

1950 The Biotic Provinces of Texas. The Texas Journal of

Science, 2(1):93-117.

Da1quest, Walter W., Edward Roth, and Frank Judd

1969 The Mammal Fauna of Schulze Cave, Edwards County, Texas.

Bulletin of the Florida State Museum, 13(4):205-276.

Davis, William B.

1974 The Mammals of Texas. Bulletin No. 41, Texas Parks and

Wildlife Department, Austin.

Dixon, James R.

1987 Amphibians and Reptiles of Texas: With Keys, Taxonomic

Synopses, Bibliography, and Distribution Maps. Texas A&M

University Press, College Station.

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23

Ernst, Carl H. and Roger W. Barbour

1972 Turtles of the United States. University Press of Kentucky,

Lexington.

Hellier, Jana R., D. Gentry Steele, and Cristi A. Hunter

ms. Analysis of Vertebrate Faunal Remains. In: Anna Jean Taylor

and Cheryl Lynn Highley (eds.), Archaeological

Investigations at the Loma Sandia Site (4ILK28): A

Prehistoric Cemetery and Campsite in Live Oak County, Texas,

pp. 1233-1285. Texas State Department of Highways and

Public Transportation, Highway Design Division, Contract

Reports in Archaeology, Austin.

Hester, Thomas R.

1977 Archaeological Research at the Hinojosa Site (41JW8). Jim

Wells County, Southern Texas. Center for Archaeological

Research, The University of Texas at San Antonio,

Archaeological Survey Report 42.

Hester, Thomas R., T. C. Hill Jr., Diane Gifford, and Sally Holbrook

1975 Archaeological Salvage at Site 41ZV152, Rio Crande Plain of

Texas. The Texas Journal of Science, 26(1-2):223-228.

Jones, J. Knox, Jr. and Clyde Jones

1992 Revised Checklist of Recent Land Mammals of Texas, with

Annotations. The Texas Journal of Science, 44(1):53-74.

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Lawrence, Barbara

1951 Part II. Post-cranial Skeletal Characters of Deer,

Pronghorn, and Sheep-Goat with Notes on Bos and Bison.

Papers of the Peabody Museum of Archaeology and Ethnology,

Harvard University, 35(3). Cambridge, Massachusetts.

McClure, W. L.

24

1991 Otoliths of Some Texas Fish (Centrarchidae and Sciaenidae).

Texas Archeology, 35(1):14.

McGraw, A. Joachim and Kay Hindes

1987 Chipped Stone and Adobe: A Cultural Resources Assessment of

the Proposed Applewhite Reservoir, Bexar County, Texas.

Archaeological Survey Report No. 163. Center for

Archaeological Research, The University of Texas at San

Antonio.

Schmidly, David J.

1983 Texas Mammals East of the Balcones Fault Zone. Texas A&M

University Press, College Station.

Seidel, Michael E. and Hobart M. Smith

1986 Chrysemys, Pseudemys, Trachemys (Testudines: Emydidae): Did

Agassiz Have it Right? Herpetologica, 42(2):242-248.

Semken, Holmes A., Jr.

1961 Fossil Vertebrates from Longhorn Cavern Burnet County,

Texas. The Texas Journal of Science, 13(3):290-310.

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25

Shaffer, Brian S.

1991 The Economic Importance of Vertebrate Faunal Remains from

the Nan Ruin (LA 15049), A Classic Mimbres Site, Grant

County, New Mexico. Unpublished Master's thesis, Texas A&M

University, College Station.

Sobolik, Kristin D. and D. Gentry Steele

ms. A Turtle Atlas to Facilitate Archaeological Identifications.

On file in the Zooarchaeological Research Laboratory,

Department of Anthropology, Texas A&M University, College

Station.

Steele, D. Gentry

1986a Analysis of Vertebrate Faunal Remains. In: Stephen L. Black

(ed.), The Clemente and Herminia Hinojosa Site, 41JW8: A

Toyah Horizon Campsite in Southern Texas, pp. 108-136.

Special Report No. 18. Center for Archaeological Research,

The University of Texas at San Antonio.

1986b Appendix V. Analysis of Vertebrate Faunal Remains from

I . \ 41LK20l, Live Oak County, Texas. In: Cheryl Lynn Highley

(ed.), Archaeological Investigations at 4lLK20l, Choke

Canyon Reservoir, South Texas, pp. 200-249. Choke Canyon

Series, Vol. 11. Center for Archaeological Research, The

University of Texas at San Antonio.

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26

Steele, D. Gentry and Cristi A. Hunter

1986 Appendix III. Analysis of Vertebrate Faunal Remains from

41MC222 and 41MC296, McMullen County, Texas. In: Grant D.

Hall, Thomas R. Hester and Stephen L. Black (eds.), The

Prehistoric Sites at Choke Canyon Reservoir, Southern Texas:

Results of Phase II Archaeological Investigations, pp. 452-

502. Choke Canyon Series, Vol. 10. Center for

Archaeological Research, The University of Texas at San

Antonio.

Thoms, Alston V.

1991 Applewhite Reservoir: Mitigation Phase Excavations at

41BX831, The Richard Beene Site. APR News and Views,

3(2):4. Department of Archeological Planning & Review,

Texas Historical Commission, Austin.

Weaver, W. G. and F. L. Rose

1967 Systematics, Fossil History, and Evolution of the Genus

Chrysemys. Tulane Studies in Zoology, 14:63-73.

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, r Figure 1. Selected densities (per cubic m) illustrating total lithic

count, total vertebrate count, total vertebrate weight (g), NISP (number

, 1 of identified specimens to class), and average vertebrate specimen

weight (g), per time period.

Figure 2. Relative taxa densities (per cubic m) for lower vertebrates

; (fish, amphibians, and reptiles), birds, and mammals by time period.

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Table 1. Taxa by Preliminary NISP' Counts (Number of Identified Specimens) from 41BX831.

Time Period Late Late Early KiddIe Late Late Total P1eist. Paleo. Archaic Archaic Archaic Prehist.

Castor canadensis (Beaver) 1 1

Sigmodon (Cotton rats) 8 8 16

Neotorna (Woodrats) 3 5 2 10

cf. Neotoma (Woodrats) 1 1

Erethizon dorsatum (Porcupines) 1 1

Carnivora (Carnivores) 8 1 9

Bassariscus astutus (Ringtails) 9 9

cf. Bassariscus astutus 1 1

Canis (Canids) 1 1

cf. Canis (Canids) 1 1

Artiodactyla (Artiodactyls) 5 2 3 1 32 43

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._ ...

Table 1, Taxa by Preliminary NISI'" Counts (Number of Identified Specimens) from 4lBX83l,

Time Period Late Late Early Middle Late Late Total Pleist, Paleo, Archaic Archaic Archaic Prehist,

Odocoileus (Deer) 1 14 5 20

AntilocaBraL Odocoileus (Pronghorn/deer) 6 1 1 8

Antiloca:era americana (Pronghorn) 1 1

Period Total 743 25 559 15 113 3 1,449

aNISP counts include taxa identified minimally to Class (Fish, Amphibian, Reptile, Bird, Mammal), Note: Taxa counts are not inclusive (ex, Testudinata counts do not include identified turtles such as Kinosternidae , Chrysemys, Trionyx, etc.).

·cf,-compares favorably with, <For taxa size descriptions: S-small; SjM-small to medium; M-medium; M/L-medium to large; L-large;

VL-Very large, See Methods section for definitions of animal size ranges,

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Table 2. Comparative sample Data for Selected South-Central, Southern, and South-East Texas Archaeological Vertebrate Assemblagesa •

Site & Period

41BX831 Late Pleistocene Late Paleo indian Early Archaic Middle Archaic Late Archaic Late Prehistoric Total Sample

41LK201 (Steele 1986) Late Archaic and Late Prehistoric

41HR273 (Baker et al. 1991) Early-Late Ceramic

Mesh

1/4" +

1/811

1/4 11

+ 1/8"

1/4" +

1/16"

N

3,039 726

4,850 229

1,798 40

10,682

13,671

59,094

Wt (g)

929.75 84.83

1,134.98 34.40

275.41 3.30

2,462.67

34,789

m3

5.6271 60.1679 37.2205 12.7627 36.1211

4.6100 156.5093

3.4

6.4

Wt/N

0.3 0.1 0.2 0.2 0.2 0.1 0.2

0.6

N/m3

540.1 12.1

130.3 17.9 49.8 8.7

68.3

4,021

wt/m3

165.2 1.4

30.5 2.7 7.6 0.7

15.7

9,233 5,436

aMesh=recovery screen size; N=sample size; Wt=weight in g; m3=volume excavated in cubic m; Wt/N=average specimen weight in g; N/m3=count density (per cubic m); wt/m3=weight density (per cubic m).

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PLANT REMAINS FROM TilE RIC liARD BEENE SITE (41BX831): IMPLICATIONS FOR HOLOCENE CLIMATIC CHANGE IN

SOUTH-CENTRAL TEXAS

J. Philip Dering and Vaughn M. Bryant, Jr. Palynology Laboratory, Texas A&M University, College Station, Texas 77843 U.S.A.

INTRODUCTION

Excavation of the Richard Beene Site (41BX831) on the Applewhite Terrace of the Medina

River revealed a sequence of deeply stratified cultural and biological remains. A series of

radiocarbon ages indicated that the terrace deposit ranged in age from about 3,100 to 32,000 yr

B.P. (Thoms, 1991). Twenty-five soil samples from the potentially culturally significant levels

(3,100 B.P. to c.a. 15,000 B.P.) were collected and processed for pollen analysis. In addition, 21 samples containing carbonized wood were examined for identification.

CURRENT VEGETATION

The Applewhite Terrace of the Medina River is located 25 km south of San Antonio on the Texas coastal plain. Blair (1950) has characterized the region south of San Antonio as arid sub­

humid or moist sub-arid, and has placed it in the Tamaulipan biotic province. The sub-arid environment is created by megathermal temperatures with an evaporation rate that exceeds the

area's precipitation. The study area is situated in the north central part of the South Texas Plains vegetational zone, a few kilometers south of its junction with the Edwards Plateau to the north,

and the Blackland Prairie to the northeast (Hatch, et al., 1990). the The Applewhite formation consists of an active flOOdplain and three terraces that rise above

it, each with a characteristic vegetation community. The terrace (T-2) immediately overlooking the main Applwehite formation consists of a Holocene mantle draped over a red alfisol of Plio­

Pleistocene age and is dominated by blackbrush acacia (Acacia rigidula), huisache (Acacia

farnesiana), mesquite (ProSQpis elandulosa), and various buckthorns (Rbamnaceae) and cacti. '

The main surface of the Applewhite formation (T-!), which stretches between the low-lying Pliocene-age hills of T-2, is consists of abandoned cotton fields characterized by a weedy

mesquitelhuisache scrub. The Applewhite escarpment overlooks the active floodplain, and is dominated by the more xeric mesquite, acacias, retama (Parkinsonia aculeata,), and prickly pear mixed with live oak. The active floodplain is characterized by Texas riparian vegetation including dense stands of huge pecan trees (~ illinoiensis), cypress (Taxodium distichum) soapberry

(Sapindus saoonarial, hackberry (~sp.), sycamore (Platanus sp.) and elm (Ulmus sp.). , and mesquite (Prosopis), oak (Ouercus), and thorny scrub brush land, including members of the

buckthorn (Rhamnaceae) and cactus (Cactac~e) families.

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PALEOVEGETATION OF SOUTH TEXAS: PREVIOUS STUDIES The ute Pleistocene and Holocene vegetation record for the region of the South Texas

Plains is very incomplete. The south Texas region lacks peat bogs, suitable lakes containing

lengthy deposits, and dry caves where botanists might be able to obtain sufficient plant remains or

fossil pollen to reconstruct vegetational chronologies. In addition, where deeply strati tied

archeological deposits have been studied, the high soil pH, low soil organic content, and poorly

drained soils of the south Texas region have yielded only meager traces of badly degraded fossil

pollen in quantities too small for analytical purposes from a large number of test samples collected

at archaeological sites and processed by us.

The nearest well-studied archeological sites within the South Texas Plains are located in the

Choke Canyon Reservoir area, 120 km to the south. Pollen preservation, however, around Choke

Canyon was very poor. The alkaline soils and the high oxidation rate in the sediments do not allow

for the preservation of the normally durable pollen grains (Havinga, 1964; Hall, 1981). As a

result, paleovegetational research in the south Texas region has yielded only meager traces of

pollen in quantities too small for analytical purposes. Pollen and plant macrofossil studies from areas adjacent to the South Texas Plains help to

establish the paleovegetational context Peat bogs located just beyond the eastern periphery of the

South Texas Plains, in Gonzales County, have yielded a rich Late Pleistocene and Holocene

vegetation record. In addition, studies of the dry caves of the Lower Pecos and Devil's Rivers

region have established a long vegetational sequence for that area. When combined with the

meager data from the South Texas Plains, we can begin to get a picture of the paleovegetation of

the region during the Late Pleistocene and Holocene.

Late Glacial Period--14,000-1O,OOO Years B.P.

The late-glacial in Texas represents a transitional period characterized by a slow climatic

deterioration which is noted in the fossil pollen record by the gradual loss of woodland and

parkland areas in many regions of the state. Because no late-glacial pollen or plant macrofossil records are available from south Texas, we must draw on other records to set the stage for

examining the late-glaciallHolocene transition of the region. In west Texas and in regions of the

Llano Estacado in northwest Texas the late-glacial is characterized as a period when existing areas

of conifers at the lower elevations were replaced by open grasslands while conifer forests at higher elevations remained more or less stable. In southwest Texas the existing vegetation developed a

broad mosaic pattern during the late-glacial period with scrub grasslands beginning to cover larger

areas of the landscape at the expense of the remaining pinyon-juniper woodland and parkland

regions. In central Texas the deciduous woodland regions began to disappear and were replaced

by grasslands and oak savannas (Bryant and Holloway, 1985).

The apparent late-glacial loss of arboreal taxa is seen in the fossil pollen record of Hershop

Bog, Gonzales County, Texas, 120 km east of the Applewhite Terrace (Larson, et al., 1972). Peat

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deposits radiocarbon dated as being near the end of the late-glacial period in Hershop Bog note an

overall reduction in arboreal pollen and a total loss of birch (Betula nigra) pollen. Currently, birch grows in regions of east Texas where the annual rainfall is in excess of 1.016-1,270 mm. In

addition, the closest known present stands of birch are 415 km northeast of Hershop Bog. Those data suggest that during the late-glacial period, south-central Texas climates probably were wetter

and perhaps cooler than the climate in that region today. In southwest Texas, fossil pollen records recovered from Bonfire Shelter are not well­

dated below the Holocene. Nevertheless,suspected late-glacial deposits at that site reflect regional trends similar to those found in other areas (Bryant, 1969). decreasing percentages of pine pollen

accompanied by rises in grass, composite and mormon tea (Ephedra) pollen just prior to the onset of the post-glacial period at Bonfire Shelter suggest nearby areas of pinyon and juniper woodlands

were being reduced in size while the amount of grasslands and scrublands was steadil y increasing. This proposed shift in the vegetational composition of the lower Pecos River area during the late­

glacial period may have resulted from a variety of factors including a suspected reduction in river discharge and reduced availability of ground water moisture caused by higher evaporation rates

resulting from warmer summer temperatures. By examining the data which geographically brackets the South Texas Plains, we can infer

that the region experienced a gradual warming and drying trend during the late-glacial to Holocene transistion. The lack of direct fossil evidence, however, prevents us from making a more detailed

statemenl

Holocene Period--I 0,000 B.P. To Present No post-glacial fossil pollen records exist for the region of south Texas. Archeobotanical

studies are available for the region of south Texas and they can be used to formulate a few generalized statements about the post-glacial vegetation. Holloway (l986) has examined a number

of charcoal samples recovered from archaeological deposits spanning the last 6,000 years in the Choke Canyon region (Fig. 1) south of the Applewhite Terrace. In that study Holloway found

, that the primary fuel sources used by local aboriginal groups consisted of Acacia spp. and mesquite (Prosopis). To a lesser degree these same aboriginal groups also used tire wood from

riparian sources which included willow (~, pecan(~), and perhaps persimmon (Diospyros). Based upon those findings Holloway (1986) suggested that during the last 6,000

years of the post-glacial period the Choke Canyon region of south Texas contained a vegetation very similar to that area's current vegetation and that no apparent major vegetational changes

occurred in that time span. Steele's (in press) analysis of faunal remains recovered from some of the same Choke

Canyon archaeological sites studied by Holloway (in press) revealed a mixture of animal usage by aboriginal groups during the past 6,000 years. Recovered faunal remains from those sites

included taxa such as the raccoon (Proyon locto), opposum (Didelphis virgineanus), and muskrat (Ondatra zibethicus) which represent types generally associated with wooded areas similar to some

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PRESERVATION AT TIlE APPLEWHITE TERRACE Pollen and plant macrofossil analyses form the data base for many types of interpretations

ranging from sequential changes in past environments to information about the Ii festyles and diets

of prehistoric human populations. In each of these studies, the eventual interpretation of botanical data must account for all factors that may have influenced the composition of the original pollen

rain, factors that may have altered the composition of the buried pollen assemblage, and the post­depositional processes that may have affected the plant macrofossil assemblage.

At the Applewhite Terrace, an open site, one would expect to find only charred plant remains, and a good possibly of adequately preserved pollen or phytoliths. Unfortunately, the

conditions for preservation were apparently very poor for all categories of plant remains. As noted in Table 2, only 5 out of24 specimens of charcoal exhibited sufficient remaining cellular structure

to be able to make and identification. Polien was virtually nonexistent below the Leon Creek

paleosol.

Pollen

During the last 50 years palynologists have learned that there are many complex factors that determine the original composition of the pollen rain in a region. These include factors such as:

type of pollination; differences in pollen production; differential dispersion patterns; and the size, weight, and aerodynamic ability of pollen types to remain airborne. Once deposited, other factors

influence eventual loss or recovery of specific pollen types. These factors include: pollen recycling, the chemical composition of a pollen grain's exine, its morphological shape and surface

ornamentation type, and its susceptibility to various types of degradation processes including those from mechanical, chemical, or biological agents (Bryant 1978, 1988; Bryant and Jones 1989;

Bryant and Holloway 1983; Holloway 1989). It is this last category, the post depositional degradation process, that is the focus of this report.

One of the first agents that can affect pollen grains is mechanical degradation. After pollen is released from its source, it can become abraded or broken during the transportation phase.

These alterations can result from impact or from changes in the natural environment. Studies by Duhoux (1982), for example, have shown that changes in atmospheric moisture levels can result

in high numbers of exine ruptures in closely related, thin walled pollen taxa such as Taxodium, Juniperus, and I!!J!ja. Later, after being deposited, these thin walled pollen types as well as other

types of grains can become further abraded by the cultural activities of humans such as burning, land surface modifications; construction activities, and agricultural practices. Abrasion of pollen

can also occur from various causes in the natural environment such as impact against objects, water and wind erosion, changes in temperature, changes in atmospheric or soil moisture contents,

volcanic eruptions, and soil movement. The morphological structure and ornamentation of pollen walls seem to be important

factors in determining their potential susceptibility to mechanical degradation. For example, pollen grains having protruding structures, like the bladders of many conifer species or the spines of

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some Malvaceae grains, have a tendency for their projections to break off or erode through a

variety of mechanical processes. In some cases, the actual appearance of a pollen grain may become so altered after the loss of an appended structure, or structures, 'that accurate identification

is no longer possible. In addition, structural alteration by mechanical processes can also cause severe exine weakening, thereby hastening the eventual destruction of the entire grain through

other processes.

Soil chemistry, acting on the natural chemical composition of a pollen grain's exine, or

outer wall, is another factor that seems to play an important role in pollen preservation. Although the exine is mostly composed of a highly durable material called sporopollenin, certain

environmental factors can adversely affect it. Brooks and Shaw (1968), Shaw (1971), Rowley

and Prijanto (1977), and Rowley (1990) found that differences in sporopollenin composition and

molecular structure can make pollen grains either more, or less, resistant to chemical deterioration. Using the effects of pH as an example, Dimbleby (1957) was one of the first to chart

differences in pollen preservation caused by soil chemistry. His research revealed that soils with a

low, acidic pH are ideal deposits for pollen preservation while sediments with a pH above 6.0

often result in the destruction of fossil pollen. Since Dimbleby's original study in the late 1950s, other studies conducted in the arid regions of the American Southwest by Martin (1963), Bryant

(1969), and Hall (1981) have demonstrated that fossil pollen can be recovered from alkaline soils

with a pH as high as 8.9. Even when this is possible, however, the recovered pollen has often

deteriorated; a fact that makes accurate pollen analyses difficult, and in some cases nearly impossible.

Related to Dimbleby's (1957) original work on pH is Tschudy'S (1969) research on the Eh

(oxidation potential) of sediments. Tschudy (1969) asserts that Eh actually may be a more

important guide to the eventual preservation or destruction of palynomorphs than is pH. Low Eh reflects a reducing, anaerobic, environment where carbon dioxide and hydrogen sulfide are the by­

products of microbe respiration and combine to decrease the pH values. Thus, in some sediments

the creation of a negative Eh potential results in the formation of a strongly-reducing environment

(Tschudy 1969). Because a reducing environment retards oxygen retention, the resulting low Eh environment becomes an ideal environment for pollen preservation. Likewise, an oxidizing

sediment with a high Eh speeds the destruction of pollen.

The chemical composition of pollen walls and pollen wall structural morphology also play

important roles in determining whether or not pollen grains will remain preserved in various sediments. In a 20-year study beginning in 1964 and ending in 1984, Havinga (1964, 1984)

reported that the relationship between the percentage of sporopollenin to cellulose in the wall of

pollen grains seems to affect their susceptibility to eventual destruction through oxidation. He

found, for example, that pollen grains having high percentages of sporopollenin in their walls tend

to remain preserved longer, even in soils with high Ph and Eh values, than do pollen grains with

walls composed mostly of cellulose. Recently, Rowley ~. (1990) have conducted detailed

SEM studies of the processes of pollen destruction in various soil types and report these results

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though the presentation of detailed photomicrographs.

Biological agents, such as fungi and bacteria, can cause pollen grain degradation. Recent studies (Holloway 1981) show that some taxa of Phycomycete fungi seek out and feed on the

nutrient materials in the cytoplasm of pollen grains. His experimental studies show that the

filamentous threads of fungi, called hyphae, often enter a pollen grain through natural aperture

openings; yet at other times they dissolve areas of the exine in order to enter the grain. Both types of attack contribute to the eventual destruction of pollen grains by creating new holes in the exine

or enlarging tiny cracks in the exine thus weakening the overall grain and making it more susceptible to other forms of degradation.

Some years earlier, Phycomycete fungi were investigated by Goldstein (1960) who found they were a causative factor in the destruction of pollen. Data from his initial study showed that

some taxa of Phycomycetes are selective in their preference for pollen types and will infect certain

pollen taxa at a much faster rate than others. For example, he found pollen grains from certain

species of coniferous trees, especially Pseu90tsU1:a, were attacked much more frequently by

Phycomycetes than were types of angiosperm pollen. Unlike Holloway's (1981) study,

Goldstein did not focus on how fungi actually damage pol\en grains. Instead, his data concluded only that pollen from many conifer taxa are the most susceptible types to fungi infection, and thus

by inference, eventual destruction. Elsik (1966) noted that bacterial degradation of pollen grains also occurs. He found that

certain bacteria, especially types of Actinomycetes, degrade pollen walls in a definite pattern. He found that in some cases this type of bacterial destruction can continue to occur long after pollen

grains have lost their cytoplasm and have become preserved in sedi ments for thousands, or even millions, of years (Elsik 1966).

Carbonized Plant Remains

Charred plant remains are essentially inert, resulting in increased resistance to decomposition. Destruction by reduction, however, can occur from processes such as trampling,

pressures caused by soil movement, freeze/thaw, or burrowing of animals (Bryant, 1989). Reduction is often viewed as the first phase of plant destruction since it is defined as the

alteration of plant materials into smaller pieces through mechanical breakdown. Reduction is a very destructive action since it also hastens the second phase, decomposition, by creating

additional surfaces which are then exposed to decay. Sometimes the reduction process of plant I (

remains is so complete that the residue consists of millions of tiny microscopic fragments about the

size of coffee grounds. Once this stage of reduction is reached, identification of plants is very difficult (Bryant, 1989).

The second of these modification processes is decomposition, which is defined as the decay and digestion of plant materials by chemical or biological sources. A number of inorganic

and organic acids and bases will dissolve cellulose or weaken it to such a degree that mechanical

reduction is rapid. Many of these substances are carried through the soil by ground water (Bryant,

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1989).

Chemical decomposition of plant materials plays an important role in preservation,

especially at the Applewhite Terrace. Of the three main compounds found in the walls of plant

cells cellulose is the easiest to oxidize, lignin is next, and sporopollenin is the hardest to oxidize.

Havinga (1964) reported that the ratio of sporopollenin to cellulose in the walls of pollen grains

directly affects their susceptibility to oxidation. The higher the amount of sporopollenin a grain

has, the less likely it is to oxidize. Because pollen is generally one of the plant remains most

resistant to decomposition, the amount, kind, and condition of fossil pollen is often a good guide

to the overall level and potential for organic preservation (Bryant, 1989).

Holloway (1981) showed that a number of specific chemical compounds can be classified

as important plant decomposition agents. Interestingly, eight of the nine compounds tested were

bases, and 3 of these contained carbonate. The Applewhite Terrace sediments are very basic and

are very rich in carbonates.

During the processing and examination of charcoal samples the condition of the specimens

varied from exhibiting good structure to completely lacking any internal structure whatsoever. The

most poorly preserved samples were little more than a black powder imbedded in a sediment

matrix. The most likely explanation for such degradation would be a combination of reduction and

chemical processes involving the following: 1) basic pH levels, 2) percolation of carbonate rich

ground water, and 3) expansion and contraction of brought on by continual wetting and drying of

the site's sedimen ts.

SUMMARY Pollen and plant macrofossil analyses were conducted on sediments from the Richard

Beene site (4lBX831), a deeply stratified archeological site located in the Applewhite Terrace of

the Medina River. Results of the analysis indicated that very poor conditions of preservation

prevailed at the site. Despite the poor preservation, the recovery from 10,000 year-old deposits of

bois d'arc charcoal, which currently grows to the north and east of the study area, indicate the

possibility of more mesic conditions at that time.

Other plant remains indicate little c~ange in the riparian vegetation of the Medina River

valley as reflected in the deposits of the Applewhite Terrace. The pollen record from the last

3,000 years indicated that modern vegetation patterns were probably in place by that time. The

presence of oak and mesquite in deposits in the 4,000-5,000 B.P. range, fail to demonstrate any

change in the Holocene riparian vegetation.

Conditions of poor preservation probably are attributable to 1) very high pH levels. 2)

percolation through of carbonate rich ground water, and 3) expansion and contraction brought on

by continual wetting and drying of the sediments. The size of the fossil pollen and plant macrofossil assemblage must be considered when

weighing the validity of any conclusions regarding Holocene vegetation change in the study area.

These preliminary results from the botanical investigations at the Richard Beene site on the

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Applewhite Terrace do not contradict the general trends indicate by other studies within the region

or adjacent to the region. Further analyses will serve to refine this description of Holocene vegetation change at the Applewhite Terrace.

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REFERENCES CITED

Bicchieri, M.G.

1972

Blair, 1950

Hunters and Gatherers Today. Winston, New York.

will iam. F. The Biotic Provinces of Texas. Science, 2(1):93-113.

Holt, Rhinehart, and

The Texas Journal of

Brooks, J. and Shaw, G.

1968 Chemical structure of the exine of pollen walls and a new function for carotenoids in nature. Nature 219:523-524.

Bryant, Vaughn M., Jr.

1969

1989

Late full-glacial and post-glacial pollen analysis of Texas sediments. Ph.D. dissertation (Dept. of Botany), The University of Texas, Austin, Texas, 168 p.

Preservation of biological remains from archaeological sites. In: Interdisciplinary Workshop on the Physical­Chemical-Biological Processes Affecting Archaeological Sites (edited by C. Mathewson). pp. 85-115. U.S. Army Corp of Engineers Waterways Experiment station, Vicksburg.

Bryant, Vaughn M., Jr., and Riskind, David H.

1980 The paleoenvironmental record for northeastern Mexico: A review of the pollen evidence. In: Epstein J. F. , Hester T. R., and Graves C. (eds. ), Papers on the Prehistory of Northeastern Mexico and Adjacent Texas. Center for Archaeological Research Special Report, 9 (San Antonio, Texas): 7-31.

Bryant, Vaughn M., Jr., and Richard G. Holloway

1985 A Late-Quaternary Paleoenvironmental Record of Texas: An Overview of the Pollen Evidence. In: V.M. Bryant, Jr. and R.G. Holloway (eds.) ,Pollen Records of Late­Ouaternary North American Sediments, pp. 39-70.

Bryant, Vaughn M. Jr. and John G. Jones

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1989 Pollen analysis of samples collected from archaeological sites along the route of the all American pipeline. In: cultural Resources Report for the All American pipeline Project. (edited by All American Pipeline Company). pp 316-365. New Mexico state University, Las Cruces.

Bryant, Vaughn M., Jr. and James Schoenwetter

1987 Pollen records from Lubbock Lake. In: Lubbock Lake Late Quaternary Studies on the Southern High Plains (edited by E. Johnson) pp 36-40. Texas A&M University Press, college station.

Dering, J. Philip

1979 Pollen and plant macrofossil vegetation record recovered from Hinds Cave, Val Verde county, Texas. M.S. Thesis, Texas A&M University, college Station, Texas, 79 p.

Dimbleby, G.W.

1957

Duhoux. E.

1982

Pollen analysis of terrestrial soils. 56:12-28.

New Phytologist

Mechanism of exine rupture in hydrated taxoid type of Pollen. Grana 21:1-7.

Elsik, William K.

1966 Biologic degradation of fossil pollen grains and spores. Micropaleontology 12:515-518.

Goldstein, S.

1960 Destruction of pollen by Phycomycetes. 41:543-545.

Ecology

Gunn, Joel, Hester, Thomas R., Jones, R., Robinson, Ralph L., and Mahula, R.A.

1982 Climate change in southern Texas. In: Hall,G., Black, S. ,and Graves C. (eds.), Archaeological investigations at Choke Canyon Reservoir, South Texas: The Phase I findings. Center for Archaeological Research, San Antonio, Texas, Choke Canyon Series, 5 : 578-597.

Hall, Steven A.

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1981 Deteriorated Pollen Grains and the Interpretation of Quaternary Pollen Diagrams. Review of Paleobotany and Palynology, 32:193-206.

Harper, Kay T, and G.M. Adler

1970 The Macroscopic Plant Remains of Hogup Cave, utah, and Their Paleoclimatic Implications. In: G.M. Adler (ed.), Hogup Cave. Anthropological Papers 93:215-240. University of Utah, Salt Lake City.

Hatch, Stephan L., K.N. Gandhi, and Larry E. Brown

1990 Checklist of Agricultural Texas.

the Vascular Plants Experiment station,

of Texas. college

Texas station,

Havinga, A.J.

1964

1984

Investigations susceptibility 6:621-635.

into the differential corrosion of pollen and spores. Pollen et Spores

A 20-Year experimental investigation into the differential corrosion susceptibility of pollen and spores in various soil types. Pollen et Spores 26:541-558.

Holloway, Richard G.

1981 Preservation and exine. Ph. D. (Botany), College

experimental diagenesis of dissertation, Texas A&M Station, Texas, 317 p.

the pollen University

Holloway, Richard G.

1986 Macrobotanical analyses of charcoal materials from the Choke Canyon Reservoir area, Texas. In: Hall, G. D. , Hester, T.R., and Black, S.L. (eds.), The Prehistoric sites at Choke Canyon Reservoir, Southern Texas: Results of the Phase II Archaeological Investigations. Center for Archaeological Research, San Antonio, Texas, Choke Canyon Series No. 10.

Larson, David A., Vaughn M. Bryant, Jr. and Thomas. S. Patty.

1972 Pollen analysis of a central Texas bog. Midland Naturalist, 88: 358-367.

Lee, Richard B.

24

American

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1969 What Hunters Do for a Living. In: R.B. Lee (ed.), Man the Hunter, pp. 30-48, Aldine, Chicago.

Robinson, Ralph L.

1979

1982

Biosilica and climatic change at 41GD21 and 41GD21A. In: Fox, D. E. (ed.), Archaeological investigations of two prehistoric sites on the Coleto Creek Drainage, Goliad County, Texas. Center for Archeological Research, San Antonio, Texas, Archaeological Survey Report 69:126-138.

Biosilica analysis of three prehistoric archaeological si tes in the Choke Canyon Reservoir, Live Oak County, Texas: Preliminary summary of climatic implications. In: Hall,G., Black, S., and Graves, C. (eds) , Archaeological Investigations at Choke Canyon Reservoir, south Texas: the Phase I findings. Center for Archaeological Research, San Antonio, Texas, Choke Canyon Series, No.5,: 597-610.

Rowley, John R., J.S. Rowley and J. Skvarla

1990 Corroded exines from Havinga I s leaf mold experiment. palynology 14:53-80.

Shafer, Harry J.

1975 Clay Figurines from the Lower Pecos Region, Texas. American Antiguity,40(2):148-158.

STEELE, D. G.

1986 Analysis of vertebrate faunal remains from 41MK201. In: Hall, G.D., Hester, T.R., and Black, S.L. (eds.), 1985 The Prehistoric sites at Choke Canyon Reservoir, Southern Texas: Results of the Phase II Archaeological Investigations. Center for Archaeological Research, San Antonio, Texas, Choke canyon Series, No. 11.

Thoms, Alston V.

1991 Floodplain Environments and Archaeological Assemblages in the Lower Medina River Valley, south Texas. Paper presented at the 49th Annual Plains Conference, Lawrence, Kansas.

Tschudy, R.H.

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1969 Relationship of palynomorphs to sedimentation. Aspects of Palynology. (edited by R. Tschudy and R. Scott), pp 79-96. Wiley & Sons, New York.

Watts, W.A.

1973 Rates of Change and Stability of vegetation in the Perspective of Long Periods of Time. In: Quaternary Plant Ecology. Blackwell Scientific publications, Oxford.

Wells, Philip v.

1976 Macrofossil Analysis of Wood Rat (Neotoma) Middens as a Key to the Quaternary Vegetational History of Arid America. Journal of Quaternary Research, 6(2):223-248.

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Table 1. Pollen Types (Percentages) From the Leon Creek Paleosol

sample

Taxon 1 2 3 4 5

Pinus 1.4 0.9 0.4 2.4 5.0

Ephedra 0.9 0.9

Taxodium 5.0

Quercus 1.4 2.7 1.2 3.8 14.3

Carya 0.9 2.7 0.5

Fraxinus 1.4 1.8 0.8 0.5 2.5 ,

I Ilex 0.5

Myrica 0.5 1.4 0.4

I Cornus 0.4

Platanus 0.5 0.4

I Ulmus 0.5 0.8

Celtis 0.5 5.4 3.2 2.4 4.2

Salix 0.4 0.4 0.8

Cylindropuntia 0.5

Liquidambar 1.3 0.4 0.4

Poaceae 3.5 9.4 25.4 8.9 8.8

L.S. Compositae 66.1 35.9 38.6 41.0 25.8

H.S. Compositae 6.2 5.4 6.0 3.7 3.3

Liguliflorae 4.0 5.9 1.2 1.2 4.2

Cheno-Am 0.9 4.5 6.6 16.7

Convolvulaceae 0.5 0.5

Cyperaceae 0.9

Euphorbiaceae 0.4

Fabaceae 0.5 0.9 0.4 0.5

Alnus 0.9 I. I

Apiaceae 0.5

Lamiaceae 0.4

Malvaceae 0.4 0.8

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Mimosaceae 0.4 0.4

Nyctaginaceae 0.4

Liliaceae 0.8 0.5

Polygonaceae 0.4 0.4 1.5

Rosaceae 0.5 0.4

Scrophulariaceae 0.5

onagraceae 2.8

Eriogonum 4.9 2.8

Artemisia 0.9 0.4 0.4 0.5

Eleaginaceae 0.5

Unknown 0.4

\ Indeterminate 4.0 11.2 8.8 13.2 4.6

Total 100 100 100 100 100

I Lycopodium 79 22 38 44 35 Tracers

Concentration 3,161 11,454 7,464 5,445 7,749

I Value (grains/mIl

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· . Table 2. Carbonized Plant Remains From the Richard Beene Site.

BOTANICAL BLOCK NORTHING/ ELEV. FEATURE ANALYSIS RESULTS SAMPLE EASTING AKSL TYPE NUMBER LEVEL

BOT-l GC N976 E1064 153.62f FEA 73 FLOAT/1O NO (51) EARLY Z13·S3·L1 153.4 STRUCTUREI

ARCHAIC NDET

BOT-2 G N978 153.58 FEA 76 CHARRED NO (30) EARLY E1061·62 TREE WOOD 10 STRUCTURE

ARCHAIC BURN INDET

BOT-3 G N978 E109l 153.44/ FEA 44 CHARRED NO (32) EARLY Z13·SS·Ll 153.30 WOOD 10 STRUCTURE

ARCHAIC INDET

BOT-4 G N988 E1032 153.53 FEA 30 CHARRED NO (31) EARLY WOOD 10 STRUCTURE

ARCHAIC INDET

BOT-S GC N96S E1065 153.42/1 FEA 74 FLOAT/1O NO EARLY Z13-S3·Ll 53.35 STRUCTURE

ARCHAIC INDET

BOT-6 G N988 E1033 153.60/1 FEA 30 FLOAT/ID NO (50) EARLY Z13-S1·Ll 53.50 STRUCTURE

ARCHAIC INDET

BOT-7 GB N977 E1091 153.48/ FEA 43 CHARRED NO EARLY Z13-SS·7 153.42 WOOD 10 STRUCTURE

ARCHAIC INDET

BOT-8 H BHT 1 151. 50 FEA 31 FLOAT/1O QUERCUS LATE (OAK)

PALEO

BOT-9 HA N923 E1l54 151.14/1 NONE FLOAT/1O RING LATE Z14-S2-L1 51.04 POROUS

PALEO INDET HARDWOOD

BOT-10 K N1063 148.25 FEA 80 FLOAT/1O NO (53) LATE E1061 STRUCTURE

PALEO Z19·L59 INDET

BOT-ll K N1063 148.33/1 FEA 80 CHARRED QUERCUS (59) LATE E1061 48.20 WOOD 10

PALEO Z19-L59

BOT-12 0 N960 150.92 FEA 108 CHARRED MESQUITE/A LATE E1063 WOOD 10 CACIA

PALEO

BOT-13 T N939 149.45/1 NONE CHARRED DIFFUSE (34) LATE Ell06 49.28 WOOD 10 POROUS

PALEO INDET. DICOT

BOT-14 T N943 Ell07 149.55/1 NONE WOOD ID NO (36) LATE 49.45 STRUCTURE I. PALEO Zp·A-3 INDET I

BOT-1S T N939 Ell06 149.65/1 NONE CHARRED NO (55) LATE 49.55 WOOD 10 STRUCTURE

PALEO INDET

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\ I BOTANICAL BLOCK NORTHING/ ELEV. FEATURE ANALYSIS RESULTS

SAMPLE FASTING AHSL TYPE NUMBER LEVEL

BOT-16 T N939 El106 149.56/1 NONE CHARRED NO (58) LATE ZP-A-4 49.46 WOOD ID STRUCTURE

PALEO INDET

BOT-l7 T N939 149.45/1 NONE CHARRED NO LATE El106 49.28 WOOD ID STRUCTURE PALEO INDET

BOT-18 S N933 144.06/1 NONE FLOAT/ID NO (56) NON- E1l47 43.9 STRUCTURE

CULTURAL SOIL 7B INDET LEVEL 9

BOT-19 S N922 143.98/1 NONE FLOAT/ID NO (57) NON- E1l47 43.8 STRUCTURE

CULTURAL SOIL 8 INDET LEVEL 10

BOT-20 S BRT 39 144.26 FEA 95 CHARRED QUERCUS (33) NON- WOOD ID (OAK)

CULTURAL

BOT-2l N952.24 147.06/ BRT 54 FLOAT/ID QUERCUS (35) Ell02.28 146.94 ROLF'S (OAK)

N952.36 Ell03.78

BOT-22 SAME AS SAME AS SAME AS CHARRED NO (54) ABOVE ABOVE ABOVE WOOD 1D STRUCTURE

INDET

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LATE PLEISTOCENE AND HOLOCENE ENVIRONMENTS IN TIlE MEDINA VALLEY OF TEXAS

AS REVEALED BY NONMARINE MOLLUSCS

Raymond W. Neck Houston Museum of Natural Science

INTRODUCTION Late Quaternary sediments associated with 41BX831 in alluvial deposits of the Medina

River in Central Texas have been examined for molluscan remains. Nineteen species, representing freshwater bivalves and gastropods as well as terrestrial gastropods were recovered from these sediments. Reconstructed plant communities include marsh, wet meadow, savannah, and short- to mid-grass prairie. Surface waters were present for part of the time represented in this column and flood debris input was a source of a significant number of shells. Relative stability in the molluscan paleofauna is probably the result of distance from glacial fronts, nearness of moderating maritime influences, and partial control of vegetational communities by edaphic factors. The limited species diversity exhibited by the lowermost levels may be partially the result of taphonomic factors as well as limited diversity of the source fauna.

The existence of deep. stratified alluvial sediments in the Medina Valley of southern Bexar County, Texas, has presented an opportunity to investigate the environmental history of this region from the Late Pleistocene through the Holocene to the present. This opportunity is significant for several reasons. The sediments present at 41 BX831 present the opportunity to analyze the Late PleistoceneIHolocene time period for changes in the microhabitats available to nonmarine molluscs. The results of any analysis of paleoassemblages from this area are likely to be significant for several avenues of research: Late Quaternary history of the transition zone between the piedmont of central Texas and the Coastal Plain, environmental changes in a geographical locality that is far removed from any glacial front of the Pleistocene, and taphonomic factors that affect the relationship between the paleofauna and the paleoassemblage that is extracted from the sediments.

The lower Medina Valley is located in the transition zone between the Balconian and Tamaulipan biotic provinces as delineated by Blair (1950). Although all such boundary lines are conceptual models, the delineation between these two biotic provinces is rather sharp. However, there are noted edaphic islands or lineal dispersal routes that can be observed from modern dispersal patterns or inferred from relictual populations. Investigations that analyze the prehistory of this area have the opportunity to reveal variations in geographical aranges of various species that are classified as either Balconian or Tamaulipan. Sufficient variation from the modern distributional patterns may also indicate the need to postulate temporal shifts in the boundary zone between these two biotas.

Very little discussion on the history of the boundaries between biotic provinces in central Texas has been published, although Durden (1974) discussed the history of the biotic provinces of North and Central America over time periods much longer than the Pleistocene. Gehlbach (1991) recently published his thoughts concerning the environmental barriers on the eastern margin of the Balconican Biotic Province and the alleged early Holocene origin of this boundary.

The paleoenvironmental history of the South Texas Plains, a term that applies to most of the Tamaulipan Biotic Province in southern Texas, is largely unknown. However, a few molluscan paleoassemblages from southern Texas have been reported with variable attempts at analysis. Hubricht (1962) reported seven species of terrestrial gastropods from "loess, near San Antonio River, 5 miles south of San Antonio." Five of the species

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reported in this paleoassemblage are moderate to large-shelled species that occur in this region today. However, two small-shelled species present in the assemblage are not found living in the area today. Hubricht (1962) provided only limited comments on the paleoenvironmental significance of this "loess" sample, except to note that the occurrence of one of extralimital species indicated "that the climate was colder and wetter when these deposits were laid down than at present." No estimate of age, other than Pleistocene, was given for this assemblage.

Other paleoassemblages from southern Texas have been reported. Hubricht (1962) also reported the occurrence of a very species-diverse assemblage in "loess" near Palo Blanco Creek west of Falfurrias. This assemblage contained a number of aquatic gastropods that are characteristic of northern and southern modem faunas. The terrestrial gastropod species recorded from this assemblage include only species that can be found in central and southern Texas today, although not necessarily in the immediate vicinity of his collection locality. Neck (1987) reported a stratified paleoassemblage from near Uvalde, Texas, just south of the Balcones Escarpment Zone. These sequential assemblages represent diffferent vegetational and edaphic environments that are best interpreted as a series of natural successional stages and do not require any change in macroclimate. All species present in the various layers in this site are living in the immediate area of the site today. Other analyses of nonmarine molluscan paleoassemblages from southern Texas have involved sites that were closer to the coast. Neck (1983) reported on a low-diversity assemblage extracted from Late Pleistocene sediments associated with a tributary of Los Olmos Creek in Kleberg County. The recovered assemblage indicated a slight increase in effective moisture but no major changes in molluscan microhabitats. Another paleoassemblage from the extreme southern part of Texas in Cameron County involved a mixed brackish and freshwater species assemblage that has more relevance to postulated Holocene sea level changes (Neck, 1985) than inland nonmarine environmental changes.

METHODS A series of three-liter samples were removed from 32 proveniences at 41 BX83 I.

These samples ranged from the modem soil surface to buried strats identified as Late Pleistocene. The modem soil has been designated as Venus clay loam by the U. S. Soil Conservation Service (Taylor et al., 1966); other stratigraphic names are from unpublished work of Mandel, Thoms, and others. A stratigraphic ,summary of these samples is presented in Table I. The 32 samples taken were identified as follows:

Im- 0-25 cm, mesquite covered area near the PresnallWatson barn, If- 0-25 cm, plowed field near the slurry trench, 2- above the Leon Creek paleosol, 3- Leon Creek paleosol, 4- 18 cm below Leon Creek paleosol, 5- lower portion of the Leon Creek paleosol, 6- sandy zone above Medina paleosol, 7- top of Medina paleosol, 8- Bk of Medina paleosol, 9- Bk of Medina paleosol, 10- Bk of Medina paleosol, 11- Bk of Medina paleosol, 12- lower Medina paleosol, 13- CB horizon of Medina paleosol, 14-laminated zone above the Elm Creek paleosol, 15- Bk of Elm Creek paleosol, 16- Bk2 of Elm Creek paleosol, 17- CB horizon of Elm Creek paleosof,

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18- C horizon of Elm Creek paleosol, 19- top of Perez paleosol, 20- Perez paleosol, 21- Perez paleosol, 22- Perez paleosol, 23- CBk horizon of Perez paleosol, 24- bottom of Perez "C" just below (25 cm) gravel lens. 25- top of soil # 6, Bkl, 26- soil # 6, Bk2, 27- top of soil # 7, 28- "C" horizon of soil # 7('1), 29- top of soil # 8, "A" horizon, 30- bottom A soil # 8, above "C,", and 31- just below (10 cm) top of "C" soil # 8.

Samples were wet-screened through nested soil sieves (# 4, # 8, # 16, and # 30). Retained shell material was hand-picked from the resultant residue. Shells were identified to species and classified as adult or immature. [n the case of one species, Rabdotus mooreanus, four size classifications were identified: adult, adolescent, juvenile, and hatchling.

RESULTS

A total of 19 species was identified from the shell material extracted from the 32 samples. This molluscan assemblage consists of one pea clam, two freshwater mussels, one freshwater operculate gastropod, three freshwater pulmonate gastropods, one operculate terrestrial gastropod, and 11 terrestrial pulmonate gastropods. The species identified from the shell remains are listed and discussed in the next section.

Annotated List of Molluscan Species Recovered From 41 BX83 I Pisidium casertanum is probably the most widely distributed freshwater bivalve in the

world. This species is found in a great variety of freshwater habitats. Amblema pUcata is a medium-sized to large freshwater mussel that is found in

moderate-sized streams with flowing water and a firm substrate of either sand or gravel. Lampsilis teres is a freshwater mussel that is usually found in flowing water over sand

or fmn clay substrate. Oligyra orlJicuiata is the only temestrial operculate that occurs in the central Texas area.

This species is found in a wide variety of habitats that have a certain amount of cover material in the form of wood or rock. Substrate is usually calcareous in nature.

Cincinnatia cincinnatiensis is a small freshwater operculate gastropod that Was found in spring-fed streams with a firm substrate and shallow, slow current.

Physella virgata is a freshwater gastropod that is found in ponds and streams with slow-moving water

Gyraulus parvus is a small aquatic snail that is found in small spring pools and on aquatic vegetation in slow-moving water.

Helisoma anceps is a medium-sized aquatic snail that is found in stream-run streams over limestone gravel and cobble in the Texas Hill Country.

Pupoides a1bilabris is a small temestrial gastropod that is found in a variety of habitats with cover in the form of wood, rocks, or deep leaf litter.

Gastrocoptapellucida is found undercover objects in many types of habitats, generally rather open habitats with limited wood plant cover.

Gastrocopta procera is a small terrestrial gastropod that is often found in association with Gastrocopta pellucida, although G. procera requires more moisture than G. pelludda.

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Strobilops texasiana is another small terrestrial gastropod that is found in mesic microhabitats, often in subhumid habitats. This species is usually found under downed wood, usually associated with woody vegetation.

Sucdnea cf. solastra is an amber snail that is found in usually xeric microhabitats with periodic saturation of the soil. Habitat types include open woodland or brushlands and brushy savannahs. This species is known only from southern Texas and undoubtedly occurs in northeastern Mexico. It is apparently closely related to Succinea lureola, which is more widespread and usually more abundant Some workers would probably synonymize S. solastra under S. lureola.

Helicodiscus singleyanus is a small disc-shaped gastropod that is often found in the same microhabitats as the species of Gastrocopta listed above.

Deroceras laeve is a small gray to brownish slug that is found in protected habitats underneath rocks or downed wood, under which it may burrow to deeper soil layers with sufficient moisture. This species may also be found around the margins of wetlands-­marshes, ponds, or small streams--where it may actually enter the aquatic habitat to forage and absorb water.

Deroceras cf. aenigma is the designation given here to a series of slightly thickened, multi-layered slug plates that were recovered from the lower portion of this column. D. aenigma is a species known only from fossil slug plates that are preserved in Late Pleistocene and Early Holocene sediments, mostly in the southern Great Plains. Although nothing can be known directly about the preferred habitat of this species, its occurrence in the fossil record has generally been as part of a paleoassemblage that accumulated under cooler and/or moister conditions than are present today.

Euconulus folvus is a terrestrial gastropod that is common in many of the Late Pleistocene and Early Holocene molluscan paleoassemblages in the central portion of the United States. Living popUlations of this species are restricted to the northeastern United States as far south as the Appalachian Mountains with disjunct popUlations present in montane habitats of the Trans-Pecos Texas.

Rabdotus mooreanus is a large terrestrial gastropod that is found in open woodlands, savannahs, and prairies. This species is often found up on the vegetation during the hot periods of the year.

Polygyra texasiana is a medium-sized terrestrial gastropod that is found under rocks and downed wood in open woodlands, savannahs, and prairies.

PALEOENvmONMENTAL RECONSTRUCTION The molluscan shell remains extracted from the sediments of 4lBX831, as documented

in Table 3 and 4, demonstrate an overall homogeneity that belies the enviromental information that is present in the distribution of the species present. Below is a first attempt to reconstruct the paleoenvironment of 41 BX831 as demonstrated in the molluscan remains present in these sediments. These reconstructions are described in terms of the vegetational community type and structure. The resultant reconstructions are presented in temporal sequence from the oldest available time period to the modern soil. The breaks between vegetational types are somewhat arbitrary as any temporal variation in the environment will be gradual with very few punctuated environmental changes. Some of the inferred temporal boundaries are likely the result of the temporal distance between samples. Also, keep in mind that these reconstructions and the chosen boundaries are based solely on the molluscan remains. Although I believe that molluscan shell remains can provide very powerful information on the paleoenvironment of this region, these remains are--in the end result--<mly valid from the ecological perspective of the constituent molluscan species.

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Zone I-Marsh or Wet Grassland/Meadow-Samples 31 to 25 These lower levels are most remarkable in the limited number of species represented.

Indeed, except for a few, scattered fragments,of snail shell(some of which can be identified), the only molluscan remains present in these samples are slug plates of at least one, and likely two, species of gray slugs. The near absence of non-slug remains may be partially taphonomic as discussed in the next section of this report, but the analysis will be made assuming that the dominant molluscan life during the time period represented in these sediments was one or two species of slugs. Living populations of Deroceras laeve in this area are found concentrated under cover objects in seasonally moist microhabitats. This species may enter the margins of aquatic habitats. Deroceras aenigma is assumed to have lived in cooler and wetter climates than the present, but the details of the habitat have not been, and probably cannnot be, described for an extinct species. The restriction of slug plates referred to D. aenigma to the lower portions of this section may be an indication of cooler and moister microhabitats than in the upper portion of this section. The dominance of the assemblage by slugs indicates that a wet prairie or meadow could have been the likely vegetational community type. The absence of aquatic forms would indicate that this community was a "terrestrial" marsh, i. e., dominated by wetland grasses and sedges rather than a deeper wetland with emergent and submergent aquatic vegetation. However, if we assume that substantial amounts of terrestrial gastropod shell was dissolved, the same fate could have been met by freshwater gastropod and bivalve shells; any record of these aquatic habitats would have been lost. Seasonal loss of surface water is possible, even likely, but the substrate did not desiccate to the extent that is observed in temporary ponds of today. This zone includes all sediments assigned to soils 6, 7, and 8.

Zone 2-Savannah with Hooding Interludes-Samples 23-18 Several environmental conditions are indicated by the species represented in these

sediments. Significant beyond the mere presence of these species is also the size-class structure of some of the species. The abundance of Oligyra orbiculata indicates the presence of substantial amounts of woody vegetation, but the occurrence of Rabdotus mooreanus indicates the presence of open space between these woody plants. Most of the specimens of R. mooreanus are hatchlings, indicating that the oviposition and hatching niche of this species was well-represented, but that the area must have periodically become desiccated as indicated by the abundance of dead hatchlings and relative paucity of the more mature size classes. The presence of freshwater mussel shells and gastropod shells that appear to be flood debris indicates the occurrence of surface water at the site or a substantial alluvial input. The most likely vegetational community and general environment that meets these restrictions is an open savannah with scattered woody vegetation and substantial grass cover. The periodic moist conditions, often followed by rapid desiccation would seem to indicate the occurrence of periodic alluvial input with flood debris. Local precipitation would seem to be low to moderate and, possibly, seasonal in occurrence. This zone is roughly equivalent to the Perez Paleosol.

Zone 3-Mid-Grass Prairie (?)-Levels 18 to 8 Several gastropod species or groups of species indicate the occurrence of an open

habitat that had no great amoUilt of woody vegetation. Most of this section indicate conditions that were conducive to survival and reproduction of Rabdotus mooreanus. Levels without substantial R. mooreanus are those layers with aquatic snails, indicating alluvial input of flood debris, or the occurrence of many small-shelled species, indicating the occurrence of more continually moist soil conditions. The absence of O/igyro orbiculata from most of these levels indicates the rarity of woody plants. This zone seems to indicate the occurrence of low but dependable amounts of moisture. The plant community most likely to fit this description is a mid-grass prairie. However, the ability to

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paleoenvironmentally reconstruct a prairie setting will be discussed in the following section of this report. This wne of the column includes the Elm Creek Paleosol, the laminated wne, and the lower portion of the Medina Paleosol.

Zone 4-Mid-Grass Prairie with Surface Water-Levels 7 to 4 Presence of Rabdotus mooreanus and Helicodiscus singleyanus indicates the continued

existence of an open vegetational community. The presence of Pupoides albilabris and the near absence of Oligyra orbiculata indicate the occurrence of some cover object, probably wood, on the soil surface but the local absence of substantial amounts of woody plants. The occurrence of both fresh shells of Gyraulus parvus and Cincinnatia cincinnatiensis indicates the input of alluvium with flood debris shells or the likely local occurrence of surface water. The peak of flood debris shell input appears to be in level 6. The nature of this surface water is unclear, and may have included small streams or ponds, posssibly floodplain pools. The limited amount of burned shell fragments recovered during this study peaks and is almost restricted to this wne , indicating the likelihood of periodic fires that aid in maintenance of a mid-grass prairie. This zone includes the uppermost portion of the Medina Paleosol, the sandy wne, and the lower portion of the Leon Creek Paleosol.

Zone 5-Short- to Mid-Grass Savannah to Prairie-Levels 4 to I. The patterns of occurrence of most of ths snail species present indicate the continued

dominance of open grassland habitats. The occurrence of Oligyra orbiculata represents the return of woody vegetation to the site as an obvious, but possibly minor, portion of the plant community. Eroded and fresh shells of Gyraulus parvus and Cincinnatia cinci1l1UJliensis indicate the input of flood debris shells and the reduction of local surface water. Pupoides albilabris indicates the occurrence of downed wood in an area that is . generally dry, although the occurrence of periodically saturated soil conditions is not eliminated. This zone includes the middle and upper portions of the Leon Creek Paleosol and the modem surface soil, Venus clay loam.

DISCUSSION TOPICS The overall impression of the molluscan paleoassemblages recovered from the various

wnes of 41 BX83 1 is an indication of relative homogeneity on the species level. Although there exists enough variation in relative amounts of species to reconstruct different plant communities, the paleoassemblage in toto is one of a relatively few species with very little representation of extra1imital species. This species homogeneity is probably due to the lack of major change in the physiognomy of the site through the Late Pleistocene and Holocene. Postulated plant communities--be they marsh, meadow, grassland, or savannah--are all dominated by graminoid species with minimal to only moderate occurrence of woody species. This relative stability throughout a period with presumed significant variations in the ambient climate is a result of the relative importance of edaphic factors in relation to climatic factors in determining the basic structure of the plant community at this site with fine-grained, tightly packed soil.

Some variation in effective moisture that can be related to climate is indicated by the occurrence of two extralimital species. The aquatic gastropod, Cincinnatia cinci1l1UJliensis, was widespread during the Quaternary of Texas, although most localities are located to the north or east of Central Texas (Fullington, 1978). The slug, Deroceras aenigma, is pesumably an extinct species that lived in habitats similar to that of the modem Deroceras laeve, but habitat details are unavailable. Some native slug populations in the montane areas of western Texas have been assigned to this species in field and museum notes, but this specific designation has never been applied to any living population in a published report to date.

No shells of the terrestrial gastropod species that are present in the upper reaches of the

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Medina River and that are characteristic of the Balconian Biotic Province were recovered from these sediments. Not only were these species not living at this site during the Late Pleistocene and Holcene, shells of these species were not a recognizable component of the flood debris that was transported by high waters duing this time period. The lack of shift of the boundary of the Balconian terrestrial gastropods may not be typical of all faunal groups, however. Comprehensive investigations of several of the dominant faunal groups would be required to produced a definitive study of the spatial dynamics of this boundary through the Late Quaternary.

A significant proportion of the shells recovered from these sediments are not autochthonous to this site. Many of these shells were deposited as flood debris by ebbing flood waters. Most, if not all, of the Cincinnatia dncinnatiensis probably lived in a smaller spring-run stream upstream of this site. The single shell of Euconulus folvus is a mature shell that was secondarily deposited at this site. The biological origin of this shell was undoubtedly a protected woodland in a canyon in the upper reaches of the Medina River in the Texas Hill Country. This species has since been extirpated from Central Texas.

Charred shell remains were rare in the samples from 41 BX831. All remains were very fragmentary gastropod shells. Levels 2 and 19 contained charred fragments of Rabdotus mooreanus. Charred fragments of Polygyra texasiana and Oligyra orbiculata were recovered from samples 6 and 8, respectively. An unidentifiable fragment was recovered from sample 7. These few fragments may indicate the relative rarity of groundfires in this area, possibly due to lack of sufficient fuel load to carry a significant fire that would leave evidence in the form of charred shell.

The near lack of non-slug remains in the lowermost levels combined with the fragmentary, etched condition of the few gastropod shell remains in these levels raises the possibility of the occurrence of significant taphonomic changes of the original paleoassemblages that were merely a. sample of the original paleo fauna of this area. Molluscan shells are largely crystalline calcium carbonate with variable amounts of organic compounds present in the various layers. The most common crystalline form of calcium carbonate in terrestrial gastropods is aragonite, but the calcium carbonate in the slug plates is calcite (Evans, 1972:23). As calcite is more stable than aragonite (Chave, et al., 1962), in certain chemical environments, shells--even slug plates--that are composed of calcite could be expected to be differentially preserved, especially in older sediments where longer time periods have occcurred for dissolution.

The paleoreconstruction of prairie habitats as discussed above is somewhat problematical in my mind. I feel that there is a valid doubt that one can accurately postulate the occurrence of a prairie environment from terrestrial gastropods alone. In essence, my assumption of the existence of prairies at various zones of the column examined at 41BX831 is based on the lack of gastropods indicating the presence of woody plants. This "negative postulation" may not be inaccurate in its conclusions, but is not as sure or "clean" as the postulation of a woodland. A survey of living gastropods of several prairie remnants in Texas has revealed the occurrence of a very low species-diversity fauna that is characteristic of prairie sites (Neck, unpublished data). However, all of these species can be found in savannahs and open woodlands. Some species may also be found in the more exposed or well-drained portions of closed woodlands. The lack of terrestrial gastropod species that are endemic to prairie habitats is paralleled by most plant groups, including grasses, and many faunal groups, including vertebrates, and may relfect the relatively recent occurrence of broad expanses of prairie habitat.

SUMMARY STATEMENTS

The molluscan paleoassemblage extracted from the sediments of 4lBX83l indicate only small vegetational changes from those conditions that are observed today. However, the molluscan species recovered from an undated locality in alluvium of the San Antonio

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River near the current study site indicate some major changes in the general environment at some point upstream of this other locality. Seven species of terrestrial gastropods have been reported from San Antonio alluvium, two of which do not live in this region today. Whereas Gastrocopta annifera is found in protected areas of north central and Panhandle Texas (Fullington, pers. comm.; Neck, 1990), the other--Discus crokhitei--is not found living in eastern North America south of a line drawn from Kentucky to South Dakota (Hubricht, 1985: 107). However, western montane populations of D. cronkhitei are known as far south as the Guadalupe Mountains of Texas (Fullington, 1979).

The difference in the apparent environmental changes as demonstrated in these two paleoassemblages illustrates the complexity of analysis of the environmental changes in the past. Molluscan shells, indeed any biotic remains in sediments, are habitat proxies, not climate proxies. Certainly, climate is a major factor in the enviroment of any particular species, but many other factors impinge upon, and limit, the direct effect of the ambient climate on the occurrence and abundance of any particular species. To properly interpret the significance of the biotic remains in any site, one must understand the environmental limitations of each species and be able to recreate, mentally, the habitat and microenvironment in which the constituent species of the paleoassemblage live. Reconstruction involves vegetational community structure, soil texture and drainage, amount and nature of soil cover, and any other salient environmental factors that affect the dispersal and survival of any particular species in the paleoassemblage.

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LITERATURE CITED

Blair, W. Frank 1950 The Biotic Provinces of Texas. Texas Journal o/Science, 2(1):93-11

Chave, K. E., K. S. Defeyes, P. K. Weyl, R. M. Garrels, and M. E. Thompson. 1962 Observations on the Solubility of Skeletal Carbonates in Aqueous

Solutions. Science ,137(3523): 33-34. Durden, Christopher 1.

1974 Biomerization: An Ecologic Theory of Provincial Differentiation. In: Charles A. Ross (ed.), Paleogeographic Provinces ami Provinciality., pp. 18-53. Society of Economic Paleontologists & Mineralologists Special Publication 21.

Evans,John G. 1972 Land Snails in Archaeology. Seminar Press, London, 436 pp.

Fullington, Richard W. 1978 The Recent and Fossil Freshwater Gastropod Fauna of Texas. Unpublished

Ph. D. dissertation, North Texas State University, Denton, Texas, 279 pp. Fullington, Richard W.

1979 The Land and Freshwater Mollusca of the Guadalupe National Park, Texas. In:H. H. Genoways and R. J. Baker (eds.), Biological Investigations in the Guadalupe Mountains National Park. Texas, pp. 91-111. National Park Service Proceedings & Transactions Series, 4: 1-442, Wahington, D. C.

Gehlbach, Frederick R. 1991 The East-West Transition Zone of Terrestrial Vertebrates in Central Texas: A

Biogeographical Analysis. Texas Journal o/Science, 43(4):415-427. Hubricht, Leslie

1962 Land Snails from the Pleistocene of Southern Texas. Sterkiana, 7: 1-4. Hubricht, Leslie

1985.The Distributions of the Native Land Mollusks of the Eastern United States. FieldianaZoology (new series), 24:1-191.

Neck, Raymond W. 1983 Paleoenvironmental Significance of a Nonmarine Pleistocene Molluscan

Fauna from Southern Texas. Texas Journal 0/ Science. 35( I): 147-154. Neck, Raymond W.

1985 Paleoecological Implications of a Holocene Fossil Assemblage, Lower Rio Grande, Cameron County, Texas. Pearce-Sellards Series (Texas Memorial Museum),41:1-20.

Neck, Raymond W. 1987 Terrestrial Gastropod Succession in a Late Holocene Stream Deposit in

South Texas. Quaternary Research, 27(2):202-209. Neck, Raymond W.

1990 Ecological Analysis of the Living Molluscs of the Texas Panhandle.American Malacological Bulletin, 8(1):9-18.

Thylor, F. B., R. B. Hailey, and D. L. Diamond. 1966 Soil Survey of Bexar County, Texas. Soil Conservation Service and Texas

Agricultural Experiment Station. United States Government Printing Office. Washington, D. C., 126 pp. + 94 maps.

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Table I. List of Samples with Molluscs and Their Relationship to Stratigraphy at 41BX83 I.

Units StratName Location Sample Numbers

VITI modern soil surface 1m, If lower 2

VII Leon top 3 Creek middle 4 paleosol lower 5

sandy zone 6

VI Medina top 7 paleosol Bk 8-11

lower 12 CB I3

laminated zone 14

V Elm Bk 15 Creek Bk2 16 paleosol CB 17

C 18

N Perez top 19 paleosol 20-22

CBk 23 C (bottom) 24

III soil 6 Bkl 25 Bk2 26

II soil 7 top 27 C 28

I soil 8 A (top) 29 A (bottom) 30 C (top) 31

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Table 2. Molluscan Species Codes Used in Tables 3 and 4.

Freshwater Pea Clam

P c- Pisidium casertarmm

Freshwater Mussels

A p- Amblema plicaJa L t- Lampsilis teres

Freshwater Operculate Gastropod

C c- CincinnaJia cincinnaJiensis

Freshwater Pulmonate Gastropods

P v- Physella virgaJa G p- Gyraulus parvus H a- Helisoma anceps

Terrestrial Operculate Gastropod

00- Oligyra orbiculata

Terrestrial Pulmonate Gastropods

P a- Pupoides albilabris G pe- Gastrocopta pellucida G pr- Gastrocopta procera S t- Strobilops texasiana S s- Succinea solastra H s- Helicodiscus singleyanus D 1- Deroceras laeve D a- Deroceros cf. aenigma E f- Euconulus folvus R m- Rabdotus mooreanus P t- Polygyra texasiana

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Table 3. Distribution of Freshwater Molluscs Recovered From Column at 41 BX831 (see Table 2 for species codes).

Sample Number Species Codes

Pc Ap Lt Cc Pv Gp Ha

1m 1 If 2 1 I 3 1 2 4 2 3+5 5 1 5 4+6 6 2+6 4+ 11 7 1 3+1 8 1 3 5+1 9 1 \0 \1 12 13 *unidentifiable unionid fragments 14 0+ 1 I 15 16 17 18 2 1 19 2+0 2 20 21 0+1 22 23 24

I 25 26 27

I 28 29 30

l 31

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Table 4. Distribution of Terrestrial Gastropods Recovered From Column at 41BX831 (see Table 2 for Species Codes).

Sample Species Codes Number

00 Pa Gpe G pr SI S s Hs DI Da Rm Pt

1m 12+8 2 25+2 0+10 9+3 f+3+4+0 2 If 1 5+8 1 2+17 8 1+0+2+14 0+2 2 9+5 3+31 24+7 4+7+18+6 8+2 3 5 2+1 2+8 4+1 1+5+ 12+8 5+1 4* 3 1 1 1+16 2+4 12+7+21 +6 5 1+2 1+7 13 3+5+4+12 4+15 6 1 2+1 1 I 2+12 12+19 2+1+4+1 7 1+3 2 1+3 7+12 f+ I +4+0 0+1 8 f 2+ 11 3 1+3+1+1 2+3 9 1 0+5 1 2+3+1+0 2+1 10 1 0+1 2 2+3+1+0 1 11 1 1 3+1+0+0 1 12 1+6 1 6+5+3+5 1 13 1 3+7+3+ \ 0+1 14 2+1 0+1 5+2 1+2+5+3 0+1 15 1+4+3+0 5+2 16 f 17 1 1+1 2+4+2+0 18 0+\ 0+1 \9 1 0+2 4+3+0+0 20 3 f+4+5+22 \+4 21 5 5+5+8+23 22 4 4+2+8+19 2+5 23 5 0+3 2+4+6+\9 2+3 24 \ f 25 4 tl

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26 27 f 28 f 29 f 30 f 31

2

7 6

t! f

f f f

* one secondarily deposited shell of Euconulusfulvus- E f-recovered from this level.

f f

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LATE PLEISTOCENE AND EARLY HOLOCENE REGIONAL LAND USE PATTERNS: A PERSPECTIVE FROM THE PRELIMINARY RESULTS OF

ARCHAEOLOGICAL STUDIES AT THE RICHARD BEENE SITE, 41BX831, LOWER MEDINA RIVER, SOUTH TEXAS

Alston V. Thoms

Department of Anthrop01ogy, Texas A&M University, College Station, Texas 77843-4352 U.S.A.

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2

ABSTRACT

The Richard Beene archaeological site (4IBX831) is located about 25 Ian south of San Antonio on the edge of the first terrace above the Medina River. Its most salient ecological characteristics are its riverine location and its ecotone setting near the Tamulipan, Balconian and Texan Biotic Provinces. Previous archaeological studies in this broad ecotone demonstrate that hunter-gatherers continuously occupied the region throughout the last 11,200 years, and perhaps during pre-Clovis times as well. Excavations at the Richard Beene site yielded well-stratified artifacts, features, faunal and floral remains from the Late Paleoindian through Late Prehistoric periods in the upper 12 m of terrace alluvium at the proposed dam site for Applewhite Reservoir. About 20 stratigraphically distinct archaeological deposits were recognized. Depositional processes seem to account for much of the intrasite variation in preservation conditions.

Two Late Paleoindian occupation zones (ca. 8,800 B.P.) yielded what is probably one of the largest Angostura assemblages in North America. The extensively excavated Early Archaic occupation surface (ca. 7,000 B.P.) has many well-preserved features, associated projectile points, other artifacts, and faunal remains. Middle Archaic surfaces (ca. 4,100-4,500 B.P.) were comparatively feature-rich and artifact-poor. One of the Late Archaic occupation zones (ca. 3,000 B.P.) has a large, earth oven-like feature, as well as a relatively high density of broad blade projectile points and thin bifaces. The Late Prehistoric (ca. 1,000-400 B.P.) component did not have intact features, but arrow points and ceramic fragments were recovered.

Use of local river gravels as raw material for stone tools and the basic approaches to tool manufacturing appear to have changed little during the 9,000 years of intennittent occupation. Only the Late Paleoindian component has a high diversity of tools types, but it also has the largest artifact sample. Overall, there is considerable inter-component variation in the density of chipped stone artifacts, fire-cracked rock, and mussel shells, suggesting variation in the nature and intensity of occupation. The site's archaeological record provides a uniquely long-term perspective on the use of a riverine locality along the ecotone between the central Texas plateau prairie and the south Texas plains.

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3

INTRODUCTION

The Archaeological Research Laboratory at Texas A&M University is conducting a multidisciplinary research project that focuses on the Richard Beene archaeological site (41BX831), located about 25 km south of San Antonio on the edge of the first terrace of the Medina River (Figures 1 and 2a). Our investigations are pan of the larger Applewhite Reservoir archaeological project undertaken to mitigate adverse effects that construction of Applewhite Reservoir would have on archaeological and historical sites included in or eligible for the National Register of Historic Places. The project is funded by the San Antonio City Water Board pursuant the "Programmatic Agreement" among the Fort Worth District Corps of Engineers, the Advisory Council on Historic Preservation, the Texas State Historic Preservation Officer, and the San Antonio City Water Board (Advisory Council on Historic Preservation, 1990).

Upon discovery by a team of Texas A&M archaeologists in 1989, the site was designated 4IBX831, but we subsequently named it in recognition of Richard Beene, the chief inspector for Freese and Nichols, Inc., the engineering company that designed the Applewhite Reservoir construction project. Mr. Beene discovered an extensive Early Archaic component that had been exposed by heavy machinery 6.5 m below surface in the deep trench being dug for the darn (Figure 2b). He reported his discovery to us as we were fInishing our work at the site's previously identifIed Middle Archaic component and preparing to· begin excavations at a nearby site where we anticipated finding Early Archaic deposits. Had Mr. Beene waited half an hour to make his report, the pan scrapers would have obliterated the Early Archaic component, and we would not have leamed nearly as much about that time period. We might not have discovered the site's Late Paleoindian components at all.

Artifacts and features representing archaeological cultures from the Late Paleoindian through the Late Prehistoric periods are well-stratified in the upper 12 m of terrace alluvium at the proposed darn site for Applewhite Reservoir. Dozens of depositional units and four paleosols encompass at least 20 discrete archaeological deposits spanning the last 9,000 years or more. The well-stratifIed sediments between 12 and 16 m below surface contain faunal remains that date between 11,000 and 14,000 B.P. (C-14 ages from soil humates), but as yet no definite cultural material have been recovered from these Late Pleistocene deposits.

Discovery and excavation of the Richard Beene site afforded the opportunity to address research topics pertinent to human adaptations and site fonnation processes in the sub-humid savannas of North America during the Late Pleistocene and Holocene periods. These topics include soil fonnation processes, geomorphology, chronostratigraphy, and paleoenvironments (see Mandel and Jacob, this volume), palynology, paleobotany, and paleoenvironments (see Dering and Bryant, this volume), gastropod assemblages and

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Figure 1.

41BXB31 Richard Bun.

o 110 /OQ ,~o I~

--=~~=~_..;;~~ IIllt'

PHYSIOGRAPHY

Physiographic map of Texas and vicinity showing the location of Bexar County, the Richard Beene site (41BX831), and the surrounding physiographic regions (redrawn from Arbingast et al., 1976:8).

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Figure 2.

)

a: Photograph of the Richard Beene site prior to excavation; site area extends along the treeline and adjacent terrace surface; view to the north; b: photograph of the Richard Beene site at the time Mr. Beene discovered the extensive Early Archaic surface in the dam trench; view to the north.

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paleoenvironments (see Neck, this volume), as well as faunal assemblages, taphonomy, and paleoenvironments (see Baker and Steele, this volume).

4

This chapter presents some of the preliminary results of the archaeological studies at the Richard Beene site. The first part of the chapter begins with a discussion about the site's ecotonal setting to provide an environmental framework for the regional archaeological records. Next comes a review of the archaeology of the northern part of south Texas and the adjacent southern portion of central Texas. Included is a preliminary land use model for the lower Medina River valley. The second part of the chapter focuses on a preliminary description of the archaeological assemblages at the site, especially those from the more extensively excavated components. Also included is a discussion of site formation processes and an intersite comparison of components. It must be emphasized, however, that this information comes from the very preliminary results of our initial analyses. Further analyses will undoubtedly lead to changes in·the descriptive results and preliminary interpretations presented herein.

AN ECOLOGICAL CONTEXT

From a broad regional or macroenvironmental perspective, the setting of the Richard Beene site and its surrounding environs for more than 150 krn is one of a modified humid subtropical climate and savanna vegetation (Arbingast et al.,1976:8-13; Black and McGraw 1985:46; Blair, 1950:Figure I, 100-103, 112-113)). Within this expansive landscape, however, there is considerable variation in physiographic regions, soils areas, and biotic provinces. In fact, the most salient ecological characteristic of the site area and vicinity may well be its ecotonal setting wherein species diversity is usually greater compared to the interior parts of biotic zones (cf. Butzer, 1982; Odem, 1971). This, in combination with a riverine setting, suggests that 4IBX831 is situated in a comparatively food-rich zone. Hester (1989:123) recognized the relatively high productivity potential of similar riverine settings when he referred to riparian forests in the upper (i.e, northern) part of south Texas as "high density resource zones."

Three major physiographic regions that roughly coincide with "soil areas" converge in Bexar County (Figure 1): (1) the Edwards Plateau (and Balcones Escarpment), to the north and northwest of 4IBX831; (2) the Blackland Prairie, to the north and northeast of the site; and (3) the Texas Gulf Coast Plain (i.e., the Rio Grande Plain soil zone) that encompasses the site and areas to the south, west and east (Arbingast et al.,1976:8,12; Black and McGraw 1985:42). Modem vegetation regions in the site's macroenvironment are as follows: (1) juniper-oak-mesquite savanna on the Edwards Plateau; (2) bunch and short grasses on the Blackland Prairie; and (3) a combination of mesquite-chaparral savanna and oak-hickory forest on adjacent parts of the Gulf Coastal Plain (Arbingast et al., 1976: 13). This suggests that people who occupied the Richard Beene site would have had reasonable access to a wide variety of resources.

)

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5

The distribution of biotic provinces in the site's mesoenvironmental zone, an area within 30 km or so of 41BX831 that could be exploited regularly by site's inhabitants, also exemplifies the ecotonal setting. The boundaries of three biotic provinces intersect in or very near Bexar County, Texas (Blair 1950:Figure I). The Richard Beene site is within the Tamulipan Biotic Province, albeit at or near its northernmost limits. This province extends far to the south of the lower Medina River valley, and it coincides roughly with Texas' Rio Grande Plain soil zone (Arbingast et al., 1976:12). It has a semiarid, megathermal climate, enabling plant growth throughout the year that supports a wide range of vertebrate fauna including Neotropical, grassland, and basin desert species (Blair, 1950:103).

The Balconian Biotic Province, to the. west and northwest of the site area, falls largely within the Edwards Plateau physiographic region (Blair 1950:112-114). It has a dry, subhumid, mesothermal climate that supports savanna vegetation. A variety of animals characteristic of desert basin habitats and hardwood and pine forests occupy this province, as do some grassland and Neotropical species.

To the northeast of the site is the Texan Biotic Province that encompasses the Blackland Prairie physiographic region and others to the east The moist subhumid climate supports both grasslands and hardwood forests, and occasional stands of pines that in turn support a variety of vertebrate grassland and forest species (Blair 1950: 100-101). Baker and Steele (this volume), Black and McGraw (1985), and McGraw and Hindes (1987) provide more detailed information on the available fauna in the site area and vicinity.

The riverine setting of the site's microenvironment (site catchment), the ~a within a few kilometers that could be easily exploited, provided ready access to aquatic, riparian, and upland resources. Aquatic fauna include fish, shellfish, and turtles. Riparian forest vegetation, including pecan, oaks, sycamore, cypress, elm, cottonwood, hackberry, and mulberry, dominates the bottomland adjacent to the Richard Beene site. Prior to farming, the terrace where the site is located (Tl' see Mandel and Jacob, this volume) was probably a mesquite-oak savanna, whereas the surrounding higher terraces (Le., Tz and T" see Mandel and Jacob, this volume) and uplands were probably more of an oak savanna (Blair, 1950: 103; McGraw and Hindes, 1987:22-39; Neck, 1991; Robbins, 1991a, 1991b; also see Dering and Bryant, this volume).

Given the site's ecotonal setting, it would have afforded ready access to ethnographically important food resources, including white-tailed deer, pronghorn, bison, bear, turkey, fish, shellfish, nuts, berries, prickly pear, mesquite beans, and wild root foods (Campbell, 1975). Historical accounts clearly indicate that game--deer, bison, pronghorn, bear, and turkey--and nut foods, notably pecans and acorns, were usually plentiful along the stretch of the Medina River where the Richard Beene site is located (Neck, 1991; Robbins, 1991a, 199Ib).

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For much of south Texas, however, previously available paleoenvironmental data have been interpreted as indicating that a "mosaic vegetational pattern probably was well established throughout the post-glacial period and perhaps even longer" (Bryant and Holloway, 39:39; also see Dering and Bryant, this volume). While climatic changes may have affected the nature and distribution of food resources in the uplands around the Richard Beene site, the riverine and near-river resources may not have been affected appreciably during the last 10,000 years or so.

6

Little is known about the effects of local and regional edaphic conditions (or other factors) on "advances and retreats" of biotic provinces in the vicinity of the site (cf. Bryant and Holloway, 1985). It seems plausible, however, that even in the surrounding uplands the general structure of food resources available within a few kilometers of the Richard Beene site may have been similar throughout the Holocene and Late Pleistocene. In any case, preliminary results of paleoenvironmental studies for the Applewhite Reservoir archaeological project fail to provide evidence for dramatic changes during the last 10,000 years in the depositional environment. It is important to emphasize, however, that the data are preliminary. More complete analyses may yet demonstrate that significant environmental changes occurred during the terminal Pleistocene and Holocene periods that would have altered the structure of available food resources.

AN ARCHAEOLOGICAL CULTURE CONTEXT

Archaeology in the eastern section of the Edwards Plateau, the southern part of the Blackland Prairie, and the adjacent areas of the Gulf Coast Plains is now fairly well known. The existing data base comes mainly from federally mandated cultural resources studies conducted during the last 10-15 years. Results of these and earlier studies demonstrate that hunter-gatherers continuously occupied the regions encompassing and surrounding the Richard Beene site throughout the last 11,500 years, and there is some evidence for pre-Clovis period utilization of the landscape (Black, 1989a, 1989b; Hester 1989).

The Archaeological Record Beyond the lower Medina River

Survey and excavation work carried out in the lower Nueces River valley in conjunction with the construction of Choke Canyon Reservoir (ca. 85 krn south-southeast of 4lBX831, on the Frio River near its confluence with the Nueces River, Figure 1) revealed a long history of hunter-gatherer land use on the south Texas Plains (Hall, Hester, and Black, 1986: 394-406). A variety of Paleoindian projectile point types, including Plainview. Golondrina. Angostura, and Scottsbluff. were surface-collected from sites located on high terrace remnants, and local residents reported finding Folsom and Clovis points on similar landforms. Buried Early Archaic components were identified at

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)

)

7

two sites (41LK31/32 and 41LK(1) where charcoal from fire-cracked rock features yielded radiocarbon ages ranging from 6,360 ± 90 yr B.P. (TX-4690) to 4,690 ± 80 yr B.P. (TX-2921). A stemmed, Bandy point, considered to be representative of the Early Archaic period, was recovered from 41LKSI (Hall, Hester, and Black, 1986:96, 397, 585). Other sites yielded projectile points characteristic of the Early Archaic period, but in general, the Middle and Late Archaic periods and the Late Prehistoric period were better represented than the earlier period sites (Hall, Hester, and Black, 1986).

Archaeological investigations in the upper Salado Creek basin of northern Bexar County (ca. 35 km north of the Richard Beene site) also reveal a long history of hunter­gatherer land use (Figure 1). Radiocarbon ages from the Panther Springs Creek Site (41BX228), located along the Balcones Fault Zone that forms the boundary between the Edwards Plateau and the Blackland Prairie, indicate that especially intensive occupation occurred between 5,500 and 1,000 B.P.; some of projectile point types are suggestive of occupation several thousand years earlier as well (Black and McGraw, 1985). Other excavated sites in the upper Salado Creek basin yielded Clovis. Folsom. and Plainview points indicating occupation during the Early Paleoindian period (ca. 11,200-10,000 B.P.), as well as Golondrina and Angostura points characteristic of the Late Paleoindian period (ca. 10,000-8,000 B.P.). Projectile points considered representative of the entire Archaic period (ca. 8,000-1,200 B.P.) and the Late Prehistoric period also are found at many of the sites (Hester 1977; McGraw, 1985a:302-326).

In addition to projectile points, other diagnostic Clovis materials including, cores, blades, core tablets, and tools made on blades (as well as some Folsom material) come from 41BX52, one of the upper Salado Creek basin sites. These materials were excavated from a stratum separated from overlying cultural deposits by a sterile stratigraphic unit (Frison, Henderson, and Goode, 1991). Another site in the Salado Creek basin, the St. Mary's Hall site (4lBX229), contained a substantial Plainview occupation. Numerous Plainview points were excavated, along with a variety of blanks/cores, a core-chopper, large bifacial preforms in various stages of reduction, a bifacial Clear Fork tool, a large uniface, and several edge modified tools (Hester, 1991a; Hester and Knepper, 1991).

Recent excavations and ongoing analysis of materials from the deeply buried, stratified, multi-component Wilson-Leonard site (41WM235), located in the prairie zone some 180 km northeast of the Richard Beene site, also indicate extensive use of the regional landscape prior to 8,000 years ago (Weir 1985; Michael Collins, personnel communication, 1992). Kincaid Rockshelter in the western part of south Texas (ca. 150 km west of 4lBX831) produced Paleoindian cultural materials, including several varieties of Angostura points (Collins, Evans, and Campbell, 1988; Collins, personnel communication, 1992). Collectively, the widespread occurrence of fluted and lancelot projectile points in Bexar County and surrounding regions provides ample evidence for substantial human occupation of the region during the Late Pleistocene and Early Holocene (Hester, 1977; Largent, Waters, and Carlson, 1991; Meltzer, 1986).

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There is some evidence for pre-Clovis occupation in South Texas, as there is for other parts of the Americas (Fagan, 1992: 240-244; Hester, 1989). Two zones with cultural materials at Cueva Quebrada on the Rio Grande produced radiocarbon ages ranging from about 14,300 to 12,300 B.P.; both zones yielded chipped stone artifacts, and the lower one contained the remains of extinct fauna (Collins, 1976, personnel communication, 1992). Hester (1989:121) also discusses two other places in the Gulf Coast Plains as potential pre-Clovis candidates:. (I) Berger Bluff site (41GD30), located more than 150 kin southeast of the Richard Beene site, yielded chipped stone artifacts associated with an "unprepared, fired surface," termed a "small hearth," and an adjacent deposit of "microfauna," radiocarbon ages from charcoal in these deposits ranged from about 11,550 to 7,700 B.P. (Brown. 1987); and (2) a fossil locality on Petronila Creek (located more than 150 kin south-southeast of the Richard Beene site, near the mouth of the Nueces) where C.R. Lewis, a geologist, has been excavating mammoth bones, some of which he believes may have been modified by people. My objective in mentioning these sites is not to debate their authenticity; rather, it is to recognize the potential for pre­Clovis human occupations in south-central Texas in general, and the lower Medina River valley in particular.

The Archaeological Record in the Applewhite Reservoir Area

Archaeological survey and testing work conducted in 1981 and 1984 for the . I proposed Applewhite Reservoir identified dozens of prehistoric sites, most of which were assigned to the Early, Middle, or Late Archaic periods (McGraw and Hindes, 1987). Late Prehistoric sites were recorded, but their frequency was comparatively low. Early Archaic features and tools were unusually common, and included large fire-cracked rock features. Guadalupe tools and Martindale points. Several lancelot projectile points reminiscent of Paleoindian types were surface-collected, but it was postulated that "the diverse riparian resource zones within the drainage basin areas may have been less significant than the broad savanna adjacent to or south of the study area, which contained the forage necessary large groups of herd animals" (McGraw and Hindes, 1987:364). It was also recognized that sites dating to this period might have been removed by scouring or buried deeply in the older terraces.

Subsequent archaeological and paleoenvironmental investigations in 1989 and 1990 demonstrated that indeed sites and paleosols were buried deeply in the Medina River valley (Archeological Research Laboratory, 1991; Carlson et aI" 1990). Five paleosols were identified in the upper 15 m of terrace alluvium and in alluvial fan deposits; bulk sediment samples yielded radiocarbon ages for the paleosols ranging from about 11,200 to 1,600 B.P. These data demonstrated the potential for Paleoindian sites to be well preserved in the reservoir area. Additional survey work resulted in the discovery of several new sites. More than 20 sites were test excavated, and yielded cultural materials representative of the Late Paleoindian, Early, Middle, and Late Archaic, and Late

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Prehistoric periods. Radiocarbon assays on charcoal and soil humates from these sites yielded ages from about 8,400 to 800 B.P.

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Site 41BX831--later named the Richard Beene site--was one of those discovered during the new survey work. Backhoe and test pit excavations led to the identification of three components at the site. The Middle Archaic component (2.6 m below surface) yielded a radiocarbon age of 4,570 ± 70 yr B.P. (Beta 38700) and an oven-like feature in the Late Archaic component (1.25 m below surface) dated to 3,090 ± 70 yr B.P. (Beta-36702; these and all subsequent dates with lab numbers are C-13 adjusted). In the absence of radiocarbon ages or temporally diagnostic artifacts, the cultural materials in the upper 30 cm of the site were presumed to be Late Prehistoric in age (Archeological Research Laboratory, 1991:111-117; Carlson et al., 1990).

Patterns in the Inter-Regional Archaeological Records

In reviewing the prehistory of the south Texas Plains, Black (1989b:61) recognized that the portion of the south Texas Gulf Coastal Plain north and east of the Frio River seems "to be more closely linked to central Texas than we previously realized." Hester (1989:121) has also recognized broad similarities in the archaeological records for south and central Texas, as well as for the adjacent parts of the lower Pecos River canyonlands. Table 1 summarizes information compiled by Black (1989a, 1989b) for the major prehistoric cultural periods in south and central Texas. For a description of the various projectile point and tool types noted in Table 1 and elsewhere in the text, the reader is referred to Turner and Hester's (1985) A Field Guide to Stone Artifacts of Texas Indians.

In his synthesis of south and central Texas, and the adjacent lower Pecos River canyonlands, Hester (1989:121) identified several "adaptation types ... as abstractions designed to suggest broad cultural-ecological patterns." Four of those potentially pertain to the archaeology of the Richard Beene site and surrounding environs: (1) Pleistocene foragers and hunters; (2) specialized hunters; (3) Holocene foragers and hunters; and (4) specialized plant collectors.

Hester's (1989) "Pleistocene foragers and hunters" adaptation type dates to before 11,200 B.P. It is a hypothetical pre-Clovis construct wherein generalized hunting and gathering activities predominate and specialized big game hunting is of lesser importance. As noted earlier in this discussion, two south Texas sites, Berger Bluff (Brown, 1987) and Cueva Quebrada (Collins 1976), as well as the Petronila Creek fossil locality are "potential candidates" for this adaptation type.

"Specialized hunters" of big game animals, including mammoth, now extinct and modem bison, operated in the northern part of the south Texas plains and adjacent regions at various times in the past. This pattern was especially evident when bison densities

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Table 1. Selected Characteristics of Archaeological Cultures in southern Central and northern South Texas; Data Summarized from Black's (1989a, 1989b) Review of the Central Texas Plateau Prairie and the South Texas Plains.

TIME PERIODS CENTRAL TEXAS SOUTH TEXAS

PALEOINDIAN Diagnostics: Early (pre-lO,OOO B.P.): Clovis, Diagnostics: Early: Clovis. Folsom, Plainview; Folsom, Plainview; Late: Golondrina. Late: Golondrina, & Angostura points; finely

Cen. TX, 11 ,200- Angostura, Scottsbluff. Meserve. also some flaked end scrapers on blades, bifacial Clear Fork 8,000 B.P. forms of stemmed and barbed points tools

("Transitional Population/Site Density: very low, few are Population/Site Density: low, sites uncommon, Period:" 9,000- intact (e.g.,Wilson-Leonard) except on Nueces-Guadalupe Plain

7,000 B.P.) Site Locations: too few sites to detect patterns Site Locations: high terrace, uplands, buried in Subsistence: Early: now-extinct big game valley alluvium

Sou. TX, 11 ,200- (e.g., mammoth and bison); Late: fully Archaic Subsistence: Early: big game; Late: generalized 8,000 B.P. lifeway (i.e., deer, small game, river mussels) Other: small bands, with extremely large

Other: small bands, nomadic hunters territories

EARLY Diagnostics: Martindale. Uvalde. Gower. Bell, Diagnostics: Andice, Bell. Bandy. Martindale, ARCHAIC Nolan, Bulverde points, Guadalupe and Uvalde (early expanding stems), Early Triangular,

unifacial Clear Fork tools Guadalupe and unifacial Clear Fork tools Cen. TX, 8,000- Population/Site Density: low, more sites than Population/Site Density: low, sites are generally

5,000 B.P. during previous period uncommon (" Transitional Site Locations: concentration along Balcones Site Locations: high terraces, upland locations, Period:" 9,000- Escarpment buried in valley alluvium

7,000 B.P.) Subsistence: large technological inventory of Subsistence: river mussels, snails, turtle, fish unspecialized tools suggests a wide range of [presumably deer too?]

Sou. TX, 8,000- resources Other: small bands, extremely large territories 4,500 B.P. Other: small, highly mobile bands

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Table 1. Selected Characteristics of Archaeological Cultures in southern Central and northern South Texas; Data Summarized from Black's (1989a, 1989b) Review of the Central Texas Plateau Prairie and the South Texas Plains.

TIME PERIODS CENTRAL TEXAS SOUTH TEXAS

MIDDLE Diagnostics: Early: Nolan and Travis; Late: Diagnostics: Pedernales. Langtry, Kinney, ARCHAIC Pedernales. Langtry. and Marshall, Bulverde Bulverde, Lange, Morhiss. Tortugas, medium to

throughout small distally beveled tools Cen. TX, 5,000- Population/Site Density: populations higher Population/Site Density: population growth, sites 3,000 B.P. (some argue highest of all), many more sites more common

than earlier Site Locations: upland, alluvial, and tributary Sou. TX, 4,500- Site Locations: very widespread, especially settings

2,400 B.P. burned rock midden sites Subsistence: reliance on plants (acorns and Subsistence: deer most important, but nuts mesquite beans), deer, snails, river mussels, other (acorns) very important, also yucca and river animals mussels Other: roasting hearths, more restricted territories, Other: appearance of bumed rock middens; cemeteries "primary forest efficiency"

LATEffERMI· Diagnostics: Late: Mantell, Castroville, Marcos Diagnostics: Ensor, Frio. MaICos, Fairland. Ellis. NALARCHAIC (broad triangular blades); Terminal: Ensor. small distally beveled tools, Nueces scrapers,

Frio, Darl. Fairland (small expanding stems) corner-tang knives Cen. TX, 3,000- Population/Site Density: population density Population/Site Density: population higher than

1,200 B.P. high (some argue highest of all in Terminal before, sites very common Archaic), more sites in Terminal Archaic than Site Locations: virtually all topographic settings

LATE ARCHAIC earlier Subsistence: focused on plants and small animals Site Locations: more sites in riverine settings (rodents and rabbits), [presumably deer too?]

Sou. TX, 2,400- (?) Other: roasting features more common and more 1,200 B.P. Subsistence: less specialized; bison and deer carefully constructed, trade evident, predicting

hunting & more plant resources, fewer burned territorially focused cemeteries rock middens Other: trading evident, more cemeteries

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Table 1. Selected Characteristics of Archaeological Cultures in southern Central and northern South Texas; Data Summarized from Black's (1989a, 1989b) Review of the Central Texas Plateau Prairie and the South Texas Plains.

TIME PERIODS CENTRAL TEXAS SOUTH TEXAS

LATE Diagnostics: Austin: Scallorn arrow points and Diagnostics: Austin: Scallorn, Edwards. Fresno. PREHISTORIC other expanding stem forms; Toyah: Perdiz Padre points; Toyah: Perdiz, beveled knives, small

arrow points and pottery, also beveled knives end scrapers; pottery throughout Cen. TX, 1,200- and small end scrapers Population/Site Density: fairly high populations,

400 B.P. Population/Site Density: population decline sites very common during Austin, possibly major population Site Locations: primarily confined to water-

Sou. TX, 1,200- movements proximate locations, upland sites less common 400 B.P. Site Locations: increased use of rock shelters Subsistence: (best preservation) emphasis on

Subsistence: deer most important throughout, faunal exploitation, deer most common, bison, & but bison too during Toyah and perhaps limited pronghorn, along with an extraordinarily wide agriculture range of species Other: interaction with Caddo populations to Other: rapid culture change, widespread north and east; intergroup conflict during (interregional, Central and South Texas, and Austin phase; reintroduction of blade beyond) similarities, influences from southern technology during Toyah interval plains

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were comparatively high during parts of the late Holocene period (Hester, 1989). Groups representative of this adaptation type are believed to have relied heavily on broad spectrum hunting and gathering, while taking advantage of increased numbers of big game. This type of adaptation is represented by several archaeological cultures: (1) Early Paleoindian period, 11,200-10,00 B.P.; (2) part of the Late Archaic period, ca. 2,800 B.P.; and (3) during the last part of the Late Prehistoric period, 600 and 400 B.P.

In the northern part of the south Texas plains, the "Holocene foragers and hunters" adaptation type occurred during the Late Paleoindian period, during most of the Early, Middle, and Late Archaic periods, and for all but 200 years of the Late Prehistoric period. Hester argues that the modem environment developed during the middle and late Holocene, and it was then that "high density resource zones" such as riparian forests began to play important roles in regional land use systems. Holocene foragers and hunters utilized "practically all available plant and animal species," including deer, but snakes and other reptiles, rabbits, other small game, fish, river mussels, berries, and other plant foods are believed to have been especially important (Hester, 1989: 122-123).

Hester (1989:123-124) applied the "specialized plant collector" adaptation type only to central Texas. It began as early as 5,000 B.P. and is represented mainly by burned rock middens. He argues that the consensus opinion is that these features represent the remains of repeatedly used earth ovens, and that the burned rock and ashy soil is related to leaching tannic acids from acorns or perhaps other nut foods. Deer and river mussels also were important food resources to specialized plant collectors, but "specialized nut harvesting and processing was the main character of this adaptation type" (Hester 1989:124).

Features resembling the central Texas burned rock middens have been reported from sites in the Choke Canyon Reservoir area as well. There too, the consensus opinion, albeit "stretching the inference very thin" was that the features may have been related to processing acorns (Hall, Hester, and Black, 1986:401). An alternative speculation was that the large "heat-fracture sandstone hearth features" at one of the sites (41MC209) may have been used to process other plant foods, perhaps mesquite beans, prickly pears, or yucca (Thoms, Montgomery, Portnoy, 1981: 187-196). In any case, there continues to be considerable discussion on the function of burned rock middens (Hester, 1991 b).

Burned rock features, including circular concentrations up to 5 m in diameter and linear clusters more than 2 m in length, were the most common feature type observed during the initial survey and testing work for Applewhite Reservoir (McGraw and Hindes 1987). Based on their spatial association with temporally diagnostic artifacts, some of these features were considered to be Early Archaic in age. Although these features were not considered to be morphologically similar to central Texas burned rock middens, McGraw and Hindes (1987:365-364) recommended comparing them to similar features within and adjacent to the Balcones Escarpment. A large burned rock feature was

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excavated (1.25 m below surface) at one of the sites (4IBX793) recorded and tested during subsequent investigations. It covered least 4 m2 and charcoal associated with it yielded a radiocarbon age of 3,880 + 50 yr B.P. (SMU 2327; C-13 adjusted) (Archeological Research Laboratory, 1991:1,9-110).

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The function of the fIre-cracked rock features in the Applewhite Reservoir remains to be detennined, as does the relationship between these features and the better known burned rock middens of central Texas. It seems likely, however, that procurement and processing of plant foods, including nuts and roots, must have been an important component of some past land use systems in the lower Medina River Valley. If the large fIre-cracked rock features are indicative of plant food processing activities, and to the extent they become a component of the regional archaeological record by 5,000-4,000 B.P., their presence in the regional archaeological record would be consistent with a broader pattern.

In North America and elsewhere in the world, archaeological evidence for the intensive use of plant food resources becomes apparent during the latter part of the early Holocene and the mid-Holocene (Cohen, 1977; Fagan, 1992). In parts of west Texas, the PacifIc Northwest, and as far away as southern Africa, bulk procurement and processing of root foods is an indication of intensifIed land use that can be detected archaeologically by the presence of large rock-filled or rockless earth ovens (Thoms, 1989).

A Preliminary Land Use Model

In this part of the chapter, I present a preliminary land use model for lower Medina River valley and surrounding environs. The model draws selectively from the information summarized in the preceding pages and from broad patterns in prehistory. It is a speculative synthesis of the regional archaeology that is developed from the perspective of long-term land use intensification. It also serves as a general working model for the Applewhite Reservoir archaeological project that will be refIned into a more testable version as our analyses continue.

As originally developed, the project's research design focused on changes in site strucrure and mobility strategies over time, and, at least in part, in response to environmental change (Carlson et al., 1990). What we are learning now from the preliminary results of our paleoenvironmental analyses, suggests that, when viewed from the perspective of the floodplain/terrace setting for 4IBX831, there may not be much in the way of microenvironmental (i.e., site catchment area) change. There may well have been significant environmental change, however, in the mesoenvironmental and macroenvironmenal wnes that remains undetected in a riverine setting.

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From the perspective of the working research design, we are interested in evidence about land use intensification or any other kind of land use change during the late Pleistocene and Holocene periods. To the extent that such evidence can be identified in the archaeological record, we want to model how and why the changes occurred. Much of our research focuses on the role of paleoenvironmental change in conditioning land use change, but we also want to assess the roles of population growth/packing and other potential "prime movers," as well as changes in the character of the immediate site environment, such as from a floodplain to a terrace setting.

The project area and vicinity (Le., the San Antonio River basin) serves as a case study, but available data from the adjacent Nueces River basin to the south and the Colorado and Brazos River basins to the north will be used to develop a regional context. Subhumid, subtropical climatic ecosystems and floodplain settings constitute the broader spatial context into which the data we generate will be placed for comparative pwposes.

By land use, I mean the patterned exploitation of resources by human groups, the manner in which they used places on the landscape, the technologies they employed in the process, and the effect of that exploitation on the ecosystem (cf. Kirch, 1982). By intensification, I mean a general (i.e. nomothetic) trend through the millennia toward the expenditure of more energy per unit area to recover more food from the same landscape to feed more people (cf. Cohen, 1977; Johnson and Earle, 1987). The working model presented here holds that a negative imbalance, typically too many people for the available commonly-used food resources, places stress on an existing land use system, and thus, forces intensification.

The model is intended to specify general trends that are detectable in the local and regional archeological records, but not necessarily at one site or in a single environmental setting. Moreover, some areas may not have plant resources that could support increasing populations, and in those cases, intensification would be limited to increasing the exploitation of small terrestrial animals, or aquatic species. Additionally, fluctuations are expected to occur in the directional trends of increasing population densities and land use intensity. For example, some areas may be virtually abandoned due to environmental factors. Or, as Hester (1989) noted, when bison become available in greater numbers, the people would be expected to hunt more bison and do less deer hunting or reduce the level of effort devoted to small game or plant food procurement. Other things being equal, bison hunting probably has a better cost:benefit ratio compared to deer hunting or plant gathering (cf. Thoms, 1989).

1. Late Pleistocene to early Early Holocene: Pre-Clovis through Early Paleoindian (prior to ca. 10,000 B.P.); low population densities, without appreciable population circumscription; high group mobility, short term occupation of sites by family groups; people move to the food resources (Le., "forager-like;" Binford, 1980); reliance on big game to the extent it is present (megafauna, or largest bodied

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ungulates), supplemented by a variety smaller animals, fish, shellfish and plants. Expectations of archaeological record: comparatively few sites with comparatively low artifact densities and high diversity in tool types, especially camp maintenance tools; small, minimal investment features, no evidence for bulk processing foods other than big game.

2. Early Early Holocene: Late Paleoindian (ca. 10,000-8,000 B.P.); increasing population densities and initial population circumscription; somewhat reduced group mobility, but continued forager-like strategies; primary reliance on the largest bodied available ungulates (probably deer in riverine settings, and at least periodically bison in adjacent uplands); increasing use of smaller animals, fish, shellfish and plants, as the availability of larger game animals relative to human population decreases. Expectations of the archaeological record: comparatively more sites, most of which should have low artifact densities and high diversity in tool types, especially camp maintenance tools; small, minimal investment features, no evidence for bulk processing foods other than big game, including deer.

3. Late Early to Middle Holocene: Early Archaic (ca. 8,000-5,000 B.P.); increasing population densities, with population circumscription well established; reduced group mobility; a notable reduction in the use of short term occupation of sites by family groups and the movement of people to the food resources, coupled with an increase in logistically oriented, "collector-like" strategies (Binford, 1980); in the absence of bison, reliance on deer in all settings, and increasingly on smaller animals, fish, shellfish, and especially plants foods (roots, prickly pear, pecans, mesquite, and acorns), focusing on the more abundant species with the best cost:benefit ratios. Expectations of the archaeological record: notable increase in site types, including sites with high artifact densities and diversities (Le., base camps) that can be distinguished from sites with low or high artifact densities and low artifact diversities (Le., task-specific, logistical sites); overall increase in the diversity and frequency of tool and feature types; initial evidence for increased procurement and bulk processing foods other than big game (Le., deer size and larger), including small game, fish, and plant foods.

4. Middle to early Late Holocene: Middle Archaic (ca. 5,000-3000 B.P.); continued increases in population densities and population circumscription; increase in collector-like strategies; continued reliance on deer, but with an increasing focus on riparian zones, and increasing use of smaller animals, fish, shellfish, and especially plants foods; species with the lower cost:benefit ratios than those intensively used in preceding time periods will be used more regularly. Expectations of the archaeological record: notable increase in site types, including sites with high artifact densities and diversities (Le., base camps) that can be distinguished readily from sites with high artifact densities and low artifact diversities (i.e., intensively used task-specific sites); initial appearance of sites with more permanent residential

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structures, and evidence for trade, as well as cemeteries; overall increase in the diversity and frequency of tool and feature types; more evidence for increased procurement and bulk processing resources other than big game, especially plant foods.

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5. Early Late Holocene: Late and Tenninal Archaic (ca. 3,000-1,200 B.P.); continued increases in population densities and population circumscription; increasing collector-like strategies; reliance on deer in all settings, but with an even greater focus on riverine environments and an ever increasing reliance smaller animals, and plant foods with lower cost:benefit ratios than those used intensively during preceding periods. Expectations of the archaeological record: village or quasi­village sites (Le., longer term occupations with more substantial residential structures, middens, and cemeteries) become more common, as do task-specific sites; the pattern of an increase in the diversity and frequency of tool and feature types should continue; bulk processing features (e.g., large earth ovens and burned rock middens) should become more common, as should evidence for the use of fish and shellfish; evidence for trade should become more abundant as well.

6. Late Holocene: Late Prehistoric (ca. 1,200-400 or 5(0); this is essentially the pre­prothistoric land use pattern; it is the period when land use was at its maximum intensity, semisedentism was at a maximum level, and native populations were at their highest level prior to the population apocalypse brought about by the "discovery" of the New World by Europeans and the introduction Old World diseases. Expectations of the archaeological record: the equivalent of the Austin Focus or some other limited or non-bison hunting phase of the well known Late Prehistoric periods; tool and feature assemblages, including storage facilities, should be more complex than in earlier periods, midden deposits at base camp/village sites and special purpose sites should be at their densest, cemeteries should be more common than during any other period, and evidence for violent deaths should be at an all-time high, as should evidence for trade.

Elements of this model are subject to testing and refinement with data from the Richard Beene site and from the Applewhite Reservoir archaeological project in general, as well as from existing and new data generated by other projects in the south and central Texas areas.

TIlE ARCHAEOLOGICAL RECORD AT THE RICHARD BEENE SITE, 4IBX831

The archaeological record at the Richard Beene site is unusually well-stratified, well-preserved, and well-dated. It provides a unique, long-term perspective of the utilization of one locality along the ecotone between the central Texas plateau prairie and the south Texas plains. The site also provides a long-term record of the utilization of a

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riverine landscape. Today, the Medina River is about 90 m north of and 19 m below the Applewhite terrace edge (Figure 3). Judging from the position and slope of a gravel lens exposed near the base of the Perez Paleosol at the near-river end of the dam trench, the Medina River in the immediate vicinity of the site has been confined to the present floodplain since the end of the Pleistocene.

At least 20 stratigraphically discrete archaeological deposits were identified in the upper 12 m of terrace fill, representing all major cultural periods of Holocene age. Paleontological remains were recovered from four Late Pleistocene age, weakly developed "paleosols" buried 12 and 16 m below surface in terrace alluvium (see Mandel and Jacob, this volume for a discussions of the "paleosols" and Baker and Steele, this volume for a discussion of faunal.remains from these sediments).

The archaeological and paleontological remains, as well as the older sediments at the site were dated by some 50 radiocarbon ages, most of which are on soil humates. The set of C-14 ages from soil humates is completely in chronological order (Mandel and Jacob, this volume). All nine dates from wood charcoal, including four obtained using the accelerator mass spectrometry (AMS) technique, are also in correct chronological order. Because most of these C-14 ages were recovered from archaeological features, or from tree burns on occupation surfaces, they probably provide the most reliable age estimates for the archaeological components at the Richard Beene site (Figure 3).

In several cases, there is overlap between the C-14 ages on wood charcoal and on soil humates from the same stratigraphic unit, but in each case, the soil humates contained some wood charcoal as well. The broader pattern, however, is that the C-14 ages derived from soil humates tend to be about 1,000 years older than those on wood charcoal from the same stratigraphic or soil unit. While the estimated C-14 ages derived from wood charcoal are used to date particular occupation zones and surfaces, the C-14 ages derived from soil humates, minus 1,000 years, are used to bracket some of the archaeological periods.

I begin the discussion of the archaeological record at the Richard Beene site by summarizing the excavation strategies we employed during the course of fieldwork. This is followed by descriptions of the general nature and distribution of artifacts and features within each component. The next section discusses some of the intrasite patterns in the archaeological record. A discussion of natural site formation processes follows. I conclude the paper with a few comments about the site's potential to contribute information about long-term land use in the region.

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'OOm

.55m

.5Om

'45m

.4Om

APPLEWHITE TERRACE LATE PREHISTORIC (Arrow points and c.ramlca)

• ~_~_~_~_~~~:;!;~~~~;J;:~:;~~~f=~~~~~=r~:;~~~tj~:-----------~--~~TEARC~Ca~~70~a~ 2 ~ ____ M'DDL£ ARCHA,C I'ppo<) 4.135.70,. B.P ••

_______ MIDDLE ARCHAIC (!owN) .... 570 ~ 70 'P B.P.

tlr-T--__ ~~_r--r-_r--r-r-_.-.. r_-,....-_r--~=;:=.~::::4_}; EAR1.Y ARCHAIC 15.Q30;t.155 'P ap. "'

LEON CREEK PALEOSOl.

5 ___ BASlN-sHAPED FEATURE. 7.1545;t. 70 'If ap,

..... , /

LATE PALEOINDIAN (upPIJ) .... I 15

~I U I J I ._ ________ r-ARE-CRACKED ROCK FEATURE B,080.t 130 'P7 B.P.

/', ,I \ ELM CREEK PAlEOSO:.: ... :::L __ --'----:f--r --\ --7 - - T 1I-r .... ...,r-.,.!::'~,--NDChan::calAg. f.~.p.~=;~:r=T=r:::;;~5i::::=_:..:....__:~-:::=\=::\=~- _LATEPALEOINDIA.N(~)S.15OS;t.75)'1'B.P. •

" ~' a....!.... r '/ rUTE PLEISTOCENE FAUNA 12.745 ;t.l90yr B.P.

- -C - 1 ' I t--1 _______ ~ PEREZ PALEOSOL.

- - - ... - - - - --sOiL:; - - - -,

Sta8fiecl Gravell and Sandi

"SOIL" , L-________ ,' __________________________ ~

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FLOODPLAIN

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e.c. 31702 (ciIIIcolll. _ ..... ""'I Beta 4~El'Ha538 (chllCOoll, heanh) Bata 475271ETH8540 (charcoal. mW.n·.k. cIepoait) ..... _ ..... 1: Excavaled Al.a , 5 8Ita43330(~lII.h'tun) Bat. "7529JE'T"HaS42 (oIwcoaI, hNJ1h) , • 8ata3l700 la-:o •. hI'tun) Be ... 44386 (charcoal, Are-aDad nxk feature)

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B.1I47526/ETH8539 (charcoal, organicbcn.rk:h, amaphoul , .. bJr." (7)

Bata 4 7528fEl'H8S4 1 (charoc.al, burned lurtaoe)

• Approldm.ll. IocaJIon 01 charcoal umpJ.

* ETHI: AMS Tachnlqu.

Figure 3. Schematic cross-section of the dam trench wall at the Richard Beene site (41BX831); view to the west showing the relative positions of the excavated areas and dated deposits.

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Excavation Strategies

The excavation goals for all archaeological deposits at the site were: (1) identify and isolate intact features and well-preserved occupation surfaces representative of each major archaeological component; (2) in the absence of intact features or occupation surfaces, identify and isolate artifact-rich zones; (3) recover as large a spatial (or numeric) sample of artifacts and features as possible; and (4) insofar as possible, recover some kind of sample from each stratigraphically distinctive archaeological deposit exposed by heavy machinery during dam construction.

A backhoe was used to search for and isolate buried features, occupation surfaces, and high density artifact zones for excavation. As necessary, the overlying sediments were mechanically removed to within about 40 cm of the target surface or zone. Next, we hand dug a cross trench in the selected area(s), maintaining 1 m provenience. Excavation was in arbitrary 10 cm levels, unless natural stratigraphy was evident. If the latter was the case, the stratum was subdivided into levels of 10 cm or less. The purpose of the cross trench was to sample from above and below the surfaces or zones selected for excavation, and to obtain extensive profiles of area(s) selected for horizontal excavation. In addition, several 1 X 1 m excavation units were placed within each quadrant delimited by the cross trench to further document the distribution of features or occupation surfaces, as well as to discover additional features.

Both shovel-skim and toweling techniques were employed. All sediments were water-screened through 1/8th inch hardware cloth, and constant volume samples (10 X 10 X 10 cm) for fine screening (water-screening through 1 mm mesh) were taken from each level in each 1 X 1. In the horizontally excavated areas, non-feature sediments were water-screened through 1/4th inch hardware cloth and constant volume samples were take from each 1 X 1 m unit. Features were cross-sectioned to obtain a profile. Feature fill was screened through 1/8th hardware cloth, and constant volume and bulk samples were taken from the fill.

We spent ten months in the field with a field and lab crew ranging in size from about 10 to 40 individuals. More than 600 m2 of artifact bearing sediments were excavated in discrete occupation zones and surfaces. This included about 25 m2 in the Late Prehistoric deposit, 150 m2 in three Late Archaic zones, 55 m2 on two Middle Archaic surfaces, 180 m2 on one Early Archaic surface (Figure 4a), and about 170 m2 in two Late Paleoindian zones (Figure 4b). Smaller areas were excavated in about 10 other places, including the work done in the Late Pleistocene sediments that yielded the paleontological remains. Preliminary counts of recovered cultural materials include, 30,326 pieces of chipped stone debitage, 131 cores, 483 chipped stone tools, 8,530 mussel shell umbos (i.e., hinges), 11,246 bone fragments, and 25,864 pieces of flre-cracked rock, mostly sandstone from local bedrock outcrops.

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Figure 4. a: Photograph of the "gearing up" stage for large-scale excavation of the extensive Early Archaic surface at 41BX831, 6.5 m below the terrace surface; view to the west; b: photograph of the "digging out" after heavy rains during the large-scale excavations of the upper Late Paleoindian zone at 41BX831; view to the southwest.

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The Extent of Hunter-Gatherer Occupations at the Site

When the site was recorded, chipped stone debitage, a few tools, mussel shell fragments, and pieces of fire cracked sandstone were found in a roughly rectangular­shaped area 350 X 50-100 m that extended in an east-west direction along the terrace edge and south onto the terrace surface (Archeological Research Laboratory, 1991: 111). Upon more detailed examination, however, it became apparent that the surface scatter designated as 4IBX831 merged with similar scatters to the east (4IBX830) and west (41BX833). In short, there is a continuous scatter of archaeological material on the terrace edge along this stretch of the Medina River, such that horizontal site boundaries often are set arbitrarily by large, headward-eroding gullies.

17

Backhoe trenches excavated during the testing phase revealed two archaeological deposits buried in silt loam to silty clay loam, a Late Archaic component (ca. 1.25 m below surface) and a Middle Archaic component (ca. 2.6 m below surface) (Archeological Research Laboratory, 1991:111). Subsequent inspections of the cutbanks along the terrace edge and in the headward-eroding gullies showed that the subsurface components merged with the subsurface components of sites to the east and west. We also had the opportunity to observe the pan scrapers as they began cutting the huge trench for the dam's footing, and there too, we found scattered pieces of mussel shell and fire-cracked sandstone.

In the backhoe trench we dug two meters below the surface of the site's previously identified Middle Archaic component, and there we discovered· a fire-cracked rock feature (ca. 4.5 m below the terrace surface). A C-14 age was obtained on the encompassing soil humates: 6,450 ± 135 yr B.P. (Beta 43333; C-13 adjusted). One pattern was becoming clear: this part of the lower Medina River valley was used extensively and perhaps intensively throughout the last several thousand years.

Conformation came when Richard Beene discovered the extensive Early Archaic component 6.5 m below surface in the footprint of the dam. Fire-cracked rock, mussel shell, and chipped stone extended over the entire bottom of the huge trench, an area about 300 X 100 m in size, and into the trench walls. As the pan-scrapers continued to excavate, we observed Late Paleoindian cultural materials in varying densities down to about 12 m below the surface. Several of the deeper features underwent emergency salvage excavations (Figure 3). By then, the picture was clear: the Applewhite terrace preserved evidence of cultural and natural history that has an extraordinary potential to contribute significantly to our understanding of long-term human adaptations, site formation processes, and paleoenvironments.

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Late Prehistoric Component (ca. 1200-400 B.P.)

Excavations confinned the presence of a Late Prehistoric component in the uppermost 30-40 cm of the site (Figure 3), but features were not encountered in the 23 m2

(4.6 m3) we excavated. The apparent absence of features is probably due to the slow rates

of deposition and significant bioturbation during the last millennium or so. Temporally diagnostic artifacts included contracting and expanding stem arrow points (Figure 5z, aa) and several pottery sherds. Preliminary counts on other materials included, 617 pieces of chipped stone debitage, 1 hammerstone, 2 cores, 1 heavy duty tool (i.e., thick edge­modified flake), 126 mussel shell umbos, 40 bone fragments, and 515 pieces of fire­cracked rock. The only identified faunal remains from the Late prehistoric component were frog and large mammal (deer-size) bones.

Compared to other excavated components at the Richard Beene site, occupation during the Late Prehistoric period was less intensive. The kinds of artifacts recovered represent a limited range of activities, including tool manufacturing/refurbishing, hunting, and shellfish procurement. Some of the other sites in the Applewhite Reservoir project area with Late Prehistoric components have features and high artifact densities, as well as diverse tool assemblages.

Late Archaic Component (ca. 1,800 to 3,500 B.P. ?)

We mechanically removed the upper 50 cm of sediments where we planned to excavate the Late Archaic component that had been identified during the testing phase. Hand dug cross-trenches, test pits, and backhoe trench profiles led to the identification of three occupation zones, all of which had fire-cracked rock features, shallow basin-shaped pits, and mussel shell concentrations. In all, we hand excavated a total of 36.1 m3 in the Leon Creek paleosol that developed as the levee formed and houses the site's Late Archaic component (Figure 3).

The relative discreetness of the cultural stratigraphy and the presence of numerous intact features, suggest that deposition was fairly rapid during Late Archaic times. It was not so rapid, however, as to prevent soil development and significant bioturbation that masked occupation "surfaces." As a result, we were only able to identify occupation Ilzones. 11

We excavated about 65 m2 in the upper zone that yielded mainly small, expanding stem Ensor points (Figure 5x). Our excavations focused (ca. 95 m2

) on the middle Late Archaic rone that had the highest density of fire-cracked rock and most of the large, broad blade dart points, including Marcos and Lange types (Figure 5v, w). This rone also encompassed the previously identified, pit feature dated to 3,090 ± 70 (Beta 36702, C-13 adjusted) (Figures 3 and 6a). Further excavation of this rodent-impacted feature showed it

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Figure 5.

.t • ,

D E G H I A

C F

B

e 11 , ,

~ ~ ) '* . M

L N P Q 0 R

J K

+ :

" t: * " ,

AA , . I ' • Z

U X S Y V 0 , , , . w r , "'

Selected artifacts from the Richard Beene site (4IBx831): A-I, artifacts from the upper Late Paleoindian zone; J-R, artifacts from the extensive Early Archaic surface; S, Middle Archaic projectile point fragment from the top of the Medina paleosol; T-Y, artifacts from the Late Archaic zones; Z-AA, artifacts from the Late Prehistoric zone.

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I Figure 6. a: View to the north of the middle Late Archaic zone at 4IBX831; the upper

part of the oven-like feature is shown by the concentration of fire-cracked rocks in the center of the photograph; b: view to the southwest of the upper Middle Archaic surface showing the mussel shell concentration in the center of the photograph.

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to be basin-shaped, about 2.0 m in diameter, and 25 cm deep. Its base was oxidized and further delineated by a thin scatter of fire-cracked rocks. Given its structure, and considering the paucity of chipped stone artifacts and faunal remains in and around the fearure, I suspect it represents a large earth oven that probably was used to cook plant foods.

Only about 20 m2 were excavated in the lower part of the Late Archaic deposit; all of the units were dug in the cross trench. We have not yet completed the initial sorting of artifacts by zone, but the one Langtry-like point (Figure 5u) from the Late Archaic component was recovered from the deepest part of the deposit.

The types of comer-notched and stemmed dart points from the Late Archaic components are consistent with the date on the oven-like feature and with other dates from the Leon Creek paleosol ranging from 2,800 to 3,500 B.P. (see Mandel and Jacob, this volume), considering that ages on soil humates tend to be about 1,000 years older than those on wood charcoal. This, in combination with the presence of the lower zone about 50 cm below the 3,000 year old earth oven-like feature, suggests that the Late Arachic (/late Middle Archaic 7) zones at this site date between about 3,500 and 1,800 B.P. Most of the fearures were charcoal-poor, but several contained small pieces of wood charcoal. We plan to submit a few of the samples for C-14 dating by the AMS technique to obtain more reliable age estimates for the various Late Archaic zones.

Preliminary counts on recovered materials included, 8,571 pieces of chipped stone debitage, 4 hammers tones, 23 cores (e.g., Figure 5t), 23 heavy duty tools (i.e., thick edge­modified flakes and cobble tools), 24 light duty tools (i.e., less than 1 cm thick, Le., thin edge-modified flakes), 7 thick bifaces (more than 1 cm thick), 33 thin bifaces (1 cm or less thick), 10 projectile points, 3 nonflaked (Le., ground, pecked, or incised) tools, 2,685 mussel shell umbos, 1,798 bone fragments, and 13,396 pieces of fire-cracked rock.

Dart points and preforms or unnotched bifaces were the only formal artifact types in the assemblage (Figure 5u-y). Preservation of recovered bone was comparatively good. Deer, beaver, canid, rabbit, several kinds of small rodents, frog, turtle, and snake remains were identified in the various Late Archaic zones (Baker and Steele, this volume).

Middle Archaic Component (ca. 4,100 and 4,600 B.P.)

We used a backhoe to remove about 2 m of alluvium overlying the previously identified Middle Archaic component, and in the process we discovered an archaeological deposit about 40 cm above the lens of artifacts identified during the testing phase (Figure 3). It was a discrete occupation surface marked by a 3 m diameter, thin lens of mussel shells in sandy silt deposits that formed the base of the levee (Figures 6b). Almost all of the shells were in horizontal angles of repose, suggesting that the feature was well

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preserved. This occupation also had several welI-preserved, basin-shaped, rockless hearths about 40 cm in diameter and 15 cm deep. Wood charcoal from a tree burn on/near the occupation surface yielded a C-14 age of 4,135 + 70 yr B.P. (Beta 43330, C-13 adjusted).

The lower Middle Archaic surface (ca. 2.6 m below surface) is in the upper part of the Medina Paleosol (Figure 3; see Mandel and Jacob, this volume, for a discussion of this paleosol). The C-14 age on wood charcoal from a tree burn at the surface of the paleosol was 4,570 ± 70 yr B.P. (Beta 38700, C-13 adjusted). A dense scatter of lithic debris, with almost all of the flakes in horizontal angles of repose, and small, basin­shaped, rockless and rock-filled features demarcated this well-preserved surface.

Preliminary counts on recovered materials from both surfaces included, 1,999 pieces of chipped stone debitage, 1 thin biface, 1 projectile point fragment, 253 mussel shell umbos, 229 bone fragments, and 295 pieces of fire-cracked rock.

Most of the faunal remains were from deer and rabbit-sized animals. The closest item to a time-diagnostic tool was a small biface fragment that appears to be a barb from a dart-size projectile point Nearby, however, we collected a fragment of a deeply comer­notched, BelVAndice type dart point (Figure 5s) from a setting stratigraphically identical to the lower Middle Archaic surface (ca. 4,600 B.P.) at the top of the Medina Paleosol. We also colIected several large wood charcoal samples from in situ tree burns in the top of the Medina paleosol where it was exposed in the dam trench. Some of these will be submitted for C-14 dating.

Early Archaic (ca. 5,500 to 8,000 B.P.)

Prior to abandoning work on the Middle Archaic surfaces, we dug a series of backhoe trench to search for older archaeological deposits. It was in one of these trenches that we discovered the fire-cracked rock, hearth-like feature (ca. 4.5 m below surface) that yielded the C-14 age on soil humates of 6,450 ± 135 yr B.P. (Beta 43333; C-13 adjusted). We excavated the feature and a small area around it and recovered a few flakes and pieces of mussel shell. The feature was encased in the Median paleosol about 2.0 m below its truncated surface.

To the extent that C-14 ages on soil humates in the site area are 1,000 years older than ages on wood charcoal, this feature is expected to have a C-14 age of about 5,500 RP., or perhaps somewhat older, considering that the small amount of wood charcoal in the bulk sediment sample probably affected the 6,450 B.P. age estimate. In any case, the feature and associated artifacts represent the youngest of the Early Archaic materials at the Richard Beene site.

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Before discussing the extensively excavated Early Archaic surface, (ca. 7,000 B.P.), two other feature areas merit mention because they provide useful information about the intermittent use of the site during the Early Archaic period. The ftrst of these is a basin-shaped (ca. 0.9 X 0.4) hearth-like feature ftlled with carbon-stained sediments and a few pieces of mussel shell and fire-cracked sandstone. It was exposed in the wall of dam trench in the B horizon of the Elm Creek paleosol that underlies the Medina paleosol (Figure 3). A small piece of wood charcoal from the feature yielded an AMS C-14 age of 7,645 ± 70 yr B.P. (Beta 47529/ETH-8542, C-13 adjusted).

The second feature, a discrete concenO'ation (ca. I m diameter) of fire-cracked sandstone, was discovered in what appeared to be the upper part of the C horizon of the

. Elm Creek paleosol (see Mandel and Jacob, this volume, for a description). It was sn-atigraphically associated with a sparse scatter of chipped stone debitage, mussel shell, and pieces of ftre-cracked rock. However, because its discovery and subsequent salvage excavation was literally in the pathway of the pan scrapers working in the darn O'ench, the precise sO'atigraphic position within the Elm Creek paleosol is not entirely clear (Figure 3). In any event, the feature contained a few small pieces of wood charcoal that yielded a C-14 age of 8,080 ± 130 yr B.P. (Beta 38700. C-13 adjusted). A second C-14 age was obtained from bulk carbon (including even smaller pieces of wood charcoal): 8,010 ± 70 yr B.P. (Beta 44386, C-13 adjusted). This feature and the associated cultural materials are considered to be the oldest of the Early Archaic remains at the site.

When Richard Beene, the site's namesake, reported his discovery of the extensive Early Archaic component buried 6.5 m below the surface nearby in the dam ttench, we quickly geared up for large-scale excavations in the footprint of the dam (Figures 3 and 2b). Our water screening system was upgraded, the crew size tripled, and we excavated more than 180 m 2 of an unusually well-preserved, Early Archaic living surface in the silty clay loam sediments at the base of the Medina paleosol (Figure 4a).

As we geared up for work, we submitted bulk sediment samples from four charcoal-stained, ftre-cracked rock features for C-14 dating. The age estimates ranged from about 6,400 to 7,900 B.P., and averaged 7,200 B.P. Subsequently, we submitted four very small wood charcoal samples from three other hearth features and a tree burn on the same surface for C-14 dating by the AMS technique.

The elevation of the three features and the ttee burn varied only by about 30 cm over an area 100 X 10 m in size. C-13 adjusted age estimates were as follows: (1) 6,985 ± 65 yr B.P. (Beta 47523/ETH-8536) from the O'ee burn; (2) 6,900 ± 70 yr B.P. (Beta

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47524/ETH-8537) from a hearth; (3) 6,930 + 65 yr B.P.(Beta 47525/ETH-8538) from a ·1 hearth; and 7,000 ± 70 yr B.P. (Beta 47530/ETH-8543). The "pooled average" is 6,954 ± 34 yr B.P., calibrated to 5,805 B.C. (5,951-5,740 B.C.).

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Almost all the mussel shells, lithic tools, and other artifacts were found in horizontal angles of repose, indicating that this component had not been adversely impacted by high energy floods or subjected to significant bioturbation. Moreover, rodent burrows, root casts, and other forms of bioturbation were limited. All of the cultural material appeared to within a single depositional unit. We estimated that, in any give place within the area we excavated, about 90 percent of the cultural material was confined to lens no more than 10 cm thick.

The pan scrapers, especially those with teeth, damaged the site to some extent, but most of the approximately 35 recorded features were in good condition. Two types of hearth features were especially common at the site: (1) those with a fire-cracked rock lens in shallow (ca. 10-15 cm deep), circular to oval, basin-shaped pits (ca. 40-60 cm) with oxidized bottoms and sides (Figure 7a); and (2) those in a rockiess, basin-shaped pit of similar size with oxidized bottoms and sides, and typically ftIled with carbon-stained sediments (Figure 7b). Other feature types included, mussel shell concentrations up to several meters in diameter, fire-cracked rock concentrations about 1 m in diameter (hearths or ovens ?), oxidized areas, and sparse "sheet middens" with bone, mussel shell, chipped stone debitage and tools, fue-cracked sandstone, and carbon-stained sediments.

Preliminary counts on recovered materials from this surface included, 10,638 pieces of chipped stone debitage, 1 harnmerstones, 19 cores (Figure 5j), 14 heavy duty tools (i.e., thick edge-modified flakes and cobble tools), 32 light duty tools (i.e., thin edge-modified flakes), 11 thick bifaces (more than 1 cm thick; Figure 50), 15 thin bifaces (1 cm or less thick), 12 projectile points, 1 nonflaked (i.e., ground, pecked, or incised) tool, 2,038 mussel shell umbos, 4,850 bone fragments, and only 875 pieces of fire-cracked rock.

Projectile points dominated the formal tool assemblage. All but one were stemmed/indented-base types, similar to Bandy, Gower, Martindale, and Uvalde points (Figure 5p-r). The exception was a lancelot point morphologically similar to the Angostura type, but technologically similar to the stemmed/indented base types. To me, this suggests that the lance lot-shaped point may be a refurbished stemmed/indented-base form, possibly reworked after a barb(s) or shoulder(s) was broken. Most of stemmedlindented-base forms are complete or nearly complete, but many have been reworked. Other tools included preforms/thin bifaces, a single drill fragment, and burin blades and cores (Figure 5k-n).

Faunal remains were more numerous, varied, and better preserved than in the other components. The recovered skeletal elements included those from deer, pronghorn, canid, porcupine, rabbit/hare, rat, gopher, squirrel, other small rodents, fish, turtles, and snakes. By volume, deer-size animals dominate the Early Archaic faunal assemblage, although the effects of taphonomic factors remain to be determined (see Baker and Steele, this volume).

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Figure 7. a: Photograph of an intact, basin-shaped hearth feature with a fire-cracked rock lens, Early Archaic surface, 4lBX831; b: photograph of an intact, basin­shaped, rockless hearth feature, Early Archaic, 4lBX831.

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Some of the features overlap horizontally, and in a few cases, "sheet middens" cap hearth features. This suggests there were multiple occupations of the same surface. Several lines of evidence, however, convince me that the surface was available for occupation for only a brief span of time, perhaps no more than a generation or so, before it was buried by alluvium: (I) the AMS C-14 ages on features from across the site are virtually identical; (2) the effects of bioturbation are minimal, as evidenced by the presence of so many remarkably well preserved features, and the fact that almost all of the cultural materials are confined to 10 cm thick lens; and (3) the sediments encasing the cultural remains are at the bottom of the Medina paleosol, where deposition should have been comparatively rapid (see discussion below).

Late Paleoindian (ca. 8,700 to 9,700 B.P)

As we completed our excavation of the extensive Early Archaic surface, we dug a series of backhoe trenches 2.5 m below that surface to discover older archaeological deposits. In the bottom of one of those trenches (ca. 9 m below the modern terrace surface), we found a lens of fire-cracked sandstone, mussel shells, and chipped stone, mixed with small stream worn cobbles (ca. 2-4 cm. diameter) in a fine sandy silt matrix. Subsequent trenching and observations made walking behind the pan scrapers revealed that the artifact-rich zone extended over an area larger than 100 X 100 m at the base of the Elm Creek paleosol and in the upper part of the Perez paleosol (Figure 3; see Mandel and Jacob, this volume, for a discussion of these paleosols).

Bulk sediment samples encasing the archaeological remains at the bottom of the Elm Creek paleosol were submitted for rapid turn-around C-14 age determinations. The results came back as 9,780 + 120 yr B.P. (Beta 43877, C-13 adjusted) and 9,750 ± 130 yr B.P. (Beta 43878, C-13 adjusted). We also have a series of C-14 ages, in correct chronological order, on soil humates from the upper part of Perez paleosol. The ages range from 9,660 ± 100 yr B.P. (Beta 47564, C-13 adjusted) for the truncated surface, to 10,780 ± 140 yr B.P. (Beta 44543, C-13 adjusted) on B horizon sediments about 1.3 m below the truncated surface (see Mandel and Jacob, this volume).

Almost all of the cultural materials believed to be Late Paleoindian in age were recovered from sediments bracketed by these age estimates. The lowermost defmite cultural deposit we excavated ("salvaged") at the site, a fire-cracked rock feature (ca. 1 m in diameter), was at the bottom of the Perez paleosol, immediately overlying the Somerset paleosol, but it is not necessarily any older than the other Late Paleoindian cultural materials (Figure 3). Carbon-sediments and a few very small pieces of charcoal were recovered from immediately beneath the lens of fire-cracked rock and will be submitted for dating by the AMS technique.

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So far, we have only one C-14 age on wood charcoal from a cultural feature in the upper part of the Perez paleosol. The very small charcoal sample came from a sparse, midden-like deposit of fIre-cracked rock, mussel shells, chipped stone, bone fragments, and charcoal flecks in the lower Late Paleoindian zone about 40-50 cm below the truncated surface of the Perez paleosol. It yielded an AMS C-14 age of 8,805 ± 75 yr B.P. (Beta 47527/ETIl-8540, C-13 adjusted). I believe that this age estimate is the most reliable one for Late Paleoindian occupation zones where we did most of our work.

The charcoal for the AMS age estimate came from precisely the same part of the B horizon and within 4 m of the bulk sediment sample that yielded an age of 9,870 ± 120 yr B.P. (Beta 47565, C-13 adjusted). By applying the 1,000 year discrepancy to the C-14 ages on soil humates that bracket almost all of the cultural remains, we come up with an estimated age for the site's Late Paleoindian component of approximately 8,700 to 9,700 B.P., a range compatible with the 8,800 B.P. age estimate from wood charcoal.

About 150 or were excavated in what we called the upper Late Paleoindian zone, or the materials recovered from the lowermost part of the Elm Creek paleosol and on the eroded surface of the Perez paleosol (Figure 3). Most of the artifacts were distributed through 10 to 30 cm of stratifIed sandy silt alluvium overlying the eroded Perez Paleosol. Unfortunately, this zone was not nearly as well-preserved as the younger parts of the site. In fact, we did not fInd any in situ features.

What we found were essentially random concentrations of chipped stone artifacts, fIre-cracked rocks, mussel shells, and stream worn pebbles up to about 4 cm in diameter (Figure 8a). Many of the artifacts rested on their edges (vertical angles of repose), sometimes imbricated, in small erosional gullies or rills, and in potholes eroded into the silty clay sediments of the Perez paleosol. The obvious implication here is that the artifacts, as well as the small cobbles, form a lag deposit that resulted from a comparatively high energy flood that eroded the top of the Perez paleosol.

It is important to point out, however, that the cultural materials included pieces of fIre-cracked rock and chipped stone artifacts that were up to 15 cm in maximum dimension, and thus several times larger than any of the stream worn cobbles. Moreover, the edges of the fIre-cracked rock did not seem to be signifIcantly rounded, and even the small flakes were razor sharp. This suggests that the cultural material was not transported very far as part of the bed load of the flood(s).

Preliminary counts on recovered materials from the upper Paleoindian zone included, 6,858 pieces of chipped stone debitage, 2 hammerstones, 82 cores (Figure 5t), 111 heavy duty tools (i.e., thick edge-modifIed flakes and cobble tools), 114 light duty tools (Le., thin edge-modified flakes), 15 thick bifaces (more than 1 cm thick; Figure 60), 10 thin bifaces (1 cm or less thick), 12 projectile points, 1 nonflaked (Le., ground, pecked,

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Figure 8. a: Photograph of a lag-concentration of fIre-cracked rocks, mussel shells, chipped stone, and smaIl, stream worn cobbles in the upper Late Paleoindian zone, 4IBX831; b: photograph of an intact, hearth-like feature defIned by a ring of fife-cracked rock in the lower Late Paleoindian zone, 4IBX831.

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or incised) tool, 2,731 mussel shell umbos, only 347 bone fragments, and 9,366 pieces of fIre-cracked rock.

All but one of the relatively complete projectile points were Angostura types represented by proximal ends (Figure 5h-i). Interestingly, the only complete point was a stemmed, indented-base specimen similar to the ones from the Early Archaic component (Figure 5g). Two of the lancelot points were reworked to form drills. Gouge-like tools-­bifacial Clear Fork tools (Figure 5f)--were as common as points, and gravers (Figure 5e) were almost as common .. Other artifacts in this diverse assemblage, included cobble cores (Figure 5a), blade-like flakes (Figure 5c), and burin blades (Figure 5b), and burin cores (Figure 5d). Artifact types present in this assemblage, but either absent or virtually absent in the younger assemblages, include the gouge-like tools, the large burin blades and blade-like flakes, the beaked, graver-like tools, and several well-made scrapers. Although we have not yet controlled for sample size, the diversity of tool types suggests that a wider range of tasks were carried out here than other places and during other times at the site.

Faunal remains other than mussel shells were scant The few recovered bone fragments were small and rounded. Here too, deer and rabbit-sized animals were comparatively well-represented.

We also sampled (ca. 20 m2) a lens of artifacts exposed in the wall of the dam

trench about 1.0-0.45 m below the eroded surface of the Perez paleosol (Figure 3). Compared to the upper Late Paleoindian zone on the eroded surface, most of the artifacts from the lower zone were in horizontal angles of repose, and stream-worn pebbles were smaller and fewer in number. We excavated a well-preserved, hearth-like feature that consisted of a ring of fire-cracked rocks lining the edge of a small pit (Figure 8b). Compared to the overlying zone, faunal remains, including deer and rabbit-size mammals, were more numemus, larger in size, and not as well-rounded.

Preliminary counts on recovered materials from the lower Late Paleoindian zone included, 720 pieces of chipped stone debitage, 1 hammers tone, 1 core, 3 heavy duty tools, 1 light duty tool, 1 thick biface (a Clear Fork-like tool), 1 thin biface (a well made drill, possibly from a reworked lancelot point), 2 projectile points (Angostura and Plainview-like), 123 mussel shell umbos, 189 bone fragments, and 452 pieces of ftre­cracked rock, including 124 from a caliche-like material. A few pieces of this material were recovered from the upper zone as well. The caliche-like material is identical to the BK horizon of the Somerset paleosol (Figure 3), suggesting that the eroded Somerset surface was exposed somewhere in the vicinity during the Late Paleoindian period.

With the discovery of a Plainview-like point base, we thought this might be a pre­Angostura component However, the lower assemblage compared well to the overlying one, in that it too contained the base of an Angostura point, a Clear Fork-like tool, and a

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well-made drill. This suggested functional, if not temporal similarities, between the two zones. Temporal similarities are suggested more directly by overlapping C-14 ages on

26

soil humates from the upper and lower Late Paleoindian zones. The AMS C-14 age of 8,805 + 75 yr B.P. on wood charcoal was from the sparse midden-like deposit in the lower Late Paleoindian zone. Compared to the upper zone, the importance of the lower one is that it has significantly better preservation of faunal remains, intact features, and it does not seem to have been subjected to the kinds of erosion that occurred when the Perez paleosol was truncated.

Late Pleistocene Deposits

The last part of the field work at the Richard Beene site was in what we came to call the "turtle trench" that exposed a series of weakly developed "paleosols" ("soils" 6, 7, and 8) between 12 and 16 m below the terrace surface (Figures 3, 9a, and 9b). The trench was so named because of the density and variety of turtle remains that it contained (Baker and Steele, this volume). All of the sediments we sampled in this trench were below the Perez paleosol. Faunal remains were recovered from a lens of well sorted sandy sediments between two thin gravel lenses and from each of the three weakly developed paleosols.

"Soil" 7 produced some burned bone and a possible marine shell fragment, although no defmite cultural materials were recovered. Several very small pieces of charcoal from an amorphous, organic-rich, and fauna-rich area in that strata yielded an AMS radiocarbon age of 12,745 + 190 yr B.P. (Beta-47526IETH-8539, C-13 adjusted). The C-14 age on soil humates from the same area was 13,640 + 210 (Beta 47559, C-13 adjusted), again showing the 1,000 year discrepancy between ages on wood charcoal and soil humates. C-14 age estimates from the turtle trench ranged from about 13,500 RP. for the "B horizon" of "Soil" 6 to about 15,300 for the "C horizon" of "Soil" 8 (see Mandel and Jacob, this volume).

Because the Applewhite Reservoir construction project was terminated unexpectedly, we were only able to examine a few meters of backhoe trench profiles and to carefully excavate a few m1 within the approximately five vertical meters of alluvium between the 8,800 yr B.P. Late Paleoindian deposit buried near the top of the Perez paleosol and the fauna-rich sediments that yielded the 12,745 yr B.P. radiocarbon age. Considering that Plainview, Folsom. and Clovis materials have been excavated from sites within a few tens of kilometers of this part of the lower Medina River valley, the Richard Beene site may yet yield materials from the Early Paleoindian period. It is also evident that there are well-preserved habitable surfaces that date to pre-Clovis times.

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Figure 9. a: View of the "turtle trench" in Late Pleistocene deposits, 12-16 m below the terrace surface at 41BX831; b: photograph of the "turtle trench" wall showing the weakly developed "paleosols:" "Soils" 6 (uppermost), 7 and 8 (lowermost).

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Comments on Natural Site Fonnation Processes at the Site

This section of the paper focuses on site fonnation processes and resulting preservation conditions in two different floodplain settings: the comparatively high-energy environment of the Late Pleistocene, and the lower-energy system characteristic of the Early Holocene. For most of the last 15,000 years, the lower Medina River has been a low-gradient, flood-prone system, with floodplain alluvium consisting mainly of fine sandy and silty clay loams. The approximately 50 C-14 ages from the site lend credence to Mandel's (1991) suggestion that the ostensibly well-developed paleosols fonned in rapidly-deposited, preconditioned sediments.

Most of the paleosols are silty clay loams, but there is considerable variation in the quantity of stream worn gravels. The amount of gravel in the sediments affords a relative measure of energy levels. Gravel-rich sediments were limited to the Late Paleoindian components on and in the Perez Paleosol, and the lower component has significantly less gravel than the upper one (Figure 10). As noted earlier, the presence of an intact fire­cracked rock feature in the lower Late Paleoindian component indicated that it was better­preserved than the upper component, where many of the artifacts were in potholes and rills on the eroded surface of the paleosol. During the early HolocenelLate Pleistocene, local uplands, as well as the Edwards Plateau, were source areas for stream-worn gravels.

Preliminary analyses suggest that the fine-grained sediments comprising the terrace fill derived from soils developed in the Glenrose Limestone on the Edwards Plateau (Mandel 1991; Mandel and Jacob, this volume). These "soil sediments" seem especially prone to forming high viscosity flows. High viscosity flows tend to result in rapid rates of deposition, and they can also entrap and transport gravels. If velocity was sufficiently high, these flows might altogether remove the lighter fraction of archaeological clasts, such as bones, charcoal, and smaller flakes. The heaviest fraction, including larger fire­cracked rocks and pieces of chipped stone, might be transported for very short distances.

This kind of scenario could account for the lag-like character of the upper Late Paleoindian component. A somewhat lower velocity flow might remove the lighter fraction, but leave the heavier fraction, and result in a situation similar to the better­preserved, lower Late Paleoindian component.

The volume of gravel recovered from the archaeological screens shows that the well-preserved Early Archaic component is gravel-poor, as is true for all the younger components (Figure 10). The paucity of gravels is consistent with the idea that lower­velocity, high viscosity flows covered the occupation surfaces without significantly affecting the archaeological deposits. A probable result would be a well-preserved archaeological deposit, much like our Early Archaic component. Here, almost all the artifacts were in horizontal angles of repose, pit feature boundaries were abrupt, fire­cracked rocks were typically in situ, and the faunal material was better preserved than it

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Stream Worn Pebbles 1200

I .. ··· .... · .. ·· .. · ........ · ...... · .. ·.... .... ........ ............ .......................................................................... ...... ............ ..... ........... ....... ............ ..... ...... ..... .................... ..... ..................................................... ..................... ..... ......... 1

1000 I································· ................................................................................................................................................................................. .

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Figure 10.

Late Prehistoric Middle Archaic Upper/Late Paleo. Late Archaic Early Archaic Lower/Late Paleo.

Graph showing the weight/density of stream worn cobbles (recovered from archaeological screens) by component at 41BX831.

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was in any other component at the site, although many taphonomic issues remain to be addressed.

28

To me, these archaeological data, independent of any C-14 age estimates, demonstrate that the Early Archaic surface is not likely to have been exposed to the elements for even centuries, let alone a millennium and a half. These data also suggest that agents of bioturbation did not have enough time to significantly disturb the features. From an archaeological perspective, it seems likely that the surface was exposed for a few decades at most, and that the preconditioned nature of the sediments, a la Mandel (1991), accounts for the well-developed character of the paleosol that encompasses the archaeological deposit. .

Patterns in the Site's Archaeological Record

One of the more striking patterns is evident in the nature of raw materials for chipped stone tools and in the basic approaches to tool manufacturing that appear to have changed little during the 9,000 years of intermittent occupation. The initial results of the lithic analysis show that almost all of the cores are from stream worn chert cobbles readily obtained from gravel bars in the river or from gravel lenses exposed in cutbanks near the water's edge. As noted previously, the river probably has been confIned to the present day floodplain area for 10,000 or more years. This suggests that the site's occupants always had ready access to fIst-size, good quality, stream worn, chert cobbles that originated somewhere upstream on the Edwards Plateau.

An inter-component comparison of the densities of harnmerstones, cores (almost all are multidirectional cobble cores), debitage, and thick bifaces (many may have functioned as cores before being used as tools) shows considerable similarities among the Late Archaic, Early Archaic, and Late Paleoindian assemblages, all of which have similarly large sample sizes (Figure 11). To the extent that this suite of artifacts can be considered as a proxie for the tool manufacturing assemblage, it is also evident that the Late Prehistoric assemblage compares favorably. The absence of thick bifaces may be related to the comparatively small size of its spatial and numeric sample. The anomalous nature of the Middle Archaic assemblage may also a result of its small sample size. In any event, the density of debitage is similar to other components, and raw materials are virtually identical as well.

Other patterns evident from the results of our preliminary analyses include the following:

1. Projectile points are the only tool type common to all components, and they occur in similar densities (Figure 12). Thin bifaces (also indicative of hunting-related activities) are present in all but the Late Prehistoric assemblages, the one with the

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---

Late Prehistoric Component Late Archaic Component Middle Archaic Component

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Log-scale graph of the densities of hammerstones, cores, debitage, and thick bifaces (possibly cores) from the various components at 41BX831.

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Late Prehistoric Component Late Archaic Component Middle Archaic Component

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Figure 12. Graph of the densities of classes of stone tools and artifacts from the various components at 41BX831.

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2.

3.

29

smallest sample, but their inter-assemblage densities vary considerably. It is also apparent that the Late Archaic assemblage has a comparatively high density of thin bifaces. These preliminary data suggest that hunting large game (deer-size and larger), or preparing to do so, was an important activity throughout the occupational history of the site.

Although the total faunal sample size is small compared to some sites in the region and issues concerning intra-component taphonomoy remain to be resolved (Baker and Steele, this volume), deer and deer-size faunal remains were the only taxa/class common to all components. This too is consistent with the proposition that hunting large game animals was always an important activity at the site. McGraw has discussed the importance of deer as a food source through the millennia in the northern part of Bexar County (1985b).

Expediency tools on thin flakes (less than 1 cm thick, and presumably used for comparatively light duty tasks), as well as those made on thick flakes (for comparatively heavy duty tasks), tend to be the most common tool types (Figure 12). The exceptions are the component assemblages with small sample sizes (Late Prehistoric and Middle Archaic), but as the lithic analysis continues, we are finding more edge modified flakes in the "debitage" category. There is considerable inter­and intra-component variation in the densities heavy duty versus light duty tools that remains to be explained.

4. The comparatively high density of cores as well as heavy and light duty tools in the Late Paleoindian is also readily apparent (Figure 12). Some of the increase in density might be explained if the lagged artifacts represent several occupation surfaces. It is also possible that the overall distinctiveness of the Late Paleoindian assemblage, including the presence of gouge-like and graver-like tools, in higher frequencies than the other components may be explained mainly by the significantly larger sample size. Alternatively, these tools may provide an indication that woodworking, or some other activity, was comparatively more important.

5. Fire-cracked sandstone and mussel shells are elements common to all components (Figure 13). The sandstone probably was procured from nearby outcrops of sandstone bedrock and the river was probably the source for all of mussel shells. In this setting, fire-cracked rock and mussel shells can be assumed to represent food processing activities. Inter-component variation in their densities, however, suggests variation in intensity of use of the particular places on the landscape. It is interesting to note that there is a better correlation between the density of mussel shell umbos (Figure 13) and chipped stone tools (Figure 12), than there is between fire-cracked rock and chipped stone. This suggests that the density of mussel shell umbos (a measure of one kind of food procurement) may be a more reliable

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Graph showing the weight/density of fire-cracked rock and mussel shell umbos by component at 4IBX831.

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6.

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measure of occupation intensity than fire-cracked rock (a measure of various kinds of food processing). Stated differently, fIre-cracked rock may not be integral to all forms of food processing.

Small (ca. 30-50 cm diameter), basin-shaped features with varying amounts of fIre­cracked sandstone that probably represent hearths or earth ovens are common to all components, except the Late Prehistoric which lacks intact features altogether. Similar size, rockless, basin-shaped features with oxidized bottoms, as well as mussel shell lenses are common to all the Archaic components. These data suggest some similarities in food preparation and utilization through the millennia.

CONCLUDING COMMENTS

One of the more important conclusions that stems from archaeological and paleoenvironmental investigations carried out as part of the Applewhite Reservoir archaeological project is that the Applewhite terrace has preserved important evidence about cultural and natural history. This evidence has an extraordinary potential to contribute signifIcantly to our understanding of long-term human adaptations, site formation processes, and paleoenvironments in general, not just for the lower Medina River valley and adjacent regions.

These preliminary results also demonstrate something that many archaeologists, geoarchaeologists, and geomorphologists have long maintained: the river valleys in the upper part of the Gulf Coastal Plain of Texas, from the Sabine River to the Rio Grande, are likely to contain deeply buried and well-preserved archaeological, paleontological, and paleoenvironmental records of the Late Pleistocene and Holocene times. What we need to do is to learn how to effectively and efficiently learn more about the nature and distribution of these records.

It is worth repeating that the archaeological record at the Richard Beene site is unusually well-stratifIed, well-preserved, and well-dated. And it provides a uniquely long­term perspective of the utilization of a riverine locality along the ecotone between the central Texas plateau prairie and the south Texas plains, as well as of generalized riverine landscapes in subtropical, subhumid environments. The site can serve as a kind of "type record" against which less well-preserved or less complete archaeological records can be compared. Its well-stratifIed and well-dated components offer an opportunity to fIne-tune some of our ideas about temporally diagnostic artifacts.

Results of on-going paleoenvironmental studies promise to tell us much more about the dynamics of landscape evolution, and site formation processes, as well as about the availability of food resources. Data resulting from floral, faunal, lithic analyses should yield important information about how the Indian people used the local landscape through

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the last 10,000 years or longer. We are fortunate indeed to be able to study such a complete record of the local cultural and natural history. The opportunity to do this is a testament to the cooperation among the City Water Board, federal and state regulatory agencies, and the engineering and construction fInns involved in the Applewhite Reservoir Project.

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ACKNOWLEDGEMENTS

Investigations at the Richard Beene site and for other parts of the Applewhite Reservoir archaeological project (ARAP) are funded by the San Antonio City Water Board. The studies are carried out under the auspices of the Archaeological Research Laboratory (ARL), Departtnent of Anthropology, Texas A&M University through Freeze & Nichols, Inc., the engineering finn responsible for the design and management of the Applewhite Reservoir construction project. The U.S. Anny Corps of Engineer, Fort Worth District oversees the project (including its archaeological component) for the federal government, and the Texas Historical Commission is responsible for cultural resource management concerns at the state level.

David Carlson(Co-PI for ARAP, and ARL's head), Patricia Clabaugh (ARL's Lab Supervisor), and Gentry Steele read and commented on earlier versions of the text. Their comments, as well as further discussions with them and Role Mandel, led to substantial improvements in the manuscript. Ben Olive (ARL's data manager), spent many hours generating the numeric data used in the paper and preparing the graphs, including the schematic cross-section diagram of the Richard Beene site. John Dockall (ARAP's lithic analyst) did the artifact illustrations, and Henry Lares drew the physiographic map. While the assistance provide by these and other individuals who had much to do with "getting things right" is greatly appreciated, I bear the responsibility for the paper's content, including any errors of fact or omission.

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Point Survey. Bulletin of the Texas Archeological Society, 57:27-68.

Neck, Raymond W. 1991 The Diary of Jean Louis Beriandier: An Environmental View of South Texas and

Adjacent Mexico, 1828-1834. In: A. Joachim McGraw, John W. Clark, Jr., and Elizabeth A, Robbins (eds.), A Texas Legacy, The Old San Antonio Road and the Caminos Reales: A Tricentennial History, 1691-1991. pp. 269-281. Texas State Department of Highways and Public Transportation, Austin,

Odum, E.P, 1971 Fundamentals of Ecology. W. B. Saunders, Philadelphia.

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Robbins, Elizabeth A. 1991a The First Routes into Texas: A Review of Early Diaries. In: A. Joachim

McGraw, John W. Clark, Jr., and Elizabeth A. Robbins (eds.), A Texas Legacy. The Old San Antonio Road and the Caminos Reales: A Tricentennial History, 1691-1991, pp. 61-113. Texas State Department of Highways and Public Transportation, Austin.

Robbins, Elizabeth A. 1991b The Natural Setting Encountered: The Scenic Landscape. In: A. Joachim

McGraw, John W. Clark, Jr., and Elizabeth A. Robbins (eds.), A Texas Legacy, The Old San Antonio Road and the Caminos Reales: A Tricentennial History. 1691-1991, pp. 245-268. Texas State Department of Highways and Public Transportation, Austin.

Thoms, Alston V.

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1989 The Roots of Northern Hunter-Gatherer Intensification: Camas and the Pacific Northwest. Unpublished Ph.D. dissertation, Washington State University, Pullman.

Thoms, Alston V., John L. Montgomery, and Alice W. Portnoy 1981 An Archaeological Survey of a Portion of the Choke Canyon Reservoir Area in

McMullen and Live Oak Counties. Texas. Center for Archaeological Research, Choke Canyon Series: Volume 3, Center for Archaeological Research, University of Texas at San Antonio.

Turner, Ellen Sue, and Thomas R. Hester 1985 A Field Guide to Stone Artifacts of Texas Indians. Texas Monthly Press, Austin.

Weir, Frank A. 1985 An Early Holocene Burial at the Wilson-Leonard Site in Central Texas. Mammoth

Trumpe!, 2(1): 1 ,3.

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THE BALCONES ESCARJ>MENT-­BORDERLAND OF TIlE AMERICAN WEST

C.M. Woodruff, Jr. Consulting Geologist

GENERAL OVERVIEW The Balcones Escarpment marks a major break in the land. It is a line of hills that extends

through Central Texas and separates the coastal prairies and intervening low, wooded hills from the limestone uplands to the west. The escarpment extends along an arcuate trend from Del Rio on the Mexican border, north through San Antonio, Austin, and Waco. It is the dividing line between two of the grand physiographic divisions of North America: the Great Plains extend west of the escarpment; the Coastal Plains lie to the east (Fenneman, 1931). In Central Texas, this boundary is seen in the change from Hill Country/Edwards Plateau on the west to Blackland Prairie on the east Relief within typical topographic quadrangles range from 50 ft to 300 ft along the inner Gulf Coastal Plain. West of the escarpment, relief generally ranges from 400 ft to as much as 1,200 ft within a typical quadrangle.

The Balcones Escarpment delineates the southeastern dissected edge of plateau uplands that eventually merge with the contiguous High Plains, which extend east of the Rocky Mountains from Texas and New Mexico into Alberta, Canada. The Blackland belt extends beyond Central Texas, skirting the entire Gulf Coastal Plain and Mississippi Embayment through Arkansas, Mississippi, and western Alabama. TIle Blacklands are prime cotton country, and in Texas these deep, fertile, black soils encouraged a cultural transplant of the Old South. West of the Balcones Escarpment, in contrast, traditional land use has been ranching; farming is limited largely to arable stream bottoms. In brief, the cultural outlook from the Blackland Prairies is southern; from the edge of the Great Plains west of the Balcones Escarpment, the cultural sense is western.

The Balcones Escarpment was so named because of its functioning as a physical barrier: an overlook wi thout ready access from below--the balconies. This physical barrier was used to good advantage during the cattle drives up the Chisholm Trail. Fertile grasslands and perennial, spring-fed streams lay adjacent to the hilly terrain that hemmed in the herds on one side. But even before the time of the cattle drives, the Balcones Escarpment was already a prime area for human habitation. Archaeological surveys have documented sites along the escarpment that were occupied by Paleo-Indians as early as [[ ,000 years ago (Hester, [986). Subsequent archaeological sites cluster along the escarpment, suggesting that the dependable water supplied by springs was a major resource for early man. The springs also proved to be an understandable attraction to European settlers; in the early eighteenth century, the Spanish located their missions and presidio at Bexar (San Antonio) because of the springs that fed the headwaters of the San Antonio River. Later, in the m,id-nineteenth century, German colonists settled in the New Braunsfels area because of the rich soils to the east and the high yield springs flowing from the base of the hills. Still later, M. B. Lamar, President of the Texas Republic, and a westward looking exponent of Manifest Destiny, chose Waterloo (later to be renamed Austin) as the new Capital of the Republic. This choice was made expressly because the site lay on the threshold of the West and because the key natural resource for a successful settlement did exist--namely water. The water was there in abundance for exactly the same reasons as the dramatic landscape changes: a geologic fault zone controlled the topographic and hydrologic setting.

Notwithstanding such western visions, the area west of the Balcones Escarpment remained virtually unsettled until well into the Nineteenth Century. That region remained the undisputed realm of the Comanches and Apaches until the 1840's (Palmer, 1986). Only after the American Civil War did civilization come to the Hill Country and Edwards Plateau, and then

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the conversion occurred only haltingly. Rose (1991) has pointed out how the dissected margins of the Edwards Plateau promoted the continuation of frontier lawlessness: The Plateau uplands provided open land for long-distance surveillance and for rapid movement by mounted raiders--both outlaws and Indians--whereas the incised headwater canyons provided refuges for hideouts and defense. Ultimate settlement and civilization of the Edwards Plateau (as well as the rest of the Great Plains) depended on widespread employment of three technological advances: the windmill, barbed wire, and the six shooter (Webb, 1931).

GEOLOGIC SETTING The Balcones Escarpment marks the line of main dislocation across the Balcones Fault

Zone, which comprises an en-echelon system of mainly down-to-the-coast normal faults. Total displacement across the fault zone is at least several thousand feet, and individual faults have displacements of about 1,000 ft, although many faults composing the system have displacements ranging from a few feet to tens of feet. The Balcones Fault Zone is aligned along an overall northeast-southwest orientation; in detail, however, local small-displacement faults trend in various directions. In sum, Lower Cretaceous limestones are juxtaposed against Upper Cretaceous claystones, chalks, and shales. The relatively soft claystones and shales east of the main fault line have been eroded more rapidly than the limestones to the west; hence, the areas of limestone bedrock have been sculpted into a rugged hilly terrain, whereas the softer claystones form low rolling prairies. In this way, the geologic break has resulted in the abrupt change in landscape. In detail, faulting has created a mosaic of different rock types that results in varying local ground conditions.

The Balcones Fault Zone is a near-surface manifestation of a more profound, deep-seated geologic break: Beneath the fault zone, the buried roots of the Ouachita Mountain Belt mark the boundary between the continental interior of North America and the still-subsiding Gulf Coast Basin. The Ouachita Mountains once stood tall through Central Texas, but the complex now extends underground from their present southwestern edge in Oklahoma, south along a trend beneath DallasfFort Worth, Waco, Austin, San Antonio, to the Rio Grande near Del Rio. From there, the complex extends westward into Trans Pecos Texas and into Mexico in the Big Bend region. This complex belt originated owing to a collision (or close encounter) between the North American continent and parts of South America or Central America during the late Paleozoic Era (some 300 million years ago). Subsequently, about 250 million years ago, the Gulf of Mexico began to form when the continental blocks broke up and drifted apart. In Central Texas, the mountains were eroded and subsided below sea level and were covered by younger sediments that compose the Mesozoic strata across the hinge zone. The arcuate shape of the fault zone and the coastward-protruding escarpment reflect the underlying structural salient where the Ouachita belt bends around the Llano Precambrian massif. The areal location and depth of the Ouachita complex is documented owing to numerous deep wells and by various geophysical data. Balcones faulting was probably a result of periodic adjustments across this buried hinge.

A major episode of faulting along the Balcones trend occurred during the late Early Miocene (Young, 1972) as evidenced by reworked Cretaceous fossils in the t1uvial sandstones of the Oakville Formation (Wilson, 1956; Ely, 1957). This period of Balcones faulting is generally contemporaneous with the pervasive uplift and crustal extension associated with Basin and Range mountain-building episodes in Western North America. The Balcones Fault Zone thus marks a possible eastern boundary for this realm of major Cenozoic extensional tectonics. Hence, in yet another way, the fault zone and escarpment marks a dividing line between east and west.

The Oakville Formation contains so many Cretaceous fossils that early geologists thought it was the site of upfaulted Cretaceous strata. It is an anomaly within the Coastal Plain, which otherwise consists largely of quartz sandstones and muddy sediments. The Oakville Formation, in contrast, is a sandstone consisting of locally abundant limestone clasts. It is

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exposed today along the middle Gulf Coastal Plain and extends along an outcrop belt that parallels the present coast line from the vicinity of the Brazos River near Navasota, through LaGrange, and ending near the Karnes/Bee County Line in South Texas. The presence of reworked limy materials in this area has resulted in exceptionally fertile soils on rolling terrain similar to the Blackland Prairie. In brief, eroded, transported, and redeposited limestone fragments provide a means for establishing the age of the structural upheavals along the Balcones Fault Zone. Likewise, these reworked sediments result in a recurrence of the prairie terrain found at the foot of the Balcones Escarpment (Godfrey and others, 1973).

HYDROLOGIC SETTING AND RELATED PROCESSES West of the Balcones Escarpment, the limestone bedrock is resistant to erosion. Steep

slopes are the norm, and major through-flowing rivers locally course through deep narrow valleys. Accordingly, tributary streams exhibit steep gradients within sub-watersheds having high drainage densities. Soils are highly erodible on this hilly terrain. Soil formed erratically on this terrain to begin with, as limestone weathers chiefly by chemical dissolution, leaving little residue of sand, silt, and clay to form soils. Interlayered marly beds, in contrast, form locally thick soils. Long-term natural processes and recent land use have combined to result in significant soil erosion and redistribution of sediment in Hill Country watersheds; thick soils in alluvial valleys result largely from long-term erosion of the uplands. Elsewhere, across typical uplands of the Edwards Plateau and Hill Country, rocky soils less than a foot thick are common. Given ill-advised land-use practices, these thin soils may be stripped from the uplands by sheet runoff and gully erosion.

East of the escarpment, bedrock strata are more erodible. Consequently, the land is of lower relief with rolling prairie country and a less dense drainage network and lower stream gradients. Major streams meander back and forth across broad valleys cut in the soft bedrock, and extensive sheets of river laid sand and gravel cover parts of the Blacklands as a result of this process. The Blacklands, in contrast to the Hill Country,are noted for their uniformly thick, fertile soils. The claystone substrate and the gentle slopes combine to enhance these soil conditions, although adverse land practices can result in severe soil erosion across the Blacklands just as in the Hill Country.

The Balcones Escarpment is a major influence on climate. West of this line, the climate is drier year-round and somewhat cooler in the winter. But more important than the average temperature and rainfall values, the escarpment is a notorious weather maker. This break in the landscape generally has a relief of only a few hundred feet, but it is the first topographic barrier inland from the Gulf of Mexico. Unstable, moisture laden Gulf air masses are forced to rise at the escarpment. In so doing, they cool and produce phenomenal storms. One of the largest rainfall events ever recorded in the conterminous United States occurred just east of the Escarpment near the Blackland community of Thrall, Williamson County, in September, 1921. At that time, more than 38 inches of rain fell in a 24 hOllr period-- compared to a usual annllal rainfall rate in Austin of about 32 inches. Other storms have produced record rainfall rates for shorter periods of time. The D'Hanis Flood of 1935, for example, resulted from 22 inches of rain in 2 hours and 45 minutes (Baker, 1975). In short, the area along the Balcones Escarpment is a zone of climatic hazard: it is the area of highest probability of large, flood­producing storms in the country (Hoyt and Langbein, 1955). The Hill Country is especially prone to flooding, owing to the coincidence of extreme rates of rainfall, steep slopes, and a large number of small, high-gradient streams (Caran and Baker, 1986). During heavy rains. streams can rise in a matter of minutes and be transformed into murderous torrents.

Groundwater availability abruptly changes across the Balcones Escarpment. On the west, several water-bearing rock formations (aquifers) occur at relatively shallow depths. On the eastern side of the Escarpment, however, these water-bearing strata are downfaulted to slich depths as to make drilling wells in the Blacklands a more expensive and risky venture. Commonly, the deep groundwater east of the escarpment is brackish and tepid. It seems ironic

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that the prime prairie cropland has an insecure groundwater supply, while the Hill Country with its rocky, less arable land, has ample groundwater at a reasonable depth. Of the water-bearing units along the Ba1cones Escarpment, the most important is the Edwards Limestone aquifer. It supplies drinking water to more than one million people, including the City of San Antonio, the largest city in the United States dependent entirely on groundwater for its source of municipal supply. It is also habitat to a variety of aquatic animal and plant species found nowhere else in the world. Moreover, the Edwards aquifer has played an important role in the evolution of the landscape along the Balcones Escarpment.

COEVOLUTION OF THE LANDSCAPE AND THE EDWARDS AQUIFER

Fundamental to the development of the Edwards aquifer and the Ba1cones Escarpment is the fact that the aquifer host rock is limestone and thus is soluble in water. For this reason, the development of the aquifer and the Ba1cones Escarpment is intertwined. The processes that formed the escarpment abetted bedrock dissolution, and thus created cavernous porosi ty for the aquifer. Likewise, aquifer development diverted water via subsurface now, thereby modifying surface erosion across the landscape. In brief, the coevolution of aquifer and escarpment involves the interactions between water and rock through space and time. Past geologic processes have shaped the rocks and landforms and the processes that are seen today. As already noted, the main orientation of faults composing the Ba1cones trend is northeast­southwest. This fault geometry controlled the orientation of the escarpment. It also continues to control groundwater now, in that faults locally act as baffles, retarding groundwater across them, whereas elsewhere, faults provide conduits for groundwater now. Evidence for both processes is seen in the overall recharge/discharge geometry-- with recharge occurring southwest of the major points of discharge. These processes are indicated by the geometry of sink-holes and caves, which are commonly aligned along faults and create zones of rapid recharge and water transmission.

The coevolution of the Ba1cones Escarpment and the Edwards aquifer involve water/rock interactions over three time periods: (I) the deposition of the Edwards Limestone; (2) the activation of the Balcones Fault Zone; and (3) drainage development during the relatively recent geologic past.

The first phase of the water/rock interactions was the deposition of the Edwards Limestone. The Edwards was laid down almost 100 million years ago in a warm, shallow sea (Rose, 1972). The setting was similar to the modern Bahama Banks or the Gulf of Campeche. A number of different environments were present: open marine as evidenced by the fossilized clams, snails, and other mollusks; cays and shoals and lagoons, as indicated by petrified palm and mangrove wood, and by fossil mud cracks and by collapse zones. The presence of evaporite minerals (anhydrite, gypsum, and the like), which were subsequently leached out producing the pervasive collapse zones suggest that there were extensive tidal flats periodically exposed to the air and sun. This evidence indicates that the environment was rather arid.

Cavernous porosity began to form almost immediately, as soon as the limy sediments hardened into rock--a process that may take only a relatively short period of time. A long shoals and cays, or wherever the rock was exposed, rainwater began etching the newly formed limestone, leaching soluble salts, and forming small caverns. Local collapse occurred. Already, this limestone was becoming an incipient aquifer. Similar conditions may be seen today where sinkholes and caves have formed in recent (Pleistocene) limestones along the shores of the Bahamas and Jamaica, for example.

During the time that the Edwards Limestone was deposited, the sea continued to encroach on this incipient aquifer, however, and more sediment was deposited on top of the initial cavernous zones. Eventually, all of Central Texas lay beneath the Cretaceous sea. Several hundred feet of mud and ooze blanketed the limestone that would one day become the Edwards aquifer. Although the pores within the rock were filled with water, no further solution could

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occur because the pore waters rapidly became chemically saturated with calcium dissolved from the limestone. For a karst aquifer to operate--for the rock to continue to be dissolved--there must be a dynamic through-flowing water system. Recharge must operate in one area and discharge in another, so that the water is continually flushed through the rock. Such conditions could not occur while the rock lay beneath hundreds of feet of sediments under scores of feet of sea water. So after the host rock was buried, aquifer development was arrested for tens of millions of years.

One of the most intriguing insights to this early cave development and the long period during which burial and stasis occurred is provided by the research on organisms living today within the waters of the Edwards aquifer. This research is being carried out by Dr. Glen Longley and colleagues at the Edwards

Aquifer Research and Data Center at Southwest Texas State University (Longley, 1986). Among the life forms collected are blind crawfish, and catfish, and rare cave salamanders. But these all probably evolved fairly recently from fresh-water species indigenous to the Hill Country. There are, however, also amphipods--tiny shrimp-like crustaceans--living within the brackish water of the bad-water zone of the Edwards. The closest living relatives of these animals are found in the Mediterranean littoral. In other words, the amphipods that are living today in the Edwards aquifer may be descended from marine organisms that existed in those early Cretaceous seas--when the Gulf of Mexico and the Atlantic Ocean were fairly young, and not too wide. Could it be that these creatures survived (and evolved) within the brackish limestone pore waters, while their relatives in the Mediterranean continued to live in a marine habitat?

Near the close of the Mesozoic Era, about 65 million years ago, the North American continent was uplifted. Cretaceous seas receded. By whatever gradual or cataclysmic process, the dinosaurs became extinct. The Rocky Mountains formed, and new rivers drained from these ranges across newly exposed landscapes. Giant deltas formed in East Texas--on a scale similar to that of the modem Mississippi. But the Edwards Limestone still lay buried, and the Balcones Escarpment was yet to be formed. Some deep circulation of pent-up groundwater may have occurred; but little additional aquifer development was likely at that time. The aquifer system was still closed and largely stagnant. Late Cretaceous volcanoes were emplaced along the inner Coastal Plain as precursors of Balcones faulting (Ewing and Caran, 1986). Some of these breached the seafloor and formed volcanic atolls. Pilot Knob, in South Austin, is such a feature.

Major terrain alteration and aquifer development were initiated only after the main Balcones Fault events of the Miocene Epoch (probably about 10 million years ago). Some minor movements along the fault zone probably occurred periodically as a result of ongoing adjustments across the Ouachita hinge. But progressive subsidence of the Gulf Coast Basin finally resulted in a critical threshold of stresses producing rupture and dislocations across the hinge. The coastward (eastern) side of the hinge was shunted down with respect to the continental interior. In this way, the area that was to become the Hill Country/Edwards Plateau was uplifted with respect to the Coastal Plain. Bedrock was tilted toward the coastline, which lay near what is now laGrange, in Fayette County. Only since this major episode of faulting (relatively recently in a geologic context) has the Edwards aquifer as we know it developed.

Because the western side of the of the fault line was up-lifted, increased erosion occurred there. Surface streams rapidly cut down through the soft strata overlying the Edwards Limestone, at which point the natural erosive processes had to adjust to the hard, thick, and extensive bedrock. The eventual result was the formation of the Edwards Plateau, which is capped by the resistant Edwards Limestone. Meanwhile, when the Edwards Limestone was unearthed, there were--for the first time in millions of years--points for egress of pent-up groundwater. Further erosion resulted in exposure of the Edwards across a general upland terrain, providing a means for the continuous circulation of waters that we see today, with recharge in one area,underground flow with associated dissolution of the host rock, and

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discharge at springs. All these processes were part of dramatic changes in the Central Texas landscape associated with Balcones faulting.

In brief, Balcones faulting provided the impetus for erosion by surface waters that exhumed the aquifer host rock. This, in turn, resulted in through-going transfer of waters accompanied by flushing of calcium-saturated pore water, and the addition of new, fresh rainwater capable of dissolving more limestone. Besides providing the erosional impetus responsible for "opening up the aquifer," faulting provided fractures that were later enlarged by solution. In this way, some of the faults became major avenues for underground flow. In places, rock units having dramatically different permeabilities were juxtaposed, and there, faults acted as baftles retarding flow across them. As a result of these various processes, the aquifer was compartmentalized into discrete zones of preferred flow along northeast-southwest trends. The aquifer continued to develop in concert with the overall lowering of the landscape, with preferred directions of flow imposed by fault geometry. The subsequent sculpting of today's landscape is mainly the result of running and percolating waters acting over vast amounts of time to dissolve and erode soils and rock. The products of weathering and erosion have been (and continue to be) carried to the sea as coarse sediment, as suspended load, and as ions in solution.

After being exhumed by downcutting streams, the Edwards Limestone formed the caprock for a highland west of the Balcones Fault line. This early Edwards Plateau extended initially from Central Texas west into the Trans Pecos country and north into the Panhandle. Streams coursed across this ancient upland: ancestral versions of the Colorado, the Guadalupe, the Medina, the Nueces, and their tributaries. These streams cut valleys, and the tributaries etched the edges of the plateau. The courses of these streams, however, were markedly different from those seen today. Examination of a map shows that the headwaters of the main drainage course of the Guadalupe, Blanco, and Medina Rivers, and Cibolo Creek is roughly eastward. In contrast, immediately upstream from the fault zone, an abrupt change in course coincides with the incised canyon-like reaches of these streams. The ancient courses of these streams probably continued to the east, and all may have been tributaries within an early Colorado River drainage system. The abrupt changes in stream courses were probably results of fault geometry, which induced diversion of surface drainage.

Faulting provided new impetus for erosion. Initial slope breaks along the fault line provided sites for small, high-gradient streams to erode rapidly at right angles to the formative scarp. Steep canyons that today are the courses of the main trunk streams where they cross the fault zone may have been formed initially by minor tributaries that cut through the resistant Edwards cap and incised into the softer strata below. Eventually, by means of this headward erosion, these tributaries intersected the major through-tlowing drainageways and diverted their flow. In this way, the process of river diversion, or stream piracy, provided shorter and steeper routes to the sea.

The abrupt changes in course and canyon-like valleys near the Balcones Escarpment suggest sites where the initial piracy events occurred. Besides geometries of stream nets and the locations of incised valleys that support this piracy thesis, there are also relict features--both remnant gravel deposits and ancient scars of abandoned stream channels--isolated high on drainage divides far above the courses of modern streams. These relict features occur along probable ancient (pre-piracy) stream courses (Woodruff, 1977; Woodruff and Abbott, 1979). Similarly, extensive gravel deposits cap hills and divides across the Coastal Plain. These deposits provide evidence for reconstructing the former courses of rivers, since diverted by piracy episodes of various ages.

Stream Piracy was a major process affecting both the Edwards aquifer and the terrain along the Balcones Escarpment Pirate streams suddenly acquired a greatly enlarged drainage system and thus an enhanced ability to erode. With this newly acquired tlow, these streams cut deeply into the limestone terrains up-lifted by Balcones faulting. Evidence for this is seen today not only in the narrow incised valleys, but in the general dissection of the Hill Country by myriad

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surface streams. Furthermore, localized downcutting within the initial courses of the pirate streams provided openings in the aquifer at the lowest topographic levels in the region. These low areas became the sites of springs, which acted as drains for the aquifer. Notably, major springs occur where trunk streams cut across the Balcones Escarpment: Comal Springs near the Guadalupe River; San Marcos Springs near the Blanco River; and Barton Springs near the Colorado River. Only San Antonio and San Pedro Springs seem to be exceptions, and they may lie near a former course of Medina River that has since been diverted farther west.

Rivers of the Nueces River Basin show no such evidence for major piracy. The geometry of drainage networks trends generally north-south, roughly perpendicular to the cscarpment in that extensive watershed. There are no known relict alluvial features on the high divides in the Nueces watershed. Hence, piracy was probably not a major process there, and as a result stream incision was less vigorous. Today this basin stands at the highest topographic level of any along the Balcones Fault line; and it is the prime recharge zone for the part of the aquifer that provides water to Comal Springs and San Marcos Springs and the huge well fields supplying urban San Antonio. It seems to be another of Nature's ironies that these western watersheds, where rainfall is meager to begin with, subsidize the wetter eastern Guadalupe and San Antonio River basins by the underground long-distance transfer of water. For the central aquifer segment, 55 percent of total recharge occurs in the Nueces basins, while only 9 perccnt of the discharge occurs there. The Guadalupe basin accounts for only 13 percent of the recharge but produces 59 percent of the discharge--mostly from Comal and San Marcos Springs.

A similar example of the influence of piracy on recharge/discharge geometry is seen on a smaller scale in the Barton Springs segment of the aquifer (Woodruff, 1977; 1984). Evidence suggests that the Blanco River and Onion Creek once formed a single eastward-trending watershed (flowing into Colorado River). However, headward erosion and piracy diverted the headwaters of this integrated steam network into what is the present course of Blanco River. The deep erosion along the course of the pirate stream resulted in the establishment of San Marcos Springs; while the beheaded Onion Creek system had a diminished erosive power and thus remained at a relatively high topographic level. Thus, it is a prime recharge area for waters draining toward Barton Springs. On the other end of the Barton Springs segment. near the Colorado River and the springs themselves, another episode of piracy likely occurred: the lower reaches of Barton Creek may be part of an incised pirate stream. The former Barton Creek system probably flowed across what is now the Williamson Creek watershed and deposited the extensive Saint Elmo Terrace that today underlies Ben White Boulevard in South Austin and stretches along the Williamson Creek drainage divide from the Sunset Valley area east almost to Bergstrom Air Force Base. After capture by the incised stream, the headwaters of Barton Creek were diverted to the vicinity of Barton Springs. As a result, the Williamson Creek watershed remains a relatively undissected upland, while across the drainage divide, Barton Creek has cut down vigorously through canyon-like areas upstream from the springs.

SUMMARY AND CONCLUSIONS

In summary, abrupt bedrock changes across the Balcones Fault Zone with their ancient. deep­seatcd controls continue to dramatically affect almost all other attributes of the land: terrain, soils, vegetation and animal habitat, surface-water and groundwater availability, weather, and all water-related processes. These environmental changes, in turn, have interacted to affect human endeavors in profound ways. The Balcones Escarpment separates the cotton culture of the Old South from the rangelands and the cattle economy of the Old West (Bybee, 1952; Flawn, 1964). The geologic fault zone thus also marks a cultural fault. Walter Prescott Webb, in his classic treatise, The Great Plains (Webb, 1931), denoted the beginning of the American West at the 98th meridian. His perspective for drawing this line was his Friday Mountain Ranch in the Hill Country near the TravislHays County Line. This ranch lies a few miles east of the 98th Meridian, but it is also bisected by the Mount Bonnell Fault, which is the main fault

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of the Balcones system in the Austin area. On the basis of the sum of changes across the BalconesiOuachita discontinuity -- geological, ecological, and social--the Balcones Escarpment provides a physical boundary between East and West. It is the meeting of the prairies and the plains.

REFERENCES Baker, Y.R.

1975 Flood hazards along the Balcones Escarpment in Central Texas; alternative approaches to their recognition, mapping, and management: The University of Texas at Austin, Bureau of Economic Geology Circular 75-5, 22 p.

Bybee, H.P. 1952 The Balcones Fault Zone--an influence on human economy: Texas Journal of Science.

v. 4, p. 387-392. Caran, S. C., and Baker, Y. R.

1986 Flooding along the Balcones Escarpment, Central Texas, in Abbott, P. L, and Woodruff, C. M., Jr., eds., The Balcones Escarpment--geology, hydrology, ecology, and social development in Central Texas, published for Geological Society of America Annual Meeting, San Antonio, Texas, November, 1986, p. 1-14.

Ely, L.M. 1957 Microfauna of the Oakville Formation, LaGrange area, Fayette County, Texas: The

University of Texas (Austin), M.A. thesis (unpublished), 118 p. Ewing, T. C., and Caran, S. C.

1982 Late Cretaceous volcanism in South and Central Texas--stratigraphic, structural, and seismic models: Gulf Coast Association of Geological Societies Transactions, v. 32. p. 137-145.

Fenneman, N.M. 1931 Physiography of Western United States: New Your, McGraw-Hill, 534 p.

Flawn, P.T. 1964 The everlasting land, in Maguire, Jack, ed., A President's Country, Austin, Shoal

Creek Pub1ishers,84 p. Godfrey, C.L., McKee, G.S., and Oakes, H.

1973 General soil map of Texas: Texas Agricultural Experiment Station, Texas A&M University; approximate scale, 1 :500,000.

Hester, T. R. 1986 Early human populations along the Balcones Escarpment, in Abbott, P.L., and

Woodruff, C.M., Jr., eds., The Balcones Escarpment, Geology, Hydrology, Ecology and Social Development in Central Texas, published for Geological Society of America Annual Meeting, San Antonio, Texas, November 1986, p. 55-62.

Hoyt W.G., and Langbein, W. B. 1955 Floods: Princeton, Princeton University Press, 469 p.

Longley, G. 1986 The biota of the Edwards aquifer and the implications for paleozoogeography, in

Abbott, P.L., and Woodruff, C.M., Jr., eds., The Balcones Escarpment, Geology, Hydrology, Ecology and Social Development in Central Texas, published for Geological Society of America Annual Meeting, San Antonio, Texas, November 1986, p. 51-54.

Palmer, E.C. 1986 Land use and cultural change along the Balcones Escarpment: 1718-1986, in Abbott,

P.L., and Woodruff, C.M., Jr., eds., The Balcones Escarpment, Geology, Hydrology, Ecology and Social Development in Central Texas, published for Geological Society of America Annual Meeting, San Antonio, Texas. November 1986, p. 153-161.

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Rose, P.R. 1972 Edwards Group, surface and subsurface, Central Texas: The University of Texas at

Austin, Bureau of Economic Geology Report of Investigations no. 74, 198 p. 1990 Role of Edwards Plateau geology in prolonging era of frontier lawlessness, West­

eentral Texas, I 860-1 880:Austin Geological Society Newsletter. Webb, W. P., 1931, The Great Plains, Boston, Ginn (reprinted by University of Nebraska

Press, 1985), 525 p. Wilson, J.A.

1956 Miocene formations and vertebrate biostratigraphic units, Texas Coastal Plain: American Association of Petroleum Geologists Bulletin, v. 40, no 9, p. 2233-224

Woodmff, C.M., Jr. 1977 Stream piracy along the Balcones Escarpment, Central Texas: Journal of Geology, v.

, i !

85, no. 4, p. 483-490. I

1984 Stream piracy--possible controls on recharge/discharge geometry, Edwards aquifer. ! Barton Springs Segment, in

Woodmff, C.M., Jr., and Abbott, P.L. 1979 Drainage-basin evolution and aquifer development in a karstic limestone terrain, south­

eentral Texas, USA: Earth-Surface Processes, v. 4, no. 4, p. 319-334. Young, K.

1972 Mesozoic history, Llano region, in Barnes, V.E., Bell, W.C., Clabaugh, S.E., Cloud, P.E., Jr., McGehee, R.Y., Rodda, P.U., and Young, K., eds., Geology of the Llano region and Austin, area, Field Excursion: The University of Texas at Austin, Bureau of Economic Geology Guidebook 13,77 p.

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I I I

NEOGENE AND QUATERNARY STRATIGRAPHY OF THE INNER GULF COASTAL PLAINS, SOUTH-CENTRAL TEXAS

S. Christopher Caran Department of Geological Sciences The University of Texas at Austin

Austin, Texas 78713

INTRODUCTION Nonmarine Neogene (Late Miocene-Pliocene) and Quaternary

deposits compose an undeformed veneer manteling the thick down-faulted and downwarped Upper Cretaceous (Gulfian), Paleogene, and Lower Miocene stratigraphic sequence of the Inner Gulf Coastal Plains of South-Central Texas. Fluvial sands and gravels, reflecting both ancient and modern drainage systems, constitute a majority of Neogene and Quaternary sections throughout the region. Other sediment types are represented locally, however, including alluvial­fan deposits, peat, and a variety of pedogenic and diagenetic sediments. The Balcones Escarpment, which forms the western and northern boundaries of the Inner Gulf Coastal Plains, provides a complementary record of this period, including subaerial and subterranean travertines, clastic cave fills (some of which contain important paleofaunas), collapse breccias, and mass-movement deposits, as well as fluvial­terrace fills.

In the past, chronologic control in Neogene and Quaternary sections of the Inner Gulf Coastal Plains was primarily based on qualitative evidence such as paleofaunal and geomorphic indicators (landscape position, integrity and continuity of deposits, degree of soil development, etc.). No faunas older than Rancholabrean (~8,OOO-300,OOO yr) are known from the Coastal Plains west of peninsular Florida, however, and there were few calibrated geomorphic records. The available data helped provide a relative-age sequence, yet lacked the precision and resolution required for detailed assessments. Radiocarbon assays were used sparingly, but were limited to dating deposits of Holocene and latest Pleistocene age. The absence of a quantitative chronometry for strata that pre-date the effective limit of radiocarbon extinction (~50,OOO yr) and/or lack materials suitable for other numerical dating methods was a major hinderance to investigation of Neogene and Quaternary deposits throughout the entire Gulf Coastal Plains.

Recent studies at a site in southern 8astrop County, Texas, provided the first quantitative age determinations for deposits falling within the previously undatable "window" from Late Miocene to Late Pleistocene in this region. Tephrochronology, supported by paleomagnetic analyses and earlier paleofaunal evidence from correlative deposits, demonstrates an Early to Middle Pleistocene age for the fill of the Capitol Terrace, one of the upper terraces of the Colorado River. This evidence affords a means of interpolating ages of younger terraces fills, helps to

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constrain the age of older fills, and provides a temporal benchmark for gauging rates of landscape evolution across the region.

PHYSIOGRAPHIC, STRUCTURAL, AND STRATIGRAPHIC SETTING The Gulf Coastal Plains is a broad, low-relief, gently

sloping terrain separating the Great Plains physiographic province of the continental interior from the Gulf of Mexico, a partially restricted arm of the Atlantic Ocean (Fenneman. 1946). The present study focusses on that portion of the Inner Gulf Coastal Plains in South-Central Texas, an area ~50 to 75 mi (80 to 120 km) wide along and coastward from the Balcones Escarpment, the boundary between the Edwards Plateau of the Great Plains and the Blackland Prairie of the Gulf Coastal Plains (see Guidebook Fig. 1). Several major rivers cross this zone on their way to the Gulf of Mexico, such that the study area includes parts of the Nueces, San Antonio, Guadalupe, and Colorado drainage basins, stretching from the Colorado-Brazos drainage divide in the northeast to near the Nueces-Rio Grande divide in the southwest. The study area generally corresponds to the Upper Cretaceous, Paleogene, and Miocene bedrock terranes, although fault blocks of Lower Cretaceous bedrock units are incorporated locally. Division of the Gulf Coastal Plains into inner and outer segments is somewhat arbitrary, but the boundary is here placed at the contact between the Pliocene nonmarine Willis Formation and the Pleistocene marginal marine Lissie Formation. This contact roughly defines the coastward limit of the present study area.

The Inner Gulf Coastal Plains of Texas are bounded on the north and west by the Balcones Escarpment, a prominent fault-line scarp coincident with the proximal edge of the Balcones Fault System (Woodruff, this volume). The Balcones Fault System comprises a series of normal faults, most of which were downthrown on their coastward sides. This system of faults lies within a zone of recurrent structural weakness at the edge of the North American Craton. Folded and thrust­faulted Paleozoic strata of the Ouachita-Appalachian Orogenic Belt lie deeply buried beneath this zone (Flawn et al., 1961). During Late Cretaceous time, igneous intrusion and volcanism (mafic to ultramafic compositions) was concentrated along this zone, as well (Ewing and Caran. 1982). In addition to the Balcones Fault System at the border of the Coastal Plains. numerous faults parallel the Escarpment at varying distances to the east and south. The extensive Luling Fault System consists of normal faults with antithetic displacements, which create an assymmetrical grabben through much of the Inner Coastal Plains (Weeks, 1945; Ewing. 1990).

The general pattern of relief now evident across the region is an indirect result of Balcones faulting. Differential sediment loading in the deepening Gulf of Mexico basin caused Upper Cretaceous and overlying Paleogene strata to be gently downwarped penecontemporaneous with deposition. The downwarped strata form a broad, low-angle, coastward-

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· . 1

) dipping monocline (Fig. 1). During the Late Miocene, these same strata were faulted, down dropped, and further rotated across the high-angle normal faults of the 8alcones Fault System. The style and timing of 8alcones faulting and the general orientation of the faults closely corresponds to that of the 8asin and Range extensional regime (Ewing, 1991: 28-29). Gable and Hatton (1983: Map 1) indicate that the net epeirogenic uplift of the Edwards Plateau area during and following the Late Miocene was as much as 1600 ft (500 m), which would account for the total offset across the fault zone. Upper Cretaceous strata in this region are relatively unconsolidated, chiefly consisting of marls. 8alcones faulting brought these marls into contact with indurated Lower Cretaceous limestones and dolostones. The 8alcones Escarpment was created by preferential erosion of the marls and related strata long after tectonic displacement ended.

Formations cropping out across the Inner Gulf Coastal Plains primarily consist of: Upper Cretaceous open marine and lagoonal marls, limestones, and shales, with mafic to ultramafic intrusions, tephra, and flows; Paleocene shallow marine shales; Eocene marine, paralic, and nonmarine sandstones and shales with seams of lignite; Oligocene shales and sandstones, locally incorporating volcanic tephra; and Miocene sandstones and conglomerates, in part composed of lithoclasts of Cretaceous limestone. Upper Cretaceous rocks are confined to the proximal margin of the Coastal Plains, mostly within the 8alcones Fault Zone. Eocene deposits are particularly thick, lithologically variable, and laterally extensive in outcrop. All of these strata are unconformably overlain by a complex suite of Neogene and Quaternary deposits, described below. Most of the bedrock units were sediment sources far younger deposits and some formed permeability barriers along which diagenetic sediments accumulated.

NEOGENE AND QUATERNARY STRATIGRAPHY A diverse group of Quaternary and Neogene strata is

exposed across the Inner Gulf Coastal Plains of South-Central Texas. These deposits vary temporally, geographically, in relation to substrate (subjacent bedrock) and geomorphic context, and with respect to post-depositional modification through erosion, burial, pedogenesis, Or diagenesis. The degree to which deposits in different areas are correlative remains largely uncertain. It is seldom clear whether terrace fills in one drainage basin can be accurately correlated with those of another basin. Age control may assist correlation, but contemporaneous deposits are not necessarily correlative. Even within a single basin, terrace fills in separate reaches may have been deposited simultaneously, yet differ in style or local environment of deposition. Lateral accretion may occur at a given point bar during the same flood event that cuts and refills a chute through older flood-plain deposits, and causes vertical accretion on a flood terrace. Conversely, a terrace may

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extend down-valley continuously, yet be everywhere diachronous.

Such variations should, in fact, be the rule, rather than the exception, because lateral accretion implies that both cross-valley and down-valley aggradation are progressive and therefore diachronous. Only extreme high-magnitude floods are likely to produce widespread contemporaneous vertical accretion of overbank deposits, but these too will vary as flood stage is enhanced or attenuated in response to channel geometry, gradient, and obstruction, or the width and slope of flood plains and flood terraces in different reaches. Adjacent basins or nearby reaches in a single basin are unlikely to feel comparable effects even during the highest flood of record; for example, it is uncommon for different gaging stations to have attained their respective highest stages or discharge rates during the same storm event, even when the stations are nearby in the same drainage basin.

8aker (1975), Caran and 8aker (1986), and 80mar (this volume) discussed the localized nature of flood-producing storms in this region. Under a less erratic flow regime, which might have existed during previous climatic episodes, there may have been somewhat greater consistency in the discharge patterns and in the resulting sedimentary sequences of different reaches or basins. It. is probable, however, that such episodes of consistency, if they existed at all, were so short lived that their sediment records were volumetrically insignificant. This does not mean that the range in age of a given deposit or series of deposits cannot be determined; instead, discretion is needed to assess the applicability of data from different locations. The same arguements may apply to other types of Neogene and Quaternary deposits in the region, as well.

Miocene Deposits Q~~~~ll~_~~c~~t~~~

The oldest Neogene deposits recognized in the Inner Gulf Coastal Plains are, from oldest to youngest, the Oakville, Fleming, and Goliad Formations, of Miocene age. The Oakville Formation is a gravelly sandstone and shale overlying Oligocene Catahoula sandstones. Locally, the Oakville contains mineable concentrations of uranium. Much of the Oakville is heavilly cemented with calcium carbonate, making these deposits highly resistant to erosion. As a result, they stand in relief as a west-facing cuesta, the largest of which is the 80rdas Escarpment of South Texas. The Oakville is the oldest formation that is composed in part of lithoclasts of Lower Cretaceous limestone, including diagnostic marine fossils. The presence of these lithoclasts is significant because it proves that by the time of Oakville deposition, Lower Cretaceous strata of the Edwards Plateau had been exposed to erosion following the 8alcones faulting. It is, therefore one the lines of evidence establishing the approximate time of faulting. Oakville strata have yielded

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vertebrate remains that establish the age of this formation as Early Miocene (Wilson, 1956).

El~m~ug_EQcm~t~QU The Middle Miocene Fleming Formation is the thickest and

most areally extensive of the Miocene deposits in the Inner Coastal Plains. The Fleming consists of shales and sandstones and, like the underlying Oakville Formation, contains lithoclasts of Lower Cretaceous limestone, as well as Miocene vertebrate fossils. The contact between the Oakville and Fleming is an erosional unconformity. Oakville and older strata dip downward into the Gulf of Mexico basin as a result of sediment loading on the Outer Coastal Plains and the Continental Shelf. Fleming deposits are more than 1200 ft (370 m) thick and no doubt contributed to the downwarp of subjacent strata. In contrast, deposits overlying the Fleming are so thin that they have caused little downwarp in Fleming and younger strata. Except along some faults, all of the Coastal Plains deposits have gentle dips (~5 degrees), but the dips of Fleming and younger strata typically are even lower.

Goliad Formation ------ ---------The Late Miocene Goliad Formation is the youngest of the

three Miocene units in the region. Lithologies characteristic of the Goliad include shales, sandstones, and conglomerates. In places, this formation is highly calcareous, as a result of pedogenic and/or near-surface diagenetic enrichment. Cementation makes the formation resistant to erosion, such that it crops out as a series of low ridges and cuestas. The age of this formation has long been in question because few vertebrate remains and other temporal indicators had been found. Recent studies reported by Tedford and others (19B7, Pl. 6.2) have shown convincingly that the Goliad is Late Miocene.

Pliocene Deposits ~illi§_EQIm~!iQ~

Two nonmarine Pliocene deposits are generally recognized in the Inner Gulf Coastal Plains, but there are several possible Pliocene deposits, as well. Virtually no vertebrate remains or other direst chronologic indicators have been found in any of these deposits. The Willis and the Uvalde Formations are usually considered Pliocene (see also Loomis ~t ~l., this volume) and are the most extensive--they are the only lithologic units in this part of the section that are accorded formation status (Table 1). The Willis Formation forms a nearly continuous outcrop along the coastward edge of the Inner Gulf Coastal Plains as here defined. Dominant lithology is gravel and sand, and the formation thickens to ~30 m (100 ft) to the southeast down the Coastal Plain paleo­dip surface. Dip of the Willis beds is low (~2 degrees), but steeper than that of Pleistocene I'coastwise " deposits such as the Lissie and Beaumont (Winkler, 1991, Pl. B).

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~Y~!Q~ EQ~~~~iQD The Uvalde Formation is perhaps the most often

misinterpreted stratigraphic unit in the region. Hill (1891, p. 368) defined the Uvalde Formation as an upland relict gravel capping drainage divides, and consisting of lithoclasts of chert and limestone derived from Lower Cretaceous formations of the Edwards Plateau, along with a small percentage of exotic clasts including quartzite and vein quartz. In the area where this formation was originally recognized, in the Nueces and San Antonio/Medina drainages, particularly in Uvalde and Medina Counties, the Uvalde is a valid stratigraphic unit and use of the name Uvalde is entirely appropriate (Table 1). [Participants in the 1992 South-Central Friends of the Pleistocene Field Trip will see an excellent exposure of the Uvalde Formation in Medina County.]

Some investigators, however, have misapplied the term elsewhere. This practice actually began with Hill himself (Hill and Vaughan, 1897) when he mapped upland gravels in the Austin area as Uvalde. The deposits mapped as Uvalde included: fill terraces along paleochannels of major tributaries of the Colorado River (Urbanes, 1963; Weber, 1968); and gravel lags lacking discrete stratigraphic correlatives. Later workers have incorrectly applied the name Uvalde to virtually every upland gravel, and even to high terrace fills, throughout the Texas Coastal Plains (e.g., Byrd, 1971). Part of the problem has to do with using a formation name for an unstratified lag deposit consisting of clasts assumed to have been derived from that unit, which is completely inappropriate. Such lags occur on surfaces across the region in unrelated geomorphic contexts, where there is no basis for correlation. In addition, the occurrence of exotic clasts, particularly quartzites, in gravel deposits seems to have encouraged use of the name Uvalde in some cases (e.g., Mathis, 1942). These clasts are extremely durable and are reworked through multiple generations of fills. [Field trip participants will find examples of these clast types at most of the stops in the Bastrop and Smithville areas.] Even the quartzite and other exotic clasts in the Uvalde Formation itself were reworked from older fluvial deposits, because there are no known primary (bedrock) sources of quartzite in any of the drainage basins of South-Central Texas. Although it is not possible here to present a complete review of the evidence contra­indicating correlation of these kinds of deposits with the Uvalde Formation. Yet there appear to be no clear examples of stratified fluvial gravels sufficiently high in the landscape to qualify as the Uvalde Formation north of the San Antonio River basin.

~ll~~l~l=f~Q Q~~~~lt~ Alluvial-fan deposits of varying age are found

throughout the region (Table 1). Those capping drainage divides of high-order streams may be as old as Pliocene, but are perhaps Early Pleistocene. Edwards (1974) described an

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extensive alluvial-fan system in the Brazos River basin just north of the Colorado-Brazos divide in Williamson County. Similar, but less extensive systems are represented in elevated sites across the Colorado and Guadalupe basins. Few of these deposits have been investigated; most are not even shown on published geologic maps. Small alluvial-fans are found in many places in the region and are demonstrably Pleistocene to modern.

Quaternary Fluvial Terrace Fills Valleys of each of the major drainage basins of the

Inner Gulf Coastal Plains in South-Central Texas have well­defined fill terraces. Investigation of these terraces has been uneven, however. Prior to studies conducted at the Applewhite Reservoir site on the Medina River, the only terraces that had been described systematically were those of the Colorado River, primarily in the Austin area (Table 1). For a detailed description of the Medina River terraces see Mandel (this volume). The Nueces and Guadalupe terrace systems are poorly known even now, and will not be discussed here.

The Colorado River terraces were first described by Hill and Vaughan (IB97). A number of later workers investigated aspects of terrace geomorphology, sedimentology, and soils (see reviews by Baker and Penteado-Orellana, 1977, and Blum, 1991), but made relatively minor revisions of Hill and Vaughan's original stratigraphic concepts. Confusion arose concerning topographically based definitions of the terraces and correlation with terraces downstream, resulting in unnecessary splitting and proliferation of terrace nomenclature. Terrace definitions were evaluated and reexamined using complete topographic-map (1:24,000 scale) coverage of that part of the Colorado drainage in the Inner Coastal Plains. Results of this review are shown in Table 2. Terrace names are not shown in this table if they were used for terraces that were conceptually and/or physically inseperable from those named previously. Terminology introduced by Blum (1991) is not treated in this review. Blum's findings concern only the lower terraces previously named Sand Beach, Riverview, First Street, and Sixth Street. His basis for establishing new terms is different from that used by previous workers, preventing direct comparison in the space permitted here. Terminology used throughout this volume follows that shown in Tables 1-3. The topographic (relief) ranges of Colorado River terraces in Austin, Bastrop, and Smithville are given in Table 2. Alternate terms appropriate for describing terraces in Bastrop and Smithville are provided in Table 3, along with the names of equivalent terraces in the Austin area.

SUMMARY Neogene and Quaternary deposits of the Inner Gulf

Coastal Plains are thick, laterally extensive, and lithologically variable, and may, in aggregate, be nearly

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continuous chronologically. Previous workers have shown that topographically separate deposits of a given area are often chronologically distinct, as well. The oldest deposits are generally those highest in the landscape. Erosion and structural downwarp have modified the landscape differentially, such that many of the deposits are relicts with limited continuity. Stratigraphic correlation depends on comparability of a range of characters. There has been significant recent improvement in understanding the chronology of these deposits, which will aid future efforts to develop a coherent regional stratigraphy.

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Table 1. Neogene (post-Willis Pliocene) and Quaternary stratigraphy of the Inner Gulf Coastal Plains, South-Central Texas.

PLIOCENE

River basins

Nueces San Antoniol Medina

Uvalde Formation ?

?

Guadalupe

alluvial­fan

?

Colorado

alluvial­fan

?

PLEISTOCENE deposits deposits*

HOLOCENE

"Walsh Terrace filII!

? ? ?

? ? Asylum

Leona Formation

fluvial terrace fills

flood­plain fi 11s

"Applewhite Fm. "**

HMi Iler Terrace fill"

?

fluvial terrace fi 11 s

flood­plain fills

Capitol*** Sixth St. First St.

Riverview Sand Beach

*These fans cap drainage divides and are analogous to the Taylor Fan of the Brazos River basin, just north of the Colorado-Brazos divide in Williamson County (Edwards, 1974). Small alluvial fans are found along the base of the Balcones Escarpment and in many Coastal Plains stream valleys, but the age of the smaller fans appears to range from Pleistocene to modern.

**Includes several paleosols (Mandel, this volume).

***Includes Lava Creek B volcanic ash (620,000 yr B.P.) at Rehmet locality; a magnetostratigraphic record has also been established at this site.

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Table 2. Relief of the Colorado River terraces in the

Terrace/ Relief above Colorado River (low-flow stage): as terrace reported previously (1-6); as described here (7-9) g~~~~it~ ___ l _____ g _____ ~ _____ i _____ ~ _____ ~ _____ Z _____ § _____ 2 __

Uvalde*

Asylum

Capitol

Montop­o I is

Sixth Street

First Street

River­view

Sand Beach

230-330

195-215

105-130 NR

80

60?

NR?

~10?

250 ~200-

279 160- 195-190 210

100 130-160

NR 75-90

75 60

24- 30-45 40

16- NR 28

NR NR

213-2BO

197-213

131-158 75-

92 59-

66 33-50

20-33 7-16

200+

180-197

100-130 NR

65-80

33-50

20-33 7-16

230+

197-213

131-157 75-

82 59-

66 33-

50 20-33 7-16

NR

180-210

100-130 NR

60-80

30-50

18-30 8-18

NR

190-230

100-155 NR

65-90

40-60

~25-

40 S25

NR

195-240

105-160 NR

65-90

40-65

~30-

40 S30

River 422 NR ~420 NR NR NR 422** 290- 270-__ ~l~~~ ______________________________________________ ~gQ ___ g§~

*The Uvalde Formation as defined by Hill (1895) "is not a Colorado River terrace, although many investigators have described and/or treated it as such. Furthermore, it is doubtful that the Uvalde exists as a discrete stratigraphic entity north of the San Antonio River basin (see text).

**The elevation cited is that given by Hill and Vaughan (1897, p. 244) for the low-flow river stage in central Austin. Longhorn Dam impounded the river in 1960, creating Town Lake, with a pool elevation of 428 ft. Elevation of the river in Austin below Longhorn Dam is ~400 ft.

NR = Not reported or not recognized

1: Hill and Vaughan (1897, p. 244, 248); ~~~ ~l~~ Hill (1901, p. 352) and Hill and Vaughan (1902).

2: Deussen (1924, p. 115-116) 3: Weber (1968) 4: Baker and Penteado-Orellana (1977, Table 1) 5: Looney and Baker (1977, Table 3) 6: Blum (1991, Table 6.5) 7-9: Relief as shown on the following topographic maps:

7--Austin East (Geological Survey, 1973a) and Montopolis (Geological Survey, 1973b); 8--Bastrop (Geological Survey, 1982) and Lake Bastrop (Geological Survey, 1982); 9--Smithville (Geological Survey, 1982) and Togo (Geological Survey, 1981).

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Table 3. Suggested nomenclature for correlative local terrace sequences, and numbers of stops at which respective terrace fills are exposed.

Asylum

Capitol

Si xth Street

First Street

Riverview

Sand Beach

State Park (3)

Red Bluffs (1,4,6)

Antioch (2)

Hills Prairie

Crafts Prairie

David Bottom

Stop 1 : Tiner gravel pit

2: Townsend gravel pit

3: Bastrop State Park

4: Red Bluffs

5: Tahitian Drive

6: Highway 71 gravel pit

7A: Rehmet locality

7B: Ferris gravel pit

8: Clark site

Buescher

Oak Hill (7A, 7B)

Colorado Community

Smithvi lie (8)

Shipp Lake

Hardeman Bend

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PUBLICATIONS RELATING TO THE QUATERNARY OF SIXTEEN COUNTIES IN THE CENTRAL TEXAS / BALCONES FAULT ZONE REGION:

A BmLIOGRAPHY

Dennis Trombatore

Walter Geology Library. The University of Texas at Austin. Austin. TX 787l3-7909

I l

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Abbott. Patrick L.. 1975. On the hydrology of the Edwards limestone. south­central Texas. Journal of Hydrology v.24. no.3-4. p.251-269.

Abbott. Patrick L. and Woodruff. C. M .• 1986. The Balcones Escarpment: geology. hydrology. ecology and social deyelopment in central Texas. Geological Society of America Annual Meeting Guidebook. Earth Enterprises. Austin. TX.

Alexander. W.H. and White. D.E.. 1966. Ground-water resources of Atascosa and Frio counties. Texas. Report no.32. Texas Water Development Board. Austin. TX.

Anders. RB .• 1957. Ground-water geology of Wilson county. Texas. Bulletin 5710. Texas Board of Water Engineers. Austin. TX.

Anders. RB .• 1960. Ground-water geology of Karnes county. Texas. Bulletin 6007. Texas Board of Water Engineers. Austin. TX.

Arnow. Ted. 1957. Records of wells in Travis county. Texas. Bulletin 5708. Texas Board of Water Engineers. Austin. TX.

Austin. Gene M .• 1954. Records of wells in Bastrop county. Texas. Bulletin 5413. Texas Board of Water Engineers. Austin. TX.

Baker. E.T. Jr .• 1986. Geohydrology of the Edwards Aquifer in the Austin area. ~. Report no.293. Texas Water Development Board. Austin. TX.

Baker. F.E. 1979. Soil Survey of Bastrop County. Texas. Soil Conservation Service. U.S. Dept. of Agriculture. Washington. D.C.

Baker. Victor R. 1975. Flood hazards along the BalcQnes Escarpment in central Texas. alternative approaches to their recognition. mapping and management. Geological Circular 75-5. Bureau of Economic Geology. Austin. TX.

Baker. Victor R. 1976. Arid-humid climatic change and altered fluvial regimen. Abstracts of the fourth biennjal meetjng of the American Ouaternary Association. p.40-41.

Baker. Victor R. 1977. Stream channel response to floods. with examples from Central Texas. Bulletin of the Geological Society of America. v.88. p.1057-1071.

Baker. Victor R 1983. Late Pleistocene fluvial systems in: Wright. H.E. and Porter. S.C .• eds. Late Ouaternary Environments of the United States: V.l The Late Pleistocene. University of Minnesota Press. Minneapolis. p. 26-41.

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Baker. Victor Rand Penteado-Orellano. M.M.. 1975. River adjustment to late quaternary hydrologic regimen changes in central Texas. Abstracts with Programs. Geological Society of America v.7 no.2 p.I44.

Baker. Victor Rand Penteado-Orellano. M. M. 1975. Sedimentology and paleohydrology of Quaternary fluvial regime changes. Colorado River. central Texas. Proceedings. Ninth International Sedimentological Congress. International Association of Sedimentologists. v.I. p.19-22.

Baker. Victor Rand Penteado-Orellano. M.M. 1977. Adjustment to late Quaternary climate change by the Colorado River of central Texas. Journal of Geology v.85 p.395-422.

Baker. Victor Rand Penteado-Orellano. M.M. 1978. Fluvial sedimentation conditioned by quaternary climatic change in central Texas. Journal of Sedimentary Petrology v,48 no.2. p,433-451.

Baker. Victor R. et al. 1973. Urban flooding and slope stability in Austin. Itl.a.s.. Fieldtrip Guidebook no.l. Austin Geological Society. Austin. TX.

Barnes. V.E. Geologic Atlas of Texas (scale 1:250.000): Austin sheet (1981. rev). Llano sheet (1981). San Antonio sheet (1983. rev.) and Seguin sheet (1974). Bureau of Economic Geology. Austin. TX.

Batte. Charles D .• 1984. SoU Survey of Comal and Hays Counties. Texas. Soil Conservation Service. U.S. Dept. of Agriculture. Washington. D.C.

Beck. Miles Walter. 1934. Soil Survey of Frio county. Texas. Soil Conservation Service. U.S. Dept. of Agriculture. Washington. D.C.

Bernard. H.A. and LeBlanc. R.J. 1965. Resume of the Quaternary geology of the northwestern Gulf of Mexico province. in: Wright. H.E .• Jr. and Frey. D.G. (eds.) The Ouaternary of the United States. Princeton Univ. Press. NJ. (reprinted in Bur. Eeon. Geol. guidebook 11).

Bernard. H.A .• LeBlanc. RJ .• and Major. C.F .• 1962. Recent and Pleistocene geology of the Gulf Coast and central Texas and guidebook of excursions. Geological Society of America. 1962 annual meeting. Houston Geological Society. Houston. TX.

Blair. W. Frank. 1950. The biotic provinces of Texas. Texas Journal of Science v.2. no.l. p.93-116.

Blum. Michael D.. 1987. Late <jpaternary sedimentation in the ppper Pedernales River. Texas. unpublished master's thesis. Univ. of Texas at Austin.

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Blum, Michael D. 1992. MQdern depositional envimnments and recent alluvial history of the Lower Colorado River. Gulf Coastal Plain of Texas. unpublished PhD dissertation, Univ. of Texas at Austin.

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Weeks, Albert W. 1941. Late Cenozoic deposits of the Texas coastal plain between the Brazos River and the Rio Grande. unpublished PhD Dissertation, Univ. of Texas at Austin.

Weeks, Albert W. 1945. Quaternary deposits of the Texas Coastal Plain between the Brazos River and the Rio Grande. Bulletin of the American Association of Petroleum Geologists. v.29, p.1733-1737.

Welder, F.A. and Reeves, R.D., 1962. Geology and ground-water resources of Uvalde county. Texas. Bulletin 6212, Texas Board of Water Engineers, Austin, TX.

Werchan, Leroy E., and Coker, J.L., 1983. Soil survey of Williamson county. Texas. Soil Conservation Service, U.S. Dept. of Agriculture, Washington, D.C.

Werchan, Leroy E., Lowther, A.C., and Ramsey, R.N., 1974. Soil survey of Travis county, Texas. Soil Conservation Service, U.S. Dept. of Agriculture, Washington, D.C.

Wilson, William Feathergail, 1982. Meteor impact site asphalt deposits and volcanic plugs: south Texas field trip 1981. in: Geology of the Llano Uplift central Texas and geological features in the Uvalde area. annual spring field conference. May 7-9, 1982. Corpus Christi Geological Society, Corpus Christi, TX. (separately paged).

Winkler, Alisa J., 1990. Small mammals from a Holocene sequence in central Texas and their paleoenvironmental implications. The Southwestern Naturalist v. 35, no.2, p.199-205.

Winston, R.A., 1907. Soil survey of Bastrop county, Texas. Soil Conservation Service, U.S. Dept. of Agriculture, Washington, D.C.

Wright, Thomas and Lundelius, Ernest Jr., 1963. Post-Pleistocene raccoons from central Texas and their zoogeographic significance. The Pearce Sellards Series no.2, Texas Memorial Museum, Austin, TX.

Young, Keith, 1967. Early Holocene earth movements, Travis county, Texas. Texas Journal of Science v.19, no.4, p.420-421.

16

Page 245: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

ACKNOWLEDGMENTS The 1992 South-Central Friends of the Pleistocene field trip would not be a

reality had it not been for the support and cooperation of a number of individuals, institutions, and businesses. Contributing authors and "communicators" are cited on the title page and throughout the text, but the editors wish to thank them collectively for the high quality of the papers and the timely submission of draft and revised text and figures. Other individuals whose assistance proved invaluable include the private landowners who opened their property for what must have appeared a bewildering blizzard of activity "just to look at some old dirt": Dr. D. L. Clark, Tuscon, AZ.; Mr. and Mrs. Johnnie Harrell, Smithville; Mrs. Jean Mcintyre, Falfurrias, TX, and her daughter Mrs. Sandra Stone, San Antonio; Mr. Joe Tiner, Smithville: and Mr. and Mrs. Tom Townsend, Bastrop. San Antonio Water Board allowed access to Applewhite Reservoir and actively supported investigations there, even providing a backhoe and operator for preparing trenches for the "Friends" field trip. Texas Parks and Wildlife Department allowed access to Bastrop State Park for preliminary research on the soils of high strath surfaces and provided "The Refectory" for our catered lunch on Friday; thanks to David Riskind for assisting to these ends. Other institutions deserving appreciation include: the Archeological Research Laboratory of Texas A&M University, College Station, for providing a van for the field trip and for supporting Alston Thoms's work to date at the Clark site; the Bureau of Economic Geology, Austin, for providing a van for I the field trip (special thanks to Tom Gustavson); the Department of Geological Sciences of The University of Texas at Austin for providing financial and logistical support and student ·volunteers"; the Geology Foundation of The University of Texas at Austin for providing financial support for backhoe excavations at the Rehmet locality; . I the Geology-Geography Department of The University of Nebraska, Omaha, for financial support and endless help in preparing the guidebook; the Soil Characterization Laboratory at Texas A&M University for providing soil analyses and supporting John Jacobs's research efforts at several of the field trip stops; the Soil Conservation Service, U.S. Department of Agriculture, for supporting research by Wayne Gabriel and Lynn Loomis, and for providing soil analyses through the National Soil Laboratory at Lincoln, NE; the Texas Archeological Research Laboratory of The University of Texas at Austin for serving as institutional sponsor and providing equipment for the alidade survey at thr Rehmet locality and the Ferris gravel pit; and the Vertebrate Paleontology Laboratory of The University of Texas at Austin for supporting research by Ernest Lundelius and for providing two vans for the field trip. The following individuals assited in many ways during the initial excavation at the Rehmet locality: John Arthur; David Brown; Dan and Martin Julien; Martin Lagoe; and Rick Toomey. Nan Olsen, Bastrop County Historic Commissioner and owner of the Bastrop Pit Barbecue Restaurant, served as coordinator for many of our efforts in the Bastrop area, for which we extend our gratitude. Finally, but in no way least, we wish to thank our corporate sponsors. Several companies have agreed to make contributions, but special thanks goes to Hicks and Company (Sandra Hicks, President), Austin, for much needed financial support in preparing the guidebook.

The editors would also like to thank their respective spouses and children, Sharon and new born Daniel Mandel and Kay, Abby, and Libby Caran, for patience and much needed support of all kinds. R. Mandel and C. Caran, eds.

Page 246: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

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Page 247: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

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Page 248: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

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Walsh Eolian Terrace Sands

SOtlth l~l

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Page 249: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

LATE PREHISTORIC APPLEWHTIE TERRACE

160 mr---------' ,-.,..: ~ LEciN~~~ALEOSOL I::~NL~crA~ 3,090±70 B.P .

.-r--~-r--r-r-,...MIDDLE~CHAIC.--. '. \ 4,135±70 B.P. MEDINA PALEOSOL I I L...--..I I I I I I \ 4,570±70 B.P.

" ! r-!EARLYARCHAIC':::r'~6,450±130 B.P. l-c---~~l--':; Y' LATE PALEOINDIAN /, i " '\ 6,930±65 B.P.

,-:;::::/~ _;~"" 9 780 ~ /4-'EiM CREEK PALEOSOL I I T··T-·T·-----l---l---l~-- __ l. 8, 780±210 B.P. _I 1 ." ±120 B;,P./~ I • I 9,200±130 B.P. I 19 ;8.7 0±120 B.P. "1' .i:. s:J'7~C::::~Y;:t:::r-r-...."-'-"" • I - I 'I'--"--"--r-'f I SOMERSET PALEOSOL MODERN FUXlD PlAlN \ PEREZ PALEOSOL . 9 800+140 B P. 10 780 140 B P. Stratified Gravels and Sands ... ~EREZPALEOSOL '~- • • . ,± . . • ... I I 1 I L-...J \.. "" .-1,410+70 B.P.

~~~~::~QJj.=Cf:;:::C:~======::713,480±360 B.P. 20,080±560 B.P. "? '. ~ARIVER L-...J SOIL? • /.13 960 150 B P. 13,640±210 B.P. "? \

SOILS ~;r- ,± . . . ? ,~/ 15,270±170 B.P.

155 m

!:'iO m

145 m

Stratified Gravels and Sands /

/

140 m :'J 500m 400m JOOm 200 100m 0

Richard Beene Site (41BX831)

Page 250: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

LEONA TERRACE: Hidden Valley Pedon.

Horiwn

Ap BklABk BklAB Bk1 Bk2 Bk3 2C 3Bkb

DejJth --cm--

0-25 25-55 25-55 55-90 90-133 133-190 190-205 205-255

eaC03 EQuiv. Org. Carbon ----------------------vvt. ~ ------------------------

12.8 38.6 59.0 44.3 50.9 49.6 58.6 50.5

1.52 0.73 0.67 0.34 0.35 0.39 0.10 0.25

WALSH TERRACE: Site 41BX540 Pedon.

Horiwn

Ap Ab 2Bts1bl 2Bts2bl 3BCb1 3CBbl 3Ck

Depth --cm--

0-27 27-63 63-112 112-164 164-203 203-250 250-280

----------------------vvt. ~ ------------------------0.0 0.38 0.0 0.31 0.0 0.40 0.0 0.27 0.0 0.13 0.0 0.10 8.1 0.02

Page 251: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Description of soil developed in Walsh Terrace fill at Site 41 BX540 .

Depth Color Struc- Tex- Consis- Bouo-Ifu~) Moist Dry lure ~ tence !Il!rL Svecial Features

Ap A

0-27 27-63

IOYR312 IOYR513 IOYR313

2Btslb 63-112 5YR313

2Bts2b 112-164 75YR4/4 (60%) 25YR4/6 (15%) IOYR7/4 (15%) 10YR312 (10%)

3BCb 164-203 7.5YR4/6

3CBb 203-250 75YR5/8 (60%) IOYR712 (30%) IOYR2I2 (10%)

3Ck 250-280 7.5YR4/6

M LS M LS

ImP-2mSBK SC

ImP-2mSBK SC

If+mSBK SCL

h. fr C,s

sl h, fr C,s

h, fr g,s

h, fr g,s

h, fr g,s

Connnon very fme roots; crossbedding. Common very fine roots; common krotovinas; few ironstone pebbles. Few fme roots; connnon ironstone pebbles; connnon pedotubuJes; about 50% of the pedotubuJes are filled with worm casts; many thick distinct continuous dark brown (7.5YR 3/3) clay fihns on vertical and horizontal ped faces. Discontinuous ironstone gravel lens at bottom of horizon; connnon thin continuous clay fihns on vertical ped faces;

Many very dark grayish brown (lOYR 312) worm casts.

If+mSBK FSL sl h, fr c,s Connnon ironstone pebbles.

M SL so, fr Few (1 %) light gray (lOYR712) soft carbonate bodies; matrix is non-caIcareous.

Abbreviations: Structure: l=weak, 2=moderate, 3=strong, f=fine, m=medinm, c=coarse, P=prismatic, SBK=subangular blocky, ABK=anguIar blocky, GR=granuJar, M=massive Texture: S=sand, Si=sil~ C=clay, L=loam,v=very, F=fine, Co=coarse, G=gravelly Consistence: fi=firm, fr=friable, h=hard, so=so~ v=very, sl=slightIy Boundaries: c=clear, g=gradua!, a=abrup~ s=smooth, w=wavy, i=irreguJar

Symbols: (+) and; (-) parting to

Page 252: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Description of the west wall of the Richard Beene Site (41 BX831).

Depth Co\ru: Slmc- Tex- Consis- Boun-Horizon (em) Moist Pry lure ture tence darv 3~jaLF~tur-'lll

Ap Bkl

Bk2

0-14 14-37

37-51

IOYR312 IOYR313 IOYR4/3 IOYR 513

Compacted CL Compacted CL

IOYR4/3 IOYRS/3 ImP-2f+mSBK CL

Modern surface soil welded into Leon Creek Paleosol Bk3(Abl) 51-87 IOYR4/3 IOYR413 ImP-2f+mSBK SiCL

Bk4 87-154 IOYR4/4 IOYRS/4 ImP-2f+mSBK SiCL

BCk 154-206 IOYRS/4 IOYR6/4 ImSBK L

CB 206-239 IOYR6/4 IOYR6/3 Ic+mSBK L

Medina Paleosol Akb2 239-289 IOYR514 IOYRS/4 1cP-2mSBK CL

ABkb2 289-317 IOYRS/4 IOYRS/4 ImP-2mSBK SiC

Bklb2 317-404 IOYR4/4 IOYRS/4 2mP-2f+mSBK SiCL

Bk2b2 404-560 IOYRS/4 IOYR6/4 ImP-2mSBK SiCL

Bk3b2 560-597 IOYRS/4 IOYRS/4 ImP-2mSBK SiCL

Bk4b2 597-693 IOYR514 IOYR5/4 ImP-2mSBK SiCL

h,fr

h,fr

h,fr

h,fr

h,fr

h,fr

h,fr

h,fr

h,fr

h,fr

h,fr

c,s Drastically disturbed by heavy earth-moving equipment. g,s Common pedotubules with very dark grayish brown (IOYR 312)

ftllings; fine flnffy threads of calcium carbonate cover 1-5 % of each ped surface.

g,s Many worm casts; few land snails; tme somewhat coalesced fluffy threads of calcium carbonate cover 10-20% of each ped surface.

g.s Carbonate morphology similar to overlying horizon but more coalesced fluffy threads.

c,s Carbonate morphology similar to overlying horizon but some encrusted and stained carbonates.

g,s Common worm casts; few (1-2 %) patchy threads and encrusted threads of calcium carbonate.

e,s Few pedotubnles; very few « I %) patchy threads of calcium carbonate.

g,s Lighter sandier zone (IOYR 6/4, dry) from 259-264 em; encrusted threads of calcium carbonate cover 5 % of each ped surface; very few fluffy carbonates (all coalesced).

g,s Encrusted threads of calcium carbonate cover 2-10% of each ped surface; no fluffy carbonates; few clay flows in pores.

g,s Encrusted threads of calcium carbonate cover 5-10% of each ped surface; very few fluffy carbonates; shiny pressure faces on some peds.

c,s Encrusted threads of calcium carbonate cover 5-10% of each ped surface; very few fluffy carbonates.

e,s Encrusted threads of calcium carbonate cover 5-10% of each ped surface; very few fluffy carbonates; cultural material in upper 5 em of the horizon.

c,s Common tubular carbonate forms that are about 2 em in diameter,and common carbonate plugs that are 5 mm in diameter. many tubules filled with shell fragments, charcoal, and brown (IOYR 513, dry) sediment.

Page 253: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

C2 693-720 lOYR6/4 lOYR6/4 M SiCL h,fr a.w

Elm Creek Paleosol Bklb3 720-768 IOYRS/6 lOYRS/6 If+mP-Im+cABK SiCL h,fr g,s

Bk2b3 768-820 lOYRS/6 IOYR5/6 ImP-Im+cABK SiCL h,fr g,s

CBb3 820-980 lOYRS/6 lOYR 7/4 lmABK CL h,fr g,s

C3 980-1,0201OYR6/4 IOYR7/4 M SiCL h,fr a.w

Perez Paleosol Bkb4 1,020-1,06875YR4/4 7.5YR6/4 IcP-2m+cABK SiCL vh,fi g,s

Bkssb4 1,068-1,136 7.5YR5/4 75YR6/4 2m+fABK SiCL vh,fi g,s

Bk'b4 1,136-1,169 75YR5/4 7.5YR6/4 2cABK SiCL vh, fi g,s

Distinct fine (1-2 mm thick) horizontal bedding; common 10YR 5/4 and lOYR 414 worm casts.

Few (2 %) hard encrusted carbonate threads I mm thick; few land snail shells. Few (0-1 %) bard encrusted carbonate threads I mm thick; a bed of7.5YR 5/6 silty clay loam with common (20%) carbonate Iithoclasts at a depth of 815-819 em. Faint fine (1-2 mm thick) horizontal bedding; common 10YR 5/4 worm casts. Faint horizontal bedding; common distinct strong brown (7.5YR 5/8) rhyzomottles; few (2-3%) light gray (IOYR 712) reduction zones around pores; few (I %) carbonare-tined tubules lhat are 5-8 mm wide and 10-20 em long.

Few round siliceous pebbles; few fine and medium pores; common medium distinct 7.5YR 6/4 mottles; 2-5% fine (1-2 mm) encrusted carbonate threads concentrated on ped faces; 5 % coarse carbonare-Iined pedotubules that are 5-8 mm wide and 10-20 em long; thin faint aureole of oxidized iron around the edges of pedotubules, bnt interiors of pedotubules are light gray (IOYR 712) iron depletion zones. Few round siliceous pebbles; few fine and medium pores; few (3%) brown (7.5YR 413) mottles; 2-5% fine (1-2 mm) encrusted carbonate threads concentrated on ped faces; 5% coarse carbonare-Iined pedotubules that are 5-8 mm wide and 10-20 em long; thin faint aureole of oxidized iron around the edges of pedotubules, hut interiors of pedotubules are light gray (IOYR 712) iron depletion zones; most faces are bounded by distinct slickensides that are inclined 20-30 degrees from the horizontal; moderate medium parallelpiepeds part to angular hlocky structure; some coarse and medium prismatic structure. Few round siliceous pebbles; common pores; few fine faint yellowish brown (7.5YR 5/6) mottles; 5% fme (1-2 mm) encrusted carbonate threads concentrated on ped faces; 5 % coarse carbonare-Iined pedotubules that are 5-8 mm wide and 10-20 em long; thin faint aureole of oxidized iron around the edges of pedotubules, but interiors of pedotubules are light gray (IOYR 712) iron depletion zones.

Page 254: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

BCkb4 1,169-1,227 75YR5/4 75YR6/4 Im+cABK CL vh, fi g,s Common rolWd siliceous pebbles and few rounded carbonate lithoclasts; common fme and medium pores; few fine faint yellowish brown (75YR 516) mottles; 5-10% fme (1-2 mm) encrusted carbonate threads concentrated on ped faces; 5-10% coarse carbonate-lined pedotubules that are 5-8 mm wide and 10-20 em long; thin faint aureole of oxidized iron arolWd the edges of pedotnbules, but interiors of pedotnbules are light gray (IOYR 712) iron depletion zones.

CBkb4 1,227-1,257 75YR5/4 75YR5/4 If+mABK CL vh, fi g.s Few rolWd siliceous pebbles; common fine and medium pores; few fine faint yellowish brown (75YR 5/6) mottles; 1 % coarse

carbonate-lined pedotubules that are 5-8 mm wide and 10- 20 em long; thin faint aureole of oxidized iron arolWd the edges of pedotnbules, but interiors of pedotnbules are light gray (IOYR 712) iron depletion zones.

Ck4 1,257-1,357 10YR 6/6 (50%) 10YR 7/4 (50%)

Soil 6 Bklb5 1,357-1,375 IOYRS/6 IOYR6/6

Bk2b5 1,357-1,459 IOYRS/6 IOYRS/6

Soil 7 Bkb6 1,459-1,505 IOYRS/6

Soil 8 Alb7 1,505-1,540 IOYR44

A2b7 1,540-1,575 10YRS/6

M FSL h,fr a,s Few lobular depletion zones as above; 1 % fine and very fine encrusted carbonates; 2 em thick lens of fine gravel 63 em below top of horizon.

lmABK SiCL h,fr g,s Few lobular depletion zones as above; 1 % fine encrusted carbonates; few fine faint yellowish brown (IOYR 5/8) mottles; many fine and medium pores.

ImSBK SiCL h,fr a,S Few lobular depletion zones as above; 1-2% fine encrusted carbonates; few fine faint yellowish brown (IOYR 5/8) mottles; common fine and medium pores.

ImSBK SiCL h,fi a.s Few distinct strong brown (7.5YR 4/6) mottles; common pale brown (JOYR 613) and brown (IOYR 513) pedotnbules;

IfSBK SiC

IfSBK SiC

h,fi g,s Few fine faint yellowish brown (J OYR 5/8) mottles; 1-2% depletion pedotnbules as above; < 1 % encrusted carbonates; few brown (JOYR 5/3) clay balls.

h,fi g,s Few fine faint yellowish brown (JOYR 5/8) mottles; 1-2% depletion pedotnbules as above; < 1 % encrusted carbonates; few pink (7.5YR 7/4) sand bodies; few brown (IOYR 513) clay balls.

Page 255: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

C7 1,575-1,600 IOYR7/4 (75%) IOYRS/8 (25%)

Somerset Paleosol Bkmb81,6QO..l,638 IOYR 812

M SiCL hJi a,i Few fine depletion pedotubules as above; few carbonates in pedotubules.

Laminar L vh c,s Eroded petrocalcic; dissolution cavities filled with dark sediment from above.

Abbreviations: Structure: l=weak, 2=moderate, 3=strong, £=fme, m=medium, c=coarse, !'=prismatic, SBK=subangnlar blocky, ABK=angn1ar blocky, GR=granular, M=massive Texture: S=sand, Si=silt, C=clay, L=loam, V=very, F=fine, Co=coarse, G=gravelly Consistence: fi=frrm, fr=friable. h=hard, so=soft, v=very. sl=slightly Boundaries: c=clear. g=gradual, a=abrupt, s=smooth. w=wavy. i=irregnlar

Symbols: (+) and; (-) parting to

Page 256: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Particle-size distributions: Richard Beene Site. Sand* Sill V. F. Sandi Clay free

HQrizon I!!m!!J VQ Q M E VF IQta! Q F IQ!l!! Q!ax I~ture Ei!l~ Sl!m! Sl!!ldlSi!! - -cm-- - - - - - - - - - - - - - - - - - - - - -WI. % - - - - - - - - - - - - - - - - - - - - - - - - - - - ------- WI. %-------

Ap ()()'14 0.1 0.2 1.5 14.5 15.2 30.7 13.3 27.5 40.8 28.5 CL 1.0 0.8 Bk1 14-37 0.0 0.2 1.4 13.8 13.4 28.4 11.5 31.9 43.4 28.2 CL 1.0 0.7 Bk2 37-44 0.1 0.1 1.0 11.7 10.6 23.1 11.0 34.1 45.1 31.8 CL 0.9 0.5 Bk2 44-51 0.0 0.1 1.1 9.4 9.7 19.9 9.8 36.4 46.1 34.0 CL 1.0 0.4

Modern surface soil welded into the Leon Creek Paleosol Bk3(Abl) 51-69 0.1 0.2 0.9 8.5 8.6 17.9 9.8 36.6 46.4 35.7 SiCL 1.0 0.4 Bk3(Abl) 69-87 0.1 0.2 1.0 8.7 7.6 17.2 7.9 37.9 45.8 37.0 SiCL 0.9 0.4 Bk4 87-120 0.0 0.1 1.2 9.5 7.2 17.6 7.3 38.5 45.8 36.6 SiCL 0.8 0.4 Bk4 120-154 0.0 0.1 1.7 15.3 7.9 24.5 6.4 35.2 41.6 33.9 CL 0.5 0.6 BCk 154-206 0.0 0.1 3.9 3.2 13.5 48.6 7.7 20.2 27.9 23.5 L 0.4 1.7 CB 206-223 0.1 0.1 1.1 19.7 18.3 38.7 12.3 24.7 37.0 24.3 L 0.9 1.0

Medina Paleosol Akb2 223-264 0.1 0.1 2.1 11.8 10.1 23.8 10.1 35.4 45.4 30.8 CL 0.9 0.5 Akb2 264-289 0.1 0.1 0.9 6.7 8.1 15.7 9.6 39.6 49.2 35.1 SiCL 1.2 0.3 ABkb2 289-317 0.0 0.1 0.4 3.3 4.5 8.1 9.9 41.1 51.1 40.8 SiC 1.4 0.2 Bk1b2 317-360 0.0 0.1 0.1 1.0 2.4 3.6 9.5 44.8 54.3 42.1 SiC 2.4 0.1 Bk1b2 360-404 0.1 0.0 0.1 0.8 3.2 4.1 14.2 42.0 56.2 39.7 SiCL 3.9 0.1 Bk2b2 404-456 0.0 0.0 0.1 0.6 3.2 3.8 10.2 47.5 57.7 38.5 SiCL 5.2 0.1 Bk2b2 456-508 0.1 0.1 0.3 1.9 5.1 7.4 13.9 43.1 57.0 35.6 SiCL 2.6 0.1 Bk2b2 508-560 0.1 0.1 0.1 0.7 3.8 4.5 9.9 46.1 56.0 39.5 SiCL 5.3 0.1 Bk3b2 560-597 0.0 0.1 0.1 2.6 4.9 7.5 10.2 43.1 53.3 39.2 SiCL 1.9 0.1 Bk4b2 597-693 0.1 0.3 0.7 4.8 6.8 12.4 8.7 41.2 49.9 37.7 SiCL 1.4 0.2 C2 693-706 0.0 0.1 0.1 1.6 7.5 9.1 14.5 41.1 55.6 35.3 SiCL 4.6 0.2 C2 706-720 0.1 0.0 0.0 3.0 9.7 12.5 13.6 39.6 53.2 34.3 SiCL 3.3 0.2

Elm Creek Paleosol Bk1b3 720-744 0.0 0.0 0.0 0.8 4.7 5.4 16.0 38.8 54.8 39.8 SiCL 5.7 0.1 Bk1b3 744-768 0.1 0.1 0.1 0.1 4.4 4.7 10.8 43.9 54.7 40.6 SiC 43.0 0.1 Bk2b3 768-794 0.1 0.0 0.1 1.1 6.0 7.1 12.6 40.6 53.1 39.8 SiCL 5.3 0.1 Bk2b3 794-820 0.0 0.1 0.2 1.3 4.9 6.4 10.8 43.4 54.2 39.4 SiCL 3.7 0.1 CBb3 820-980 0.1 0.0 0.1 5.8 20.3 25.5 13.1 30.0 43.1 31.4 CL 3.5 0.6 C3 980-1.000 0.0 0.1 0.2 2.8 13.3 15.9 16.7 35.0 51.8 32.3 SiCL 4.8 0.3 C3 1.000-1.020 0.0 0.0 0.1 3.1 12.3 15.0 15.8 34.0 49.8 35.2 SiCL 4.0 0.3

Page 257: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

S!IIl!l* Silt V. F. Sandi Clay free Horizon DeJl!b V~ ~ M F VF IQtal ~ F TQtal Clay I~3ture Eil!~ S!IIl!l S!IIlQLSilt

- -an-- - - - - - - - - - - - - - - - - - - - - -wI. % - - - - - - - - - - - - - - - - - - - - - - - - - - - ------- wI. %-------Perez Paleosol Bkb4 1,020-1,044 0.2 0.3 0.7 4.7 7.2 12.8 13.7 34.5 48.3 38.9 SiCL 1.5 0.3 Bkb4 1,044-1,068 0.2 0.5 1.1 6.0 7.0 14.4 11.2 38.5 49.7 35.9 SiCL 1.2 0.3 Bkssb4 1,068-1,102 0.2 0.4 0.9 7.0 7.0 15.1 13.0 32.6 45.6 39.3 SiCL 1.0 0.3 Bkssb4 1,102-1,136 0.3 0.6 1.3 7.6 7.5 16.9 12.8 30.4 43.2 39.9 SiCL 1.0 0.4 Bk1>4 1,136-1,169 0.3 0.6 1.6 9.6 7.8 19.5 10.2 31.4 41.6 38.9 SiCL 0.8 0.5 BCkb4 1,169-1,198 0.2 0.8 2.1 12.2 9.7 24.4 12.9 26.9 39.8 35.8 CL 0.8 0.6 BCkb4 1,198-1,227 0.6 0.8 3.5 17.0 13.1 34.2 10.5 24.5 35.0 30.8 CL 0.8 1.0 CBkb4 1,227-1,257 0.7 0.9 2.8 17.9 12.6 34.0 9.0 24.8 33.8 32.2 CL 0.7 1.0 C4 1,257-1,307 0.0 0.1 5.7 46.5 15.3 65.9 3.8 11.5 15.3 18.8 FSL 0.3 4.3 C4 1,307-1,357 0.2 0.7 9.5 49.5 12.0 70.1 4.5 10.2 14.6 15.3 FSL 0.2 4.8

Soil 6 Bklb5 1,357-1,375 0.0 0.2 1.8 33.8 16.5 51.7 5.3 17.6 23.0 25.3 SCL 0.5 2.3 Bk2b5 1,375-1,425 0.0 0.1 1.4 32.6 20.9 54.3 3.0 19.9 22.8 22.9 SCL 0.6 2.4 Bk2b5 1,425-1,459 0.0 0.0 0.4 14.5 16.7 31.2 11.3 27.9 39.1 29.7 CL 1.2 0.8

Soil 7 Bkb6 1,459-1.485 0.0 0.1 0.3 1.7 4.4 6.4 8.7 44.6 53.3 40.3 SiC 2.5 0.1 Bkb6 1,485-1,505 0.1 0.1 0.2 0.9 4.8 6.0 14.0 45.3 59.3 34.7 SiCL 5.2 0.1

Soil 8 Alb7 1,505-1,540 0.0 0.1 0.3 1.3 2.9 4.5 16.1 35.5 51.6 43.9 SiC 2.2 0.1 A2b7 1,540-1,575 0.0 0.1 5.5 1.2 2.8 9.4 5.6 45.2 50.8 39.8 SiCL 2.3 0.2 C7 1,575-1,600 0.1 0.0 1.2 2.1 3.6 6.6 10.8 49.1 59.9 33.5 SCL 1.7 0.1

Somerset Paleosol BkmbS 1,600-1,638 1.0 2.5 4.9 18.6 14.3 40.4 8.9 25.5 34.4 25.2 L 0.8 1.2 Bkl 1,638-1,676 0.2 1.1 3.2 21.7 16.0 41.4 8.7 27.3 35.9 22.7 L 0.7 1.2 Bk2 1,676-1,698 0.1 0.4 2.0 20.0 13.9 36.0 9.4 27.2 36.6 27.4 L 0.7 1.0 Bk2 1,698-1,720 0.0 0.2 1.2 14.4 13.8 29.2 15.7 25.7 41.5 29.3 CL 1.0 0.7 Bk3 1,720-1,745 0.0 0.1 0.1 1.0 2.4 3.6 9.5 44.8 54.3 42.1 SiC 2.4 0.1

*ParticIe-size limits (mm): Sand: VC = 2.0-1.0, C = 1.0-0.5, M = 0.5-0.25, F = 0.25-0.10, VF = 0.10-0.05 Silt: Total = 0.05-0.002, Fine = 0.02-0.002 Clay: Total = < 0.002, Fine = <0.0002

"I'exture classes: S=sand, Si=silt, C=clay, L=loarn, V=very, F=fme, Co=coarse, G=gravelIy, ex=extremely, v=very

Page 258: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 1. Radiocarbon ages determined on charcoal and soil humates from paleosols developed in the ApplewhiteTerrace fill.

Kf~eriar---------Radiocarbon------Deffa-------LaboraIory-------------

Dated A~ (B.P.) C·13 Number

Leon Cr. Paleosol Humate 2740±80 -19.0 TX-6569 Humate 281O±80 TX-6567 Humate 3050±70 -19.0 TX-6466 Charcoal 3090±70 Beta-36702 Humate 3210±90 -16.5 TX-6471 Humate 321O±90 -17.5 TX-6470 Charcoal 4135±70 -24.5 Beta-43330

Medina Paleosol Charcoal 4570±70 -26.3 Beta-38700 Humate 4670±120 -24.0 Beta-43332 Humate 4730±110 -18.8 TX-6568 Humate 4900±100 -18.4 TX-6571 Humate 5340±11O -18.9 TX-6464 Humate 5370±100 -18.6 TX-6468 Humate 5770±11O -17.4 TX-6463 Humate 641O±75 -23.7 Beta-43335 Humate 6450±135 -24.2 Beta-4333 Humate 7030±100 -23.5 Beta-44547 Humate 7900±100 -22.6 Beta-44548 Charcoal 801O±70 -25.5 Beta-44387 Humate 8080±130 -26.0 Beta-44386 Charcoal 8380±21O -23.0 Beta-44544

Elm Cr.Paleosol Humate 9170±11 0 -20.2 Beta-44541 Humate 9200±130 -22.4 Beta-44545 Humate 9670±120 -20.3 Beta-43542 Humate 9750±130 -21.0 Beta-43878 Humate 9780±120 -21.0 Beta-43877

Perez Paleosol Humate 9800±140 -20.1 Beta-44546 Humate 9870±120 -20.6 Beta-47565 Humate 10,040±120 -20.5 Beta-47566 Humate 10,130±120 -20.7 Beta-47567 Humate 10,780±140 -20.8 Beta-44543 Humate 11,070±220 -19.9 TX-6465 Humate 11,240±210 -20.9 TX-6570

Page 259: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Cont. Table 1

Kf~enar---------Radiocarbon-----lDeffa-------LiboraIory-------------

Dated Age (B,P,) C-l3 Number

Soil 6 Humate 13,480±360 -24.3

Soil 7 Humate 13,640±210 -26.6

Soil 8 Humate 13,960±150 -19.7 Humate 15,270±170 -20.9

Organic Silts 4 m below the Somerset Paleosol Humate 20,080±560 -22.6

Beta-47558

Beta-47559

Beta-47560 Beta-47561

Beta-47563

Bum wne about 4 m below the Somerset Paleosol. Alluviual deposit is inset against organic silts (see above).

Charcoal 32,850±530 Beta

Page 260: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

APPLEWHITE TERRACE: Site 4IBX831

Horizon

Ap Bk1 Bk2 Bk2

--cm--00-14 14-37 37-44 44-51

CaC03 Equiv. Organic Carbon ----------------------vvt. ~ ------------------------

49.6 1.26 52.5 1.07 52.8 0.90 53.2 0.79

Leon Creek Paleosol welded into modern surface soil Bk3 (Abl) 51-69 52.6 0.84 Bk3 (Abl) 69-87 53.7 0.60 Bk4 87-120 51.7 0.52 Bk4 120-154 55.5 0.12 BC 154-206 60.4 0.29 CB 206-223 55.3 0.06

Medina Paleosol Akb2 Akb2 ABkb2 Bk1b2 Bk1b2 Bk2b2 Bk2b2 Bk2b2 Bk3b2 Bk4b2 C2 C2

223-264 264-289 289-317 317-360 360-404 404-456 456-508 508-560 560-597 597-693 693-706 706-720

Elm Creek Paleosol Bklb3 720-744 Bklb3 744-768 Bk2b3 768-794 Bk2b3 794-820 CBb3 820-980 C3 980-1,000 C3 1,000-1,020

Perez Paleosol Bkb4 Bkb4 Bkssb4 Bkssb4 Bk'b4 BCkb4 BCkb4 CBkb4 C4 C4

1,020-1,044 1,044-1,068 1,068-1,102 1,102-1,136 1,136-1,169 1,169-1,198 1,198-1,227 1,227-1,257 1,257-1,307 1,307-1,357

52.4 50.8 48.9 46.7 48.7 48.6 48.0 49.2 45.2 47.2 47.9 47.8

41.0 43.5 43.3 45.7 47.6 48.5 47.4

42.9 40.6 38.2 37.9 38.0 41.1 42.1 44.9 20.9 21.8

0.33 0.27 0.24 0.29 0.20 0.23 0.17 0.15 0.45 0.46 0.31 0.44

0.54 0.46 0.24 0.23 0.53 0.06 0.11

0.29 0.27 0.29 0.16 0.12 0.27 0.13 0.13 0.14 0.05

Page 261: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Horiwn Depth CaC03 Equiv. Organic Carbon ~m- -------------------vvt. ~ ------------------

Soil 6 Bk1b5 1,357-1,375 22.3 0.73 Bk2b5 1,375-1,425 38.3 0.11 Bk2b5 1,425-1,459 40.5 0.23

Soil 7 Bkb6 1,459-1,485 44.0 0.59 Bkb6 1,485-1,505 53.6 0.50

Soil 8 A1b7 1,505-1,540 40.7 0.93 A1b7 1,540-1,575 45.8 0.46 C7 1,575-1,600 65.3 0.10

Somerset Paleosol Bkmb8 1,600-1,638 69.3 0.02 Bk1b8 1,638-1,676 61.8 0.33 Bk2b8 1,676-1,698 55.9 0.34 Bk2b8 1,698-1,720 55.6 0.30 Bk3b8 1,720-1,745 55.3 0.34

Page 262: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Walsh

South

V~rtical

SClll~

Iml

t:,

Eolian Sands

1

Bedrock

Leona Applewhite Terrace

1

~'?

,

"

", "

Bedrock

Miller Terrace

1

~" ? -' .... ? ? .. ". ...

Applewhite Terrace

1

Covered

Bedrock

North

Page 263: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

LATE PREHISTORIC APPLEWHITE TERRACE

160 mf---------c ;:~ '-T', :' ~ciN~~~A~~~~ [~fT~A~C!Ef~~,090±70 B.P.

MIDDLE~CHAIC ,-----. '. \ 4,135±70 B.P. I ~E~IN~ P~LE~S~r:-\ [ L:.-....o I I I FT'\ 4,570±70 B.P.

, r- EARLY ARCHAIC ':::r'o----;,- 6,450±130 B.P. ~, I 'X LATEPALEOINDIAN / I , : '. \\ 6,930±65 B.P.

'-:;::":/:::::=, _'~"" 9 780 1 0 ~~ELMCREEKPAlEOSOL I I I I---r-T---ml---l---l~-- _:. 8, 780±210 B.P. _I 1 1°" ± 2 B.P. ./ I ° r 9,200±130 B.P. 19;870±120 B.P / , , .

0\1- I "l'--o--_--r/f r SOMERSEfPALEOSOL MODERN FLOOD PlAIN PEREZ PALEOSOL 9 800+140 B P.

10 780 140 B P. Strati fled Gravels and Sands .. ~EREZ PALEOSOL '~- • • . ,±.. • ,1111 ........... \.. "" 0-~,410±?~B.P.

~~~~::~q,;;n;:;:::;i~ ____ :::=====::713,480±360 B.P. 20,080±560 B.P. "? ,\~INARIVER ~ SOIL 7 • °/-13 960 150 B P. 13,640±210 B.P. \? ...

SOIL8 ,,7'" ,±. . . . '? ~., 15,270±170 B.P. .-,// StratIfied Gravels and Sands

!55 m

ISO m

145 m

140 m ":J 500m 400m 300m 200 100m 0

Richard Beene Site (41BX831)

Page 264: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

LEONA TERRACE: Hidden Valley Pedon.

Horizon

Ap BklABk BkiAB Bkl Bk2 Bk3 2C 3Bkb

De.pth --cm--

0-25 25-55 25-55 55-90 90-133 133-190 190-205 205-255

CaC03 Equiv. Org. Carbon ----------------------vvt. ~ ------------------------

12.8 38.6 59.0 44.3 50.9 49.6 58.6 50.5

1.52 0.73 0.67 0.34 0.35 0.39 0.10 0.25

WALSH TERRACE: Site41BX540 Pedon.

Horizon

Ap Ab 2Btslbl 2Bts2bl 3BCbl 3CBbi 3Ck

Depth --cm--

0-27 27-63 63-112 112-164 164-203 203-250 250-280

CaC03 Equiv. Org. Carbon ----------------------vvt. ~ ------------------------

0.0 0.38 0.0 0.31 0.0 0.40 0.0 0.27 0.0 0.13 0.0 0.10 8.1 0.02

Page 265: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Description of soil developed in Walsh Terrace fill at Site 41 BX540 .

Depth Color Strue- Tex- Consis- BoWl-Hmiwn (em) Moist Pry ture lUre tence dary S~ialEeatures

Ap 0-27 IOYR312 IOYRS/3 M LS h,fr e,s Common very tme roots; crossbedding. A 27-63 IOYR313 M LS sl h, fr e,s Common very fine roots; common krotovinas; few ironstone

pebbles. 2Btslb 63-112 5YR313 ImP-2mSBK SC h, fr g,s Few tme roots; common ironstone pebbles; common

pedotnbuJes; about 50% of the pedotnbuJes are tilled with worm casts; many thick distinct continuons dark brown (7.5YR 3/3) clay films on vertical aud horizontal ped faces.

2Bts2b 112-164 7.5YR4/4 (60%) ImP-2mSBK SC h, fr g,s Discontinuons ironstone gravel lens at bottom of horizon; 2.5YR4/6 (15%) common thin continuous clay fi1ms on vertical ped faces; IOYR7/4 (15%) IOYR312 (10%)

3BCb 164-203 7.5YR4/6 If+mSBK SCL h, fr g,s Mauy very dark grayish brown (IOYR 312) worm casts.

3CBb 203-250 7.5YRS/8 (60%) if+mSBK FSL sl h, fr e,s Common ironstone pebbles. IOYR712 (30%) IOYR2I2 (10%)

3Ck 250-280 7.5YR4I6 M SL 8O,fr Few (I %) light gray (IOYR712) soft carbonate bodies; matrix is non-<Oalcareous.

Abbreviations: Structure: l=weak, 2=moderate, 3=strong, f=fme. m=medium, c=coarse, P=prismatie, SBK=subaugular blocky, ABK=augular blocky, GR=granuJar, M=massive Texture: S=saud, Si=silt, C=clay, L=loam,V=very, F=fme, Co=coarse, G=graveUy Consistence: fi=firm, fr=friable. h=hard, so=soft, v=very, sl=slightly Boundaries: c=clear, g=gradual, .=abrupt, s=smooth. w=wavy. i=irreguJar

Symbols: (+) aud; (-) parting to

Page 266: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Description of the west wall of the Richard Beene Site (4IBX831).

Depth Color Shuc- Tex- Consis- BOIID-Horizon (cm) Moist _ Drv _______ twe ___ twe __ t~m;e __ da!:Y __ Soo;jaLE~tt!r~

Ap ()"14 IOYR312 IOYR3/3 Compacted CL c.s Drastically disturbed by heavy earth-moving equipment. Bkl 14-37 IOYR4/3 IOYR 5/3 Compacted CL g,s Common pedotubules with very dark grayish brown (IOYR 312)

fillings; fine fluffy threads of calcium carbonate cover 1-5 % of each ped surface.

Bk2 37-51 IOYR4/3 IOYR5/3 ImP-2f+mSBK CL h,fr g,s Many worm casts; few land snails; tme somewhat coalesced fluffy threads of calcium carbonate cover I ().. 20% of each ped surtace.

Modern surface soil welded into Leon Creek Paleosol Bk3(Abl) 51-87 IOYR4/3 IOYR413 ImP-2f+mSBK SiCL h,fr g,s Carbonate morphology similar to overlying horizon but more

coalesced fluffy threads. Bk4 87-154 10YR4/4 IOYR5/4 lmP-2f+mSBK SiCL h,fr e.s Carbonate morphology similar to overlying horizon but some

enem<ted and stained carbonates. BCk 154-206 IOYRS/4 10YR6/4 ImSBK L h,fr g,s Common worm casts; few (I -2 %) patchy threads and encmsted

threads of calcium carbonate. CB 206-239 IOYR6/4 IOYR6/3 Ic+mSBK L h,fr c,s Few pedotubules; very few « 1 %) patchy threads of calcium

carbonate. Medina Paleosol Akb2 239-289 IOYR5/4 IOYRS/4 leP-2mSBK CL h,fr g,s Lighter sandier zone (IOYR 6/4, dry) from 259-264 em;

encmsted threads of calcium carbonate cover 5 % of each ped surface; very few flnffy carbonates (all coalesced).

ABkb2 289-317 10YRS/4 IOYR514 ImP-2mSBK SiC h,fr g,s Encmsted threads of calcium carbonate cover 2-10% of each ped surface; no fluffy carbonates; few clay flows in pores.

Bklb2 317-404 IOYR4/4 IOYRS/4 2mP-2f+mSBK SiCL h,fr g,s Encmsted threads of calcium carbonate cover 5-10% of each ped surface; very few flnffy carbonates; shiny pressure faces on some peds.

Bk2b2 404-560 IOYRS/4 IOYR6/4 ImP-2mSBK SiCL h,fr e,s Encmsted threads of calcium carbonate cover 5-10% of each ped surface; very few fluffy carbonates.

Bk3b2 560-597 IOYRS/4 IOYRS/4 ImP-2mSBK SiCL h,fr e,s Encrusted threads of calcium carbonate cover 5-10% of each ped surface; very few fluffy carbonates; cnltural material in upper 5 em of the horizon.

Bk4b2 597-693 IOYR5/4 IOYR5/4 ImP-2mSBK SiCL h,fr c,s Common tubular carbonate forms that are about 2 em in diameter,and common carbonate plugs that are 5 mm in diameter; many tubules filled with shell fragments, charcoal, and brown (IOYR 5/3, dry) sediment.

Page 267: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

C2 693-720 IOYR6/4 IOYR6/4 M SiCL h,fr a,w

Elm Creek Paleosol Bklb3 720-768 IOYRSI6 IOYR516 If+mP-Im+cABK SiCL h,fr g,s

Bk2b3 768-820 IOYRSI6 IOYR516 ImP-lm+cABK SiCL h,fr g,s

CBb3 820-980 IOYRS/6 IOYR 7/4 lmABK CL h,fr g,s

C3 980-1,0201OYR6/4 IOYR7/4 M SiCL h,fr a,w

Perez Paleosol Bkb4 1,020-1,068 7.5YR4/4 7.5YR6/4 IcP-2m+cABK SiCL vh,fi g,s

Bkssb4 1,068-1,136 7.5YRS/4 7.5YR6/4 2m+fABK SiCL vh,fi g,s

Bk'b4 1,136-1,169 7.5YR5/4 7.5YR6/4 2cABK SiCL vb, fi g,s

Distinct fme (1-2 mm thick) horizontal bedding; common 10YR 514 and 10YR 414 worm casts.

Few (2 %) hard encrusted carbonate threada 1 mm thick; few land snail shells. Few (0-1 %) hard encrusted carbonate threada 1 mm thick; a bed of 7.5YR 516 silty clay loam wi!h common (20%) carbonate li!hoclasts at a dep!h of 815-819 em. Faint fine (1-2 mm thick) horizontal bedding; common 10YR 514 worm casts. Faint horizontal bedding; common distinct strong brown (7.5YR 5/8) rhyzomottles; few (2-3%) light gray (IOYR 712) reduction zones around pores; few (I %) carbonate-lined tubules !hat are 5-8 mm wide and 10-20 em long.

Few round siliceous pebbles; few fine and medium pores; common medium distinct 7.5YR 6/4 mottles; 2-5% fine (1-2 mm) encrusted carbonate threada concentrated on ped faces; 5 % coarse carbonate-lined pedotubules !hat are 5-8 mm wide and 10-20 em long; 1hin faint aureole of oxidized iron around !he edges of pedotubules, but interiors of pedotubules are light gray (IOYR 712) iron depletion zones. Few round siliceous pebbles; few fine and medium pores; few (3%) brown (7.5YR 413) mottles; 2-5% fine (1-2 mm) encrusted carbonate threada concentrated on ped faces; 5 % coarse carbonate-lined pedotubules that are 5-8 mm wide and 10-20 em long; 1hin faint aureole of oxidized iron around !he edges of pedotubules, but interiors of pedotubules are light gray (10YR 712) iron depletion zones; most faces are bounded by distinct slickensides !hat are inclined 20-30 degrees from !he horizontal; moderate medium paraIIelpiepeds part to angular blocky structure; some coarse and medium prismatic structure. Few round siliceous pebbles; common pores; few fine faint yellowish brown (7.5YR 516) mottles; 5% fme (1-2 mm) encrusted carbonate threada concentrated on ped faces; 5 % coarse carbonate-lined pedotubules!hat are 5-8 mm wide and 10-20 em long; 1hin faint aureole of oxidized iron around !he edges of pedotubules, but interiors of pedotubules are light gray (IOYR 712) iron depletion zones.

Page 268: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

BCkb4 1,169-1,227 7.5YR5/4 7.5YR6/4 Im+cABK CL vh, fi g,s Common roood siliceons pebbles and few ronnded carbonate lithoclasts; COmmon fme and medium pores; few fine faint yellowish brown (7.5YR 516) mottles; 5-10% fme (1-2 mm) encrusted carbonate threads concentrated on ped faces; 5-10% coarse carbonate-lined pedotubules that are 5-8 mm wide and 10-20 em long; thin faint aureole of oxidized iron aroood the edges of pedotobules, bnt interiors of pedotobules are light gray (10YR 712) iron depletion zones.

CBkb4 1,227-1,257 7.5YR5/4 7.5YR5/4 If+mABK CL vh, fi g,s Few roood siliceons pebbles; common fine and medium pores; few fme faint yellowish brown (7.5YR 516) mottles; 1 % coan;e

carbonate-lined pedotubules that are 5-8 mm wide and 10- 20 cm long; thin faint aureole of oxidized iron aroood the edges of pedotobules, but interiors of pedotobnles are light gray (10YR 712) iron depletion zones.

Ck4 1,257-1,357 10YR 6/6 (50%) 10YR 7/4 (50%)

Soil 6 Bklb5 1,357-1,375 IOYR5/6 IOYR6/6

Bk2b5 1,357-1,459 IOYR5/6 IOYR5/6

Soil 7 Bkb6 1,459-1,505 10YR5/6

Soil 8 Alb7 1,505-1,540 IOYR44

A2b7 1,540-1,575 10YR5/6

M FSL h,fr a,s Few tobular depletion zones as above; 1 % fine and very fine encrusted carbonates; 2 em thick lens of fine gravel 63 em below top of horizon.

lmABK SiCL h,fr g,s Few tobular depletion zones as above; 1 % fine encrusted carbonates; few fine faint yellowish brown (1 OYR 5/8) mottles; many fine and medium pores.

ImSBK SiCL h,fr a.s Few tobular depletion zones as above; 1-2% fine encrusted carbonates; few fine faint yellowish brown (I OYR 5/8) mottles; common fine and medium pores.

ImSBK SiCL h,fi a,s Few distinct slrong brown (7.5YR 4/6) mottles; common pale brown (10YR 613) and brown (lOYR 513) pedotobules;

IfSBK SiC

IfSBK SiC

h,fi g,s Few fine faint yellowish brown (lOYR 5/8) mottles; 1-2% depletion pedotobules as above; < 1 % encrusted carbonates; few brown (IOYR 513) clay balls.

h,fi g,s Few fine faint yellowish brown (lOYR 5/8) mottles; 1-2% depletion pedotobules as above; < 1 % encrusted carbonates; few pink (7.5YR 7/4) sand bodies; few brown (IOYR 513) clay balls.

Page 269: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

C7 1,575-1,600 IOYR7/4 (75%) IOYRS/8 (25%)

Somerset Paleosol Bkmb81,600-I,638 IOYR 8fl.

M SiCL bJi a,i Few fine depletion pedotubules as above; few carbonates in pedotubules.

Laminar L vb c,s Eroded petrocalcic; dissolution cavities filled with dark sediment from above.

Abbreviations: Structure: l=weak, 2=moderate, 3=strong, f=fme, m=mediwn, =coarse, !'=prismatic, SBK=subangular blocky, ABK=anguJar blocky, GR=granular, M=massive Texture: S=sand, Si=sill, C=clay, L=loam,V=very, F=fine, Co=coarse, G=gravelly Consistence: fi=f"mn. fr=friable, h=hard, so=soft, v=very, sl=slightly Boundaries: =clear, g=gradual, a=abrupt, s=smooth, w=wavy, i=irreguJar

Symbols: (+) and; (-) parting to

Page 270: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Particle-size distributions: Richard Beene Site. San\!* Silt V. F. Sandi Clay free

Horizon Il~1!!b vC C M E VF Total C F Total Clav I~ture Fin~ S;m\! S;mdlSilt - -cm-- - - - - - - - - - - - - - - - - - - - - -WI. % - - - - - - - - - - - - - - - - - - - - - - - - - - - ------- WI. %-------

Ap ()()"14 0.1 0.2 1.5 14.5 15.2 30.7 13.3 27.5 40.8 28.5 CL 1.0 0.8 Bkl 14-37 0.0 0.2 1.4 13.8 13.4 28.4 11.5 31.9 43.4 28.2 CL 1.0 0.7 Bk2 37-44 0.1 0.1 1.0 11.7 10.6 23.1 11.0 34.1 45.1 31.8 CL 0.9 0.5 Bk2 44-51 0.0 0.1 1.1 9.4 9.7 19.9 9.8 36.4 46.1 34.0 CL 1.0 0.4

Modern surface soil welded into the Leon Creek Paleosol Bk3(Abl) 51-69 0.1 0.2 0.9 8.5 8.6 17.9 9.8 36.6 46.4 35.7 SiCL 1.0 0.4 Bk3(Abl) 69-87 0.1 0.2 1.0 8.7 7.6 17.2 7.9 37.9 45.8 37.0 SiCL 0.9 0.4 Bk4 87-120 0.0 0.1 1.2 9.5 7.2 17.6 7.3 38.5 45.8 36.6 SiCL 0.8 0.4 Bk4 120-154 0.0 0.1 1.7 15.3 7.9 24.5 6.4 35.2 41.6 33.9 CL 0.5 0.6 BCk 154-206 0.0 0.1 3.9 3.2 13.5 48.6 7.7 20.2 27.9 23.5 L 0.4 1.7 CB 206-223 0.1 0.1 1.1 19.7 18.3 38.7 12.3 24.7 37.0 24.3 L 0.9 1.0

Medina Paleosol Akb2 223-264 0.1 0.1 2.1 11.8 10.1 23.8 10.1 35.4 45.4 30.8 CL 0.9 0.5 Akb2 264-289 0.1 0.1 0.9 6.7 8.1 15.7 9.6 39.6 49.2 35.1 SiCL 1.2 0.3 ABkb2 289-317 0.0 0.1 0.4 3.3 4.5 8.1 9.9 41.1 51.1 40.8 SiC 1.4 0.2 Bklb2 317-360 0.0 0.1 0.1 1.0 2.4 3.6 9.5 44.8 54.3 42.1 SiC 2.4 0.1 Bklb2 360-404 0.1 0.0 0.1 0.8 3.2 4.1 14.2 42.0 56.2 39.7 SiCL 3.9 0.1 Bk2b2 404-456 0.0 0.0 0.1 0.6 3.2 3.8 10.2 47.5 57.7 38.5 SiCL 5.2 0.1 Bk2b2 456-508 0.1 0.1 0.3 1.9 5.1 7.4 13.9 43.1 57.0 35.6 SiCL 2.6 0.1 Bk2b2 508-560 0.1 0.1 0.1 0.7 3.8 4.5 9.9 46.1 56.0 39.5 SiCL 5.3 0.1 Bk3b2 560-597 0.0 0.1 0.1 2.6 4.9 7.5 10.2 43.1 53.3 39.2 SiCL 1.9 0.1 Bk4b2 597-693 0.1 0.3 0.7 4.8 6.8 12.4 8.7 41.2 49.9 37.7 SiCL 1.4 0.2 C2 693-706 0.0 0.1 0.1 1.6 7.5 9.1 14.5 41.1 55.6 35.3 SiCL 4.6 0.2 C2 706-720 0.1 0.0 0.0 3.0 9.7 12.5 13.6 39.6 53.2 34.3 SiCL 3.3 0.2

Elm Creek Paleosol Bklb3 720-744 0.0 0.0 0.0 0.8 4.7 5.4 16.0 38.8 54.8 39.8 SiCL 5.7 0.1 Bklb3 744-768 0.1 0.1 0.1 0.1 4.4 4.7 10.8 43.9 54.7 40.6 SiC 43.0 0.1 Bk2b3 768-794 0.1 0.0 0.1 1.1 6.0 7.1 12.6 40.6 53.1 39.8 SiCL 5.3 0.1 Bk2b3 794-820 0.0 0.1 0.2 1.3 4.9 6.4 10.8 43.4 54.2 39.4 SiCL 3.7 0.1 CBb3 820-980 0.1 0.0 0.1 5.8 20.3 25.5 13.1 30.0 43.1 31.4 CL 3.5 0.6 C3 980-1,000 0.0 0.1 0.2 2.8 13.3 15.9 16.7 35.0 51.8 32.3 SiCL 4.8 0.3 C3 1,000-1,020 0.0 0.0 0.1 3.1 12.3 15.0 15.8 34.0 49.8 35.2 SiCL 4.0 0.3

Page 271: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Sood'" Silt V. F. Sand! Clay free HQrizon Deoth VC C M F vE Iotal C E Total Cia): r~xture Ei!!!l Sand SoodlSil!

- -CIll- - - - - - - - - - - - - - - - - - - - - - -wI. % - - - - - - - - - - - - - - - - - - - - - - - - - - - ------- wI. %-------Perez Paleosol Bkb4 1.020-1.044 0.2 0.3 0.7 4.7 7.2 12.8 13.7 34.5 48.3 38.9 SiCL 1.5 0.3 Bkb4 1,044-1,068 0.2 0.5 1.1 6.0 7.0 14.4 11.2 38.5 49.7 35.9 SiCL 1.2 0.3 Bkssb4 1,068-1,102 0.2 0.4 0.9 7.0 7.0 15.1 13.0 32.6 45.6 39.3 SiCL 1.0 0.3 Bkssb4 1,102-1,136 0.3 0.6 1.3 7.6 7.5 16.9 12.8 30.4 43.2 39.9 SiCL 1.0 0.4 Bk'b4 1,136-1,169 0.3 0.6 1.6 9.6 7.8 19.5 10.2 31.4 41.6 38.9 SiCL 0.8 0.5 BCkb4 1,169-1,198 0.2 0.8 2.1 12.2 9.7 24.4 12.9 26.9 39.8 35.8 CL 0.8 0.6 BCkb4 1,198-1,227 0.6 0.8 3.5 17.0 13.1 34.2 10.5 24.5 35.0 30.8 CL 0.8 1.0 CBkb4 1,227-1,257 0.7 0.9 2.8 17.9 12.6 34.0 9.0 24.8 33.8 32.2 CL 0.7 1.0 C4 1,257-1,307 0.0 0.1 5.7 46.5 15.3 65.9 3.8 11.5 15.3 18.8 FSL 0.3 4.3 C4 1,307-1,357 0.2 0.7 9.5 49.5 12.0 70.1 4.5 10.2 14.6 15.3 FSL 0.2 4.8

Soil 6 Bklb5 1,357-1,375 0.0 0.2 1.8 33.8 16.5 51.7 5.3 17.6 23.0 25.3 SCL 0.5 2.3 Bk2b5 1,375-1,425 0.0 0.1 1.4 32.6 20.9 54.3 3.0 19.9 22.8 22.9 SCL 0.6 2.4 Bk2b5 1.425-1,459 0.0 0.0 0.4 14.5 16.7 31.2 11.3 27.9 39.1 29.7 CL 1.2 0.8

Soil 7 Bkb6 1,459-1,485 0.0 0.1 0.3 1.7 4.4 6.4 8.7 44.6 53.3 40.3 SiC 2.5 0.1 Bkb6 1,485-1,505 0.1 0.1 0.2 0.9 4.8 6.0 14.0 45.3 59.3 34.7 SiCL 5.2 0.1

Soil 8 Alb7 1,505-1,540 0.0 0.1 0.3 1.3 2.9 4.5 16.1 35.5 51.6 43.9 SiC 2.2 0.1 A2b7 1,540-1,575 0.0 0.1 5.5 1.2 2.8 9.4 5.6 45.2 50.8 39.8 SiCL 2.3 0.2 C7 1,575-1,600 0.1 0.0 1.2 2.1 3.6 6.6 10.8 49.1 59.9 33.5 SCL 1.7 0.1

Somerset Paleosol BkmbS 1,600-1,638 1.0 2.5 4.9 18.6 14.3 40.4 8.9 25.5 34.4 25.2 L 0.8 1.2 Bkl 1,638-1,676 0.2 1.1 3.2 21.7 16.0 41.4 8.7 27.3 35.9 22.7 L 0.7 1.2 Bk2 1,676-1,698 0.1 0.4 2.0 20.0 13.9 36.0 9.4 27.2 36.6 27.4 L 0.7 1.0 Bk2 1.698-1,720 0.0 0.2 1.2 14.4 13.8 29.2 15.7 25.7 41.5 29.3 CL 1.0 0.7 Bk3 1.720-1,745 0.0 0.1 0.1 1.0 2.4 3.6 9.5 44.8 54.3 42.1 SiC 2.4 0.1

"'Particle-size limits (rom): Sand: VC = 2.0-1.0. C = 1.0-0.5, M = 0.5-0.25, F = 0.25-0.10, VF = 0.10-0.05 Silt: Total = 0.05-0.002, Fine = 0.02-0.002 Clay: Total = < 0.002, Fine = <0.0002

"fexture classes: S=sand, Si=silt. C=clay, L=loam,V=very, F=f'me, Co=coarse, G=graveUy. ex=extremely. v=very

Page 272: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Table 1. Radiocarbon ages detennined on charcoal and soil humates from paleosols developed in the ApplewhiteTerrace fill.

Kfateriaf---------Raillocarbon------DeHa-------Caboratory-------------Dated Age m.p.) C-13 Number

Leon Cr. Paleosol Humate 2740±80 -19.0 TX-6569 Humate 281O±80 TX-6567 Humate 3050±70 -19.0 TX-6466 Charcoal 3090±70 Beta-36702 Humate 321O±90 -16.5 TX-6471 Humate 3210±90 -17.5 TX-6470 Charcoal 4135±70 -24.5 Beta-43330

Medina Paleosol Charcoal 4570±70 -26.3 Beta-38700 Humate 4670±120 -24.0 Beta-43332 Humate 4730±110 -18.8 TX-6568 Humate 4900±100 -18.4 TX-6571 Humate 5340±110 -18.9 TX-6464 Humate 5370±100 -18.6 TX-6468 Humate 5770±11 0 -17.4 TX-6463 Humate 641O±75 -23.7 Beta-43335 Humate 6450±135 -24.2 Beta-4333 Humate 7030±100 -23.5 Beta-44547 Humate 7900±100 -22.6 Beta-44548 Charcoal 801O±70 -25.5 Beta-44387 Humate 8080±130 -26.0 Beta-44386 Charcoal 8380±210 -23.0 Beta-44544

Elm Cr.Paleosol Humate 9170±110 -20.2 Beta-44541 Humate 9200±130 -22.4 Beta-44545 Humate 9670±120 -20.3 Beta-43542 Humate 9750±130 -21.0 Beta-43878 Humate 9780±120 -21.0 Beta-43877

Perez Paleosol Humate 9800±140 -20.1 Beta-44546 Humate 9870±120 -20.6 Beta-47565 Humate 10,040±120 -20.5 Beta-47566 Humate IO,130±120 -20.7 Beta-47567 Humate IO,780±140 -20.8 Beta-44543 Humate ll,070±220 -19.9 TX-6465 Humate ll,240±210 -20.9 TX-6570

Page 273: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Cont. Table I

~a~riaf---------Radiocar6on------Deffa-------Caboratori------------Dated Age (B,P,) C-B Number

Soil 6 Humate 13,480±360 -24,3

Soil 7 Humate 13,640±2JO -26,6

Soil 8 Humate 13,960±150 -19,7 Humate 15,270±170 ·20,9

Organic Silts 4 m below the Somerset Paleosol Humate 20,080±560 -22,6

Beta-47558

Beta-47559

Beta-47560 Beta-47561

Beta-47563

Burn zone about 4 m below the Somerset Paleosol. Alluviual deposit is inset against organic silts (see above),

Charcoal 32,850±530 Beta

Page 274: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

APPLEWHITE TERRACE: Site 41BX831

Horizon

Ap Bkl Bk2 Bk2

Depth --cm--

00-14 14-37 37-44 44-51

CaC03 EQuiv. Organic Carbon ----------------------vvt. 91a ------------------------

49.6 1.26 52.5 1.07 52.8 0.90 53.2 0.79

Leon Creek Paleosol welded into modern surface soil Bk3 (Abl) 51-69 52.6 0.84 Bk3 (Abl) 69-87 53.7 0.60 Bk4 87-120 51. 7 0.52 Bk4 120-154 55.5 0.12 BC 154-206 60.4 0.29 CB 206-223 55.3 0.06

Medina Paleosol Akb2 223-264 Akb2 264-289 ABkb2 289-317 Bklb2 317-360 Bklb2 360-404 Bk2b2 404-456 Bk2b2 456-508 Bk2b2 508-560 Bk3b2 560-597 Bk4b2 597-693 C2 693-706 C2 706-720

Elm Creek Paleosol Bklb3 720-744 Bklb3 744-768 Bk2b3 768-794 Bk2b3 794-820 CBb3 820-980 C3 980-1,000 C3 1,000-1,020

Perez Paleosol Bkb4 1,020-1,044 Bkb4 1,044-1,068 Bkssb4 1,068-1,102 Bkssb4 1,102-1,136 Bk'b4 1,136-1,169 BCkb4 1,169-1,198 BCkb4 1,198-1,227 CBkb4 1,227-1,257 C4 1,257-1,307 C4 1,307-1,357

52.4 50.8 48.9 46.7 48.7 48.6 48.0 49.2 45.2 47.2 47.9 47.8

41.0 43.5 43.3 45.7 47.6 48.5 47.4

42.9 40.6 38.2 37.9 38.0 41.1 42.1 44.9 20.9 21.8

0.33 0.27 0.24 0.29 0.20 0.23 0.l7 0.15 0.45 0.46 0.31 0.44

0.54 0.46 0.24 0.23 0.53 0.06 0.11

0.29 0.27 0.29 0.16 0.12 0.27 0.13 0.13 0.14 0.05

Page 275: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Horizon Dtmth CaC03 EQuiv. Organic Carbon -cm- --------------------vvt. ~ ------------------

Soil 6 Bk1b5 1,357-1,375 22.3 0.73 Bk2b5 1,375-1,425 38.3 0.11 Bk2b5 1,425-1,459 40.5 0.23

Soil 7 Bkb6 1,459-1,485 44.0 0.59 Bkb6 1,485-1,505 53.6 0.50

Soil 8 A1b7 1,505-1,540 40.7 0.93 A1b7 1,540-1,575 45.8 0.46 C7 1,575-1,600 65.3 0.10

Somerset Paleosol Bkmb8 1,600-1,638 69.3 0.02 Bk1b8 1,638-1,676 61.8 0.33 Bk2b8 1,676-1,698 55.9 0.34 Bk2b8 1,698-1,720 55.6 0.30 Bk3b8 1,720-1,745 55.3 0.34

Page 276: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

LIST OF FIELD TRIP PARTICIPANTS 1992 SOUTH - CENTRAL FRIENDS OF THE PLEISTOCENE

SAN ANTONIO, TEXAS

James T. Abbot 1502 Westover Road Austin, TX 78703

Whitney J. Autin Louisiana Geological Survey Box G University station Baton Rouge. LA 70893

David l. Amsbury 1422 Brookwood CI. Seabrook, TX 77586

Ann L. Amsbury 1422 Brookwood CI. Seabrook, TX 77586

Saul Aronow Department of Geology Box 10031 Lamar University Station Beaumont, Texas 77710

Joe Artz Office of the State Archaeologist University of Iowa Iowa City, IA 52242

Eric Barnes 5809 Poppleton Omaha, NE 68106

Jon Baskin Department of Geosciences Texas A & I University Kingsville, TX 78363

Scotty D. Baumgartner 2104 San Gabriel # 112 Austin, TX 78705.

Art Bettis Iowa Department of Natural Resources Geological Survey Bureau 123 North Capitol SI. Iowa City, IA 52242

Steve Black Texas Archeological Research Lab Balcones Research Center #5 Austin, TX 78712 - 1100

Martina Bluem Department of Geography University of Texas at Austin Austin, TX 78712

Michael D. Blum Department of Geology Southern Illinois University at Carbondale Carbondale, IL 62901

Britt Bousman Texas Archeological Research Lab Balcones Research Center University of Texas at Austin 10,100 Burnet Road Austin, TX 78758 - 4497

Ken Brown Texas Archeological Research Lab Balcones Research Center 5 University of Texas at Austin 10,100 Burnet Road Austin, TX 78712 - 1100

John Bucksbee 14905 Normandy BLVD Omaha, NE 68123

Scott Burns Department of Geology P.O. Box 751 Portland State University Portland. OR 97207 - 0751

Chris Caran Department of Geology University of Texas at Austin Austin, TX 78712

David Canson Anthropology Department Texas A & M University College Station, TX 77843 - 4352

David Carson Institute of Molecular Medicine University of Texas Health Science Center 15355 Lamda Drive San Antonio, TX 78245

Brian J. Carter 160 Ag. Hall - Agronomy Deptartment Oklahoma State University Stillwater, OK 74059

D. J. (Nick) Cirincione P.O. Box 363 Hurst, TX 76053

Pat Clabaugh Department of Anthropology Archaeological Research Laboratory Texas A & M University College Station, TX 77843 - 4352

Denise Colburn Department of Geosciences Texas A & I University Kingsville, TX 78363

Page 277: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Jo Crosby 2800 July Street # 36 Baton Rouge, LA 70808

Phil Dering Department of Anthropology Texas A & M University College Station, TX 77843

R. F. Diffendal, Jr. 113 Nebraska Hall Universtty of Nebraska - Lincoln Lincoln, NE 68588 - 0517

Joanne Dickenson Route 2 Box 146 KI Portales, NM 88130

D. Bruce Dickson Department of Anthropology Texas A & M university College Station, TX 77843

Jim Dickenson Route 2 Box 146 KI

. Portales, NM 88130

Jeremy S. Dillon Geography - Geology Dllpartment Unr/ersttyof Nebraska - Omaha Omaha, NE 68182 - 0199

Tim Elder 2743 3rd Ave Council Bluffs, IA 51501

John Emerson 820 South Main Warrensburg, MO 64093

C. Reid Ferring P. O. Box 13078 University of North Texas Denton, TX 76203

Ray Fredlund 2800 July Street # 36 Baton Rouge, LA 70808

Wayne Gabriel U.S. Department of Agriculture Soil Conservation Service 1022 Gamer Field Road Uvalde, TX 78801

Emma Day - Gennett 709 E. 31 st Street Bryan TX 77803

Judith Gennett Department of Geology Texas A & M University College Station, TX 77843

Paul Goldberg TARL -BRC#5 University of Texas Austin, TX 78712 - 1100

James Grimes Department of Geography 100 E. Boyd, Rm. 684 Norman, OK 73019

Thomas Guderjan UTSA Institute of Texas Cuttures P.O. Box 1226 San Antonio, TX 78294

Peggy Guccione Geology Department OH - 11 6 Unlverstty of Arkansas Fayetteville, AR 72701

T. C. Gustavson Bureau of Economic Gology University of Texas at Austin Austin, TX 78713

Steve Hall Department of Geography Universtty of Texas at Austin Austin, TX 78712 - 1098·

David M. Hansen 7706 Hascall Street Omaha, NE 68124

Ed Hajic 165 Huckleberry Drive Jackson, VVY 83001

Paul V. Heinrich Dept. of Geology and Geophysics Lousiana State University Baton Rouge, LA 70808

Lynne H. Hehr Geology Department OH - 11 6 University of Arkansas Fayetteville, AR 72701

Page 278: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Vance T. Holliday Department of Geography Science Hall University of Wisconsin Madison, WI 53706

J. Ibanez 2503 Brtdle Path # C Austin, TX 78703

Mischelle Julian 7627 Rambler # 151 Dallas, TX 75231

Donald Lee Johnson Dept. of Geography University of Illinois Urbana, IL 61801

James O. Jones Geology Department Universttyof Texas San Antonio, TX 78249 - 0663

Christopher J. Jurgens Texas Water Development Board P.O. Box 13231 Austin, TX 78711 - 3231

Chrtstine Kellam 303 Cedarbrook Court Austin, TX 78753 - 2107

Anne Kerr 8524 Burnet Rd. Apt: 621 Austin, TX 78758 - 7058

Paul Lehman 2201 Willow Creek No. 205 Austin, TX 78741

Ernest Lundelius, Jr. Vertebrate Paleontology Lab Balcones Research Center 10,100 Burnett Road University of Texas at Austin Austin, TX 78713

Lynn E. Loomis U.S. Department of Agriculture Soil Conservation Service 1022 Garner Field Road Uvalde, TX 78801

Rolfe Mandel Geography - Geology Department University of Nebraska - Omaha Omaha, NE 68182 - 0199

Jennifer Martin 1723 Sheffield Oklahoma City, OK 73120

Joe Bob McHam 1002 Leon Shreveport, LA 71101

Lloyd McKinney Dept. of Rangeland Ecology Texas A & M University College Station, TX 77843 - 2126

Elaine McPherson 807 Northcrest San Antonio, TX 78213

Corey Moffet P.O. Box 1812 Three Rivers, TX 78071

Carol Leah Mueller Geology Dept. OH - 11 6 University of Arkansas Fayetteville, AR 72701

Robert M. Murphy 1002 E. 32nd Ave. Hutchinson, KS 67502

Raymond W. Neck Houston Museum of Natural Science One Hermann Circle Drtve Houston, TX 77030

Joe D. Nichols 3600 Minot Fort Worth, TX 76133

Lee Nordt Soil and Crop Sciences Texas A & M university COllege Station, TX 77843

Gary Parks 3502 N. Salem Road Nickerson, KS

Terry Peck 2129 So. 35th Ave Omaha, NE 68105

Page 279: Late Neogene Fluvial Stratigraphy of Texas Coastal PLain

Donna Porter RRl Box 172 Emmet KS 66422

Ron Ralph Texas Parks and Wildlife Dept. Austin, TX

Gloria Rial 4804 Dodge St. # 4 Omaha, NE 68132

Richard S. Rhodes II Department of Geology UniversHyof Iowa Iowa CHy, IA 52242

Lori Reed 828 Jane Lane Weatherford, TX 76086

Neil E. Salisbury Department of Geography University 01 Oklahoma Norman, OK 73019

Joe Saunders Department of Geoscience NLU Monroe, LA 71209

Holmes A. Semken Department of Geology UniversHyof Iowa Iowa Cny, IA 52242

Sue K. Smith 11888 Longridge Dr., Apt. 1011 Baton Rouge, LA 70816

Cu rt So re nso n Department of Geography 213 Lindley Hall UnversHy of Kansas Lawrence, KS 66045

Gentry Steele Department of Anthropology Texas A & M UniversHy College Station, TX 77843

Donald Stranger 319 Ave A,. No. 11 Plattsmouth, NE 68048

Norman R. Tmord Department of Geology Taxas A & M UniversHy College Station, TX 77843 - 3115

Jet Tilton 1825 Caroline Alice, TX 78332

Pete Thurmond Rt. 1, Box 62B Cheyenne, OK

Alston Thoms

73628

Archaeological Research Lab Texas A & M Universtly College Station, TX 77843

Ralph D. Vinson Route 3, Box 680 - M Whitney, TX 76692

Phillip Amos Ward III 87 - 7 S. University PI. Stillwater, OK 74075

Nancy Washer LSU School of Music 2567 Rhododedron Ave Baton Rouge, LA 70893

Wayne M. Wendland Illinois State Water Survey 2204 Grifftlh Dr. Champaign, IL 61820

Virginia A. Wulfkuhle 231 0 SW Buchanan St. Topeka, KS 66611

Don G. Wyckoff 130 South Sherry Normon, OK 73069