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WALNUT CR

MISSOU

RI R

WAUBONSIE CR

NISHNAB

OTNA R

FISHER CR

MILL CR

MISSOURI R

MISSOURI R

PLUM CR

TABOR

SIDNEY

HAMBURG

RIVERTON

THURMAN

IMOGENE

FARRAGUT

RANDOLPH

rs333

rs2

rs2

£¤275§̈¦29

95°22'30"W

95°22'30"W

95°30'0"W

95°30'0"W

95°37'30"W

95°37'30"W

95°45'0"W

95°45'0"W

95°52'30"W

95°52'30"W

40°52'30"N40°52'30"N

40°45'0"N40°45'0"N

40°37'30"N40°37'30"N

0 2 4 6 81Miles

0 2 4 6 81Kilometers

1:100,000

±

Surficial Geology of Fremont County, Iowa

!

Map LocationQallt

Qpt

Qps

Qwa3

Qal

Correlation of Map Units

Qalfc

AlluvialDeposits

EolianDeposits

GlacialDeposits

Hudson

Wisconsin

Pre-Illinois

QUATERNARY

Holocene

Pleistocene

Title, Author, Agency, Contract and Acknowledgement Information

SURFICIAL GEOLOGY OF FREMONT COUNTY, IOWA

Iowa Geological and Water Survey

Open File Map OFM-12-05 September 2012

prepared by

Stephanie Tassier-Surine1, James Giglierano1, Deborah Quade1, and E. Arthur Bettis, III2

Iowa Geological and Water Survey, Iowa City, Iowa

Iowa Department of Natural Resources, Chuck Gipp, Director Iowa Geological and Water Survey, Robert D. Libra, State Geologist

Supported in part by the U.S. Geological Survey Cooperative Agreement Number G11AC20247

National Cooperative Geologic Mapping Program (STATEMAP)

ACKNOWLEDGMENTS Recognized for contributions to production of the map: Andrew Asell, Chris Kahle, Casey Kohrt, Brian Witzke, Ray Anderson, Bill Bunker, and Mary Pat Heitman. New subsurface geologic data was mostly generated by Michael Bounk of the Iowa Geological and Water Survey (IGWS). Jason Vogelgesang (IGWS) and Carolyn Koebel (University of Iowa) prepared well samples for stratigraphic logging. 1Iowa Geological and Water Survey, Iowa City, Iowa 52242 2Department of Geoscience, The University of Iowa, 121 Trowbridge Hall, Iowa City, Iowa 52242

Introduction to the Surficial Geology of Fremont County, Iowa

Fremo nt Co unty lies within the Southern Iowa Drift Plain (Prio r and Kohrt, 2006) land fo rm region o f Iowa. Su rficial materials co nsis t of a mix of eol ian depos its (loess), glacial t ill outcrop , and al luv ium. Multip le periods of Quaternary glaciatio n and subaerial erosion have led to the lan dscape we see tod ay. General ly speaking , the map area cons ists of lo ess of variable thick ness ov erly ing Pre-Il lin ois glacial sed iments. T hese dep osi ts are regional ly exten sive.

Previo us surficial geolo gic mapping o f th e area is limited to th e Des Moines 4 o x 6 o Q uad ran gle at a scale of 1 :1,00 0,000 (Hallberg et al ., 19 91). Compilat ion mapp ing near the project area in Ad ams Co unty was completed in 2010 (Tassier-Surine et al.). U dden (190 2) fi rst describ ed and mapp ed the Quaternary geo logy of Fremont Cou nty and d iscussed the stratigraphy of the Pennsy lvanian and Cretaceo us strata that co mprise the county’s bedrock units. Statew ide bed ro ck geo logic map s by Hershey (1 969), and mo st recent ly, by Witzke, Anderso n, and Pope (20 10), depict the increased understandin g o f the distribut ion of geo log ic un its at the bed ro ck surface across this regio n, includin g Fre mont Co unty.

Early researchers bel ieved there were only two episodes o f Pre-Illinois glaciat ion in Iow a: Kansan and Nebraskan (Chamberlin, 1 894, 1 895; Bain, 1 896; Shimek, 19 09; Kay and Ap fel, 1 928; Ruh e, 19 69). Later regional studies determin ed that the o rigin al concept o f Kansan-Afto nian-Nebraskan was gross ly o vers implified and flawed. It is now reco gnized that there w ere at least seven episo des of Pre-Ill ino is glaciation that occurred in th is regio n from app ro ximately 2. 2 to 0.5 mil lio n years ago (Boellstorff, 1978 a, 1978 b; Hallberg, 198 0a, 1986 ). Episod ic erosio n d uring the last 500 ,000 years has led to the destruct ion of p re-exis tin g g lacial lan dforms asso ciated with these glaciations. Boells torff (1978a, 1978b) and Hallberg (198 0a, 198 0b, 1 986) u ndertook regional-scale projects that invo lved detailed ou tcrop an d subsurface invest igatio ns inclu din g extens ive laborato ry work and sy nthesis o f p rev ious studies. These s tud ies led to the abandon ment of th e classic glacial and interglacial terminology: Kansan, Aftonian, and Neb raskan. This stu dy mark ed a sh ift from the use o f t ime-strat igraph ic terms to li tho stratigrap hic class ification. The resul t of Boells torff’s and Hallberg’s s tud ies was the develo pment o f a li thos tratig raph ic framewo rk for Pre-Illinois til l. They developed a general s trat igraph ic framework for Iowa and eastern Nebraska b ased on phys ical s tratig rap hy, mineralog ic criteria as well magneto stratigrap hy and teph roch ro nolo gy. In western Iowa and eastern Nebraska three li tho logical ly d ist inctive ti ll assemb lages were iden tified as the ‘A’, ‘B’, and ‘C’ t ills with p aleo sols sometimes d el imiting mu ltiple til l uni ts within the A and B ti ll assemblages. Recent wo rk b y Balco an d Rovey (2010 ) su ggests that a single ice advance around 2. 4 Ma depos ited the C til l and that the A and B t ill assemb lages accumulated between abo ut 1 .3 and 0. 5*Ma.

The Lo veland Loess (Daniels and Handy, 19 59; Ruhe, 196 9; Bet tis , 1 990) is the o nly Ill inois or late middle Plesi tocene depo sit that is current ly reco gnized in western Iowa. Where o bserved in outcrop , the Sangamon Geosol is develo ped in the upper p art o f the Lovelan d. The Lovelan d Loess thins away from the Misso uri Riv er and the Sanga mon Geosol merges with the thick and more weath ered Y armouth-Sangamon G eo sol in southern Iowa (Ru he, 1967 ).

In Fremont Co unty, the hig hly ero ded and dissected Pre-Ill inois u pland and o lder terraces are mantled by W iscons in loesses of variable thickness (Ru he, 196 9; Prior, 1976). The Wisco nsin loesses are the yo ungest regional ly extens ive Quaternary materials and were d ep osited between 30,0 00 and 12 ,000 years ago. Two loess uni ts were depo sited across Iowa during Wisconsin time, the older Pisgah Formation and the yo unger Peo ria Loess . The Pisgah is thin and inclu des loess and related slo pe sediments that have been altered by col luv ial hillslo pe processes, pedo gen ic and periglacial processes. T he upper part of the un it is mo dified by develop ment of the Farmdale Geosol. It is not uncommon to see the Farmdale develo ped throug hout the Pisgah and inco rp orated into the und erlying older Sangamo n Geo sol. Th e Pisgah Fm. loess was deposi ted on the western Io wa land scape from about 55, 000 to 26, 000 years ag o (Bett is et al., 2003). The Pisgah Fo rmatio n is typ ical ly b uried b y Peo ria Formation loess . The Peoria Fo rmation loess accumu lated on stable landsurfaces in western Iowa from 23,000 to 12, 000 years ago.

Surficial deposi ts o f the map area are co mp osed o f four formation s: DeForest, Noah Creek, Peoria and und ifferent iated Pre-Illinois t il ls. Hudson age depo sits associated with fine-grained alluvial and col luvial sediments includ e the DeFores t Fo rmation which is subd ivid ed into the Camp Creek, Roberts Creek , Gunder and Corrington members . T he Noah Creek Formation includes coarser g rained d epo sits asso ciated w ith large valleys which are o verlain b y finer-grained alluvial material or eolian sil t and sand. Peoria Formation eo lian materials cons ist o f wind-blo wn si lt that may be up to 175 feet in th ickness . Limited areas o f eol ian sand may b e present adjacent to river v al leys. Ad dit ional eo lian materials may b e intermittent ly p resent mantlin g Wiscon sin E piso de terraces. Pre-Ill inois glacial depo sits are exposed in the map area alo ng drainages and where loess cover is thin. Based on existing well data, Pre-Ill ino is d eposits may be as thick as 350’ in bedrock val leys.

So ils series u nits fro m the Soil Survey of Fremo nt County, Iowa (Clark and N ixon, 1975) were categorized into surficial geo log ic units based on soil d ata an d available subsurface geologic data from the Io wa Geolo gical and Water Survey ’s GE OSAM database (water well log database) as w ell as o ther exis ting subsurface data for this co mp ilation map p ro ject. Modeling and mapp ing of th e glacial t il l ou tcrops w as comp leted us ing ArcGIS 10 .0, g vSIG open source G IS prog ram and the Sextante land scap e classification subprogram.

* We disagree w ith the y ounger 0 .2Ma age es timate for Pre-Il lino is glaciatio ns presented b y Balco and Ro vey

(2010 ) and su ggest 0 .5Ma is more co nsistent with regional data and s trat igraph ic relat ionship s.

References

Bain, H.F., 1896, Relations of the Wisconsin a nd K ansas drift sheets in c ent ral Iow a, a nd relate d phe nome na: Iow a Geological Survey

Annua l Re port v. 6, p. 429-476. Balco, G. and Rove y II , C.W., 2010, Absolute chronology for ma jor Ple ist oc ene a dvances of the La urent ide Ice Sheet: G eology, v. 38

p. 795-798. Bettis, E .A., I II , 1990, Holocene alluvial stratigraphy of western Iow a, in Bettis, E .A. I II e d., Holoce ne a lluvial stratigraphy and

se lected aspe cts of the Quaternary history of western Iow a: Midwest Friends of the Pleistocene Field Trip G uidebook, p. 1-72.

Bettis III, E.A., Muhs, D.R., Robert s, H.M., and Wintle. A.G., 2003, La st glac ial loe ss in the conterminous U.S.A.: Quaternary Scienc e Reviews, v. 22, p. 1907-1946.

Boellstorff, J., 1978a, North Americ an Pleistocene Stages reconsidere d in l ight of probable Plioc ene-Pleistocene c ontine nta l glac ia tion: Science, v. 202, p. 305-307.

Boellstorff, J., 1978b, Chronology of some late Ce nozoic de posits from t he ce ntral Unit ed St ates and the ice ages: Transa ctions of the Nebraska Academy of Sc ie nce , v. 6, p. 35-49.

Cha mberla in, T.C., 1894, in Ge ikie, J. (ed.) The Great Ic e Age 3rd edition, p. 753-764. Stanford, London. Cha mberla in, T.C., 1895, The classifica tion of America n glacia l deposits: Journal of Geology, v. 3, p. 270-277. Clark, L.A. and N ixon, J.R., 1975, Soil Surve y of Fre mont County, Iowa: Unit ed Sta tes Department of Agriculture, S oil Conservat ion

Service, 104p. Daniels, R.B. and H andy, R.L., 1959, Sugge ste d new type sect ion for the Loveland Loess in western Iow a: Journa l of G eology, v. 67,

p. 114-119. Ha llberg, G.R., 1980a, Pleistocene st ratigraphy in east-c entral Iowa: Iowa G eological Surve y Technic al Information Series 10, 168p. Ha llberg, G .R., 1980b, I llinoian and Pre-Illinoia n stratigraphy of southe ast Iowa and adjace nt I llinois: Iowa Ge ologic al Survey

Technical Information Se ries 11, 206p. Ha llberg, G.R., 1986, Pre-Wisconsin glacia l stratigraphy of the centra l plains re gion in Iowa, Nebraska, K ansa s, and Missouri: in

Ric hmond, G .M. and Fuller ton, D.S., eds., Q uate rna ry Glac ia tions in the Unite d S tates of Americ a, Report of the Int ernationa l Correlat ion Programme-Project 24: in Sibrava, V., Bowen, D.Q., and Richmond, G .M., eds., Q uate rnary Scienc e Reviews, Q ua ternary Glac iations in the Northern He misphere, v. 5, p. 11-15.

Ha llberg, G.R., Line bac k, J.A., Mickelson, D.M., Knox, J.C., Goebe l, J.E., Hobbs, H .C., Whitf ield, J.W., Ward, R.A., Boellstorf, J.D., and Swinehart , J.B., 1991, Q uate rnary ge ologic map of the Des Moines 4° x 6° qua drangle, U nited Stat es: U.S. Geological Survey, Miscellaneous Investigat ions S eries, Map I-1420, 1:100,000 sca le map sheet .

Hershe y, H.G., 1969, Geologic Ma p of Iowa , 1:500,000, Iowa Geological Survey, Iow a City. Kay, G.F. and Apfel, E.T., 1928, The Pre-Illinoian Pleistocene geology of Iowa: Iowa Geological Survey Annual Report v. 34, p. 1-

304. Prior , J.C., 1976, Landforms of Iowa: Iowa City, University of Iowa Pre ss, 154 p. Prior , J.C. and Korht, C.J., 2006, The Landform Re gions of Iowa , Iowa Geologica l Survey, digital map, a vaila ble on IDNR GIS

Library- f tp:// ftp.igsb.uiowa.edu/gis_libra ry/ ia_sta te/geologic /landform/la ndform_regions.zip; http://www .igsb.uiowa.edu/nrgislibx/

Ruhe, R.V., 1969, Quat ernary Landsc ape s in Iowa , Iowa St ate Universit y Press, Ames, Iowa, 255p. Ruhe, R.V., D anie ls, R.B., and Ca dy, J.G., 1967, Landscape evolution a nd soil formation in southw estern Iow a, U.S. De partme nt of

Agricult ure Tec hnical Bulletin 1349, 242p. Shimek, B., 1909, Aftonian sand and gra vels in we stern Iowa: Bullet in of the Geological Societ y of Ame rica, v. 20, p. 399-408. Ta ssier-Surine, S.A., Giglie rano, J.D., Quade , D .J., and Bettis, E.A., III, 2011, Surfic ia l Geology of Ada ms Count y, Iowa : Iow a

Geological and Wat er Survey O pen File Map OFM-11-9, 1:50,000 scale ma p sheet. Udde n, J.A., 1916, Geology of Mi lls and Fremont Counties: Iowa Geologica l Survey Annual Report, v. 13, p. 123-182. Witzke, B.J., Anderson, R.R., and Pope, J.P., 2010, Bedrock Geologic Map of Iow a, scale: 1:500,000: Iowa Geologica l and Water

Survey, Ope n File D igital Map O FM-10-1.

LEGEND

CENOZOIC

QUATERNARY SYSYTEM

HUDSON EPISODE Qal - Alluvium (DeFo rest Formatio n-U ndifferentiated) Variable th ickness of less than 1 to 5 m (3-16 ft) of very dark gray to brow n, no ncalcareous to calcareo us, strati fied sil ty clay loam, clay loam, loam to sandy loam al luv ium and colluviu m in stream valleys, o n hill s lop es and in closed depress ions. May overlie Pre-Illinoain g lacial til l of the Wo lf Creek or Alb urnett fo rmatio ns o r Pre-Holocene fine-grained alluviu m. Associated with low-rel ief mo dern flood plain , closed depressions, mo dern drainageways or to es lope p osi tio ns o n the landscape. U nit also includ es colluvial depos its derived from adjacent map units. Seasonal high water table and potent ial for frequent flood ing. Qalfc – Missouri River Va lley – Flo od Ba sin/Channel Belt (DeForest Formatio n- Undifferentiated ) Variab le th ickness of 3 to 10 m (10-33 ft) of very d ark gray to b rown, calcareo us to no ncalcareous, mass ive to strati fied si lty clay loam to loam to sand y loam alluv ium and col luvium in the Missouri River val ley. Alluvium overlies a thick (3-35 m; 1 0-115 ft) sequence o f med ium sand to pebbly sand outw ash o f the Noah Creek Formation. Associated with lo w-rel ief mod ern floodp lain. Season al hig h water table and poten tial fo r frequent flood ing. Qallt – River Channel Belt – Low Terrace (DeFo res t Formation-Camp Creek Mbr. and Roberts Creek Mbr.) Variable th ickness o f less than 1 to 5 m (3-16 ft ) o f very dark gray to bro wn, noncalcareo us, st rat ified si lty clay loam, loam, or clay loam, associated with the mo dern channel belt of the West Nishnabo tna and East Nishnabotna river valleys. O verl ies Pre-H olocene fine-grained al luvium. Occupies lowest pos ition o n the floodp lain ie. mod ern and historic channel belts . Ox-bo w lakes and meander scars are common features asso ciated with this terrace level. Map ped p rimarily using aerial imagery and county soi l survey data. Seasonal hig h water tab le and frequent flood ing potent ial.

HUDSON AND WISCONSIN EPISODE

WISCONSIN EPISODE Qpt- Loess Mantled Terrace (Peoria Fo rmatio n – sil t and/or san d facies) 2 to 7 m (7-23 ft) o f yello wish brow n to gray, massive, jointed , calcareous or no ncalcareous, silt loam and intercalated fine to mediu m, well sorted, sand . May grade d ownward to poo rly to mod erately well sorted, mo derately to w ell strati fied, co arse to fine feldspathic quartz san d, lo am, o r si lt loam al luvium (Late Phase Hig h Terrace) or may overlie a Farmdale Geoso l develo ped in Pisg ah Silt wh ich in turn overlies a well-expressed Sang amon Geoso l d eveloped in poorly to mod erately well so rted , mo derately to well s tratified, coarse to fine sand, lo am, or s ilt loam allu viu m (Early Phase High Terrace). Qps – Loess (Peoria Formatio n—silt facies ) Generally 3 to 50 m (1 0 to 164 ft) of yellow ish to g rayish brown, mass ive, jointed calcareo us or noncalcareous sil t loam to s il ty clay loam. D ep osits are thickest in the wes tern port ion of the cou nty in the Loess Hil ls landform reg ion and th in to the east . L imited areas of fine eo lian sand may be present near majo r river v al leys. O verl ies a grayish brown to olive gray sil ty clay loam to s il ty clay (Pisgah Formation—erod ed Farmd ale Geosol) which is less than 1.5 m (5 ft) th ick . The Farmd ale may be welded to an older Sangamo n Geosol develo ped in loamy glacial til l of the Wo lf Creek or Alb urnett formations . T his map ping unit encompasses upland divides, rid getops and con vex sideslop es . Well to somewhat poorly drained landscape.

PRE-ILLINOIS EPISODE Qwa3 – Till (Wo lf Creek o r Alburnett fo rmatio ns) General ly 15 to 1 00 m (49-32 8 ft ) of very d en se, massive, fractured, lo amy glacial ti ll of the Wo lf Creek or A lburnett formatio ns with or without a thin loess mantle (Peoria Formation—less than 2 m) an d interven ing clayey Farmdale/San gamon Geo sol . This mapp ing u nit enco mpasses narro wly d issected interfluves and s ide slo pes, and side val ley slo pes. Drainage is v ariable from w ell drained to poo rly drained.

Other Mapping Units Qpq - Pits and Quarries Sand and gravel pits and rock q uarries. Extent mapped as shown in co unty so il surveys and as identified on aerial imagery. Wa ter Features Rivers , lak es and small po nds fo rmed by blockage of d rainagew ay s and riv er channels. Extent map ped as sh own in county so il surveys and as ident ified o n aerial imagery. Dril l Holes

Base map from iowa DOT Road Map Layers 2009. Shaded relief from Iowa Lidar Project 2007-2011. FremontCo_SurficialGeology2012.mxd, version 10/16/12 (ArcGIS 10.0)

Map projection and coordinate system based on Universal Transverse Mercator (UTM) Zone 15, datum NAD83.The map is based on interpretations of the best available information at the time of mapping. Map interpretations are not a substitute for detailed site specific studies.