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GLENWOOD

MALVERN

PACIFIC JUNCTIONHASTINGS

EMERSON

SILVER CITY

HENDERSON

KEG CR

MISSO

URI R

IN DIAN CR

MISSOURI R

MUD CR

MISSOURI R

rs92rs370

£¤59

£¤34

rs92rs370

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

41°7'30"N41°7'30"N

41°0'0"N41°0'0"N

0 2 4 6 81 Miles

0 2 4 6 81Kilometers

1:100,000

±

Surficial Geology of Mills County, Iowa

!

Map Location

Qallt

Qpt

Qps

Qwa3

Qal

Correlation of Map Units

Qalfc

AlluvialDeposits

EolianDeposits

GlacialDeposits

Hudson

Wisconsin

Pre-Illinois

QUATERNARY

Holocene

Pleistocene

Base map from iowa DOT Road Map Layers 2009. Shaded relief from Iowa Lidar Project 2007-2011. MillsCo_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.

Title, Author, Agency, Contract and Acknowledgement Information

SURFICIAL GEOLOGY OF MILLS COUNTY, IOWA

Iowa Geological and Water Survey

Open File Map OFM-12-08 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 Mills County, Iowa

Mills Co unty lies with in the So uthern Io wa D rift Plain (Prior and Kohrt, 2006 ) landform reg ion o f Io wa. Surficial materials cons ist of a mix o f eo lian d ep osits (lo ess), glacial ti ll o utcrop, and alluv ium. Mult iple p eriods of Quaternary glaciatio n and subaerial eros ion have led to the landscape we see today. G enerally speak ing, the map area co nsis ts of loess o f variable th ickness overly ing Pre-Ill inois glacial sediments. These depos its are regio nally extens ive.

Previo us surficial geo logic mapping o f the area is l imited to the Des Mo ines 4 o x 6 o Quadrangle at a scale o f 1:1,000 ,000 (Hallb erg et al., 1991 ). Comp ilat ion mapp ing near the p ro ject area in Adams County w as co mpleted in 201 0 (Tass ier-Surine et al. ). Udden (19 02) first described and mapp ed th e Quaternary geology of Mil ls Co unty and d iscussed the s tratig raph y of the Pennsylv an ian and Cretaceo us s trata that co mp rise the cou nty’s bedrock un its. Statewide bedrock geologic maps by Hershey (1 969), and mo st recent ly, b y Witzke, Anderson, and Pope (2010 ), depict the increased understand ing o f the dis tribut io n of geolog ic units at the b edro ck surface across this region , including Mills County.

Early researchers believed there were only two episodes o f Pre-Ill ino is glaciation in Iowa: Kansan and Nebraskan (Chamberlin, 189 4, 18 95; Bain, 1896; Shimek, 19 09; Kay and Apfel, 1 928; Ru he, 1969 ). 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 p hysical stratigraphy, mineralo gic criteria as well as magneto stratigraphy and teph roch ro nolo gy. In western Io wa and eas tern Nebraska three l itho logical ly dis tinct ive t il l assemblages were iden tified as the ‘A’, ‘B’, and ‘C’ til ls, with p aleosols sometimes d el imiting multiple til l units with in 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, 1959 ; Ruh e, 196 9; Bett is, 199 0) is the on ly Il lino is or late middle Plesitocene depo sit that is current ly reco gnized in western Iowa. Where o bserved in ou tcro p, the Sangamon Geoso l is develop ed in the upp er part of the Loveland. The Loveland Loess thins away from th e Missouri River and the Sangamo n Geoso l merges with the th ick and more weathered Yarmouth-Sangamon Geosol in southern Iowa (Ruhe, 196 7).

In Mills Coun ty, th e highly eroded and d issected Pre-Il lino is up land and old er terraces are mantled b y Wisco nsin loesses of variab le thick ness (Ruhe, 196 9; Prior, 197 6). 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 Farmd ale 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 depo sits o f the map area are comp osed of four fo rmatio ns: D eForest, Noah Creek, Peoria and und ifferent iated Pre-Ill ino is t ills . Hud son age depo sits asso ciated with fine-grained al luvial 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 of wind-blow n si lt that may be up to 4 6 meters (1 50 feet) in thick ness. Limited areas of eol ian sand may be present adjacent to river valleys . Add itio nal eol ian materials may be intermit tent ly present mantling Wiscon sin Episode terraces. Pre-Ill ino is g lacial depos its are expo sed in the map area alo ng d rainages and wh ere lo ess cover is th in. Based o n exist ing well d ata, Pre-Illinois depos its may be as th ick as 40 0’ in b ed ro ck valleys .

So il series u nits fro m the Soil Survey o f Mills Co unty , Io wa (Nixon, 19 82) were categorized into surficial geologic units based o n soil data an d availab le subsurface geologic data from the Iowa Geo logical and Water Survey’s GEOSAM d atabase (water well log database) as well as other exis tin g sub surface data fo r this compilat ion map project. Mod eling and mapping of the glacial ti ll o utcrops was comp leted us ing ArcGIS 10.0, gvSIG open source GIS program, and the Sextante landscape class ificatio n sub program.

* We d isagree with the you nger 0.2 Ma age es timate for Pre-Il lino is glaciations presented b y Balco and

Rovey (201 0) and suggest 0.5 Ma is more cons istent with regio nal data and stratig rap hic relatio nships.

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. 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. Nixon, J.R., 1982, Soil Survey of Mills Count y, Iowa: Unit ed Sta tes Department of A griculture, S oil Conservat ion Se rvice, 163p. 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 rest Formation-Camp Creek Mbr. and Roberts Creek Mb r. ). 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 modern chann el belt of the West Nish nabotna River valley. Overlies Pre-Holocene fin e-grain ed al luvium. Occupies lowest p osi tio n on the floo dplain ie. modern and histo ric channel belts . Ox-bow lakes and meander scars are co mmon features associated w ith th is terrace lev el . Map ped p rimarily us ing aerial imagery and co unty soi l survey data. Seasonal h igh water tab le and frequent flooding p otent 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 45 m (1 0 to 148 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 uni t 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 20 m (49-39 4 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