https://ir.uiowa.edu/igs_ofm/1104/thumbnail.jp

Bettis, E Authur, III

Giglierano, James

Quade, Deborah

Tassier-Surine, Stephanie

English

Iowa Research Online

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£¤59
rs44
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HARLAN
SHELBY
IRWIN
TENNANT ELK HORN
EARLING
DEFIANCE
PANAMA
PORTSMOUTH
KIRKMAN
WESTPHALIA
95°7'30"W
95°7'30"W
95°15'0"W
95°15'0"W
95°22'30"W
95°22'30"W
95°30'0"W
95°30'0"W
41°52'30"N
41°52'30"N
41°45'0"N
41°45'0"N
41°37'30"N
41°37'30"N
41°30'0"N
41°30'0"N
0 2 4 6 81 Miles
0 2 4 6 81 Kilometers
1:100,000
Surficial Geology of Shelby County, Iowa
!
Map Location
Qallt
Qpt
Qps
Qwa3
Qal
Correlation of Map Units
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. 
Shelby_SFGeology.mxd, version 9/22/13  (ArcGIS 10.1)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 SHELBY COUNTY, IOWA  Iowa Geological and Water Survey Open File Map OFM-13-8 September 2013  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 G12AC20280 National Cooperative Geologic Mapping Program (STATEMAP)   ACKNOWLEDGMENTS   Recognized for contributions to production of the map:   Chris Kahle, Casey Kohrt, and Mary Pat Heitman.  New subsurface geologic data was mostly generated by Michael Bounk of the Iowa Geological and Water Survey (IGWS).  Jason Vogelgesang and Carolyn Koebel of IGWS prepared well samples for stratigraphic logging.  Paul VanDorpe (IGWS) provided editorial review.    1Iowa Geological and Water Survey, Iowa City, Iowa  52242 2Department of Earth and Environmental Sciences, The University of Iowa, 121 Trowbridge Hall, Iowa City, Iowa  52242   
Introduction to the Surficial Geology of Shelby County, Iowa   Shelby County lies within the Southern Iowa Drift Plain (Prior and Kohrt, 2006) landform region of Iowa.  Surficial materials consist of a mix of eolian deposits (loess), glacial till outcrop, and alluvium.  Multiple periods of Quaternary glaciation and subaerial erosion have led to the landscape we see today.  Generally speaking, the map area consists of loess of variable thickness overlying Pre-Illinois glacial sediments.  These deposits are regionally extensive.  Previous surficial geologic mapping of the area is limited to the Des Moines 4 o x 6 o Quadrangle at a scale of 1:1,000,000 (Hallberg et al., 1991).  Compilation mapping was completed near the project area in 2011 and 2012 for Adams County (Tassier-Surine et al., 2011), Mills County (Tassier-Surine et al., 2012a), and Montgomery County (Tassier-Surine et al., 2012b).  Statewide bedrock geologic maps by Hershey (1969), and most recently, by Witzke, Anderson, and Pope (2010), depict the increased understanding of the distribution of geologic units at the bedrock surface across this region, including Shelby County. Early researchers believed there were only two episodes of Pre-Illinois glaciation in Iowa: Kansan and Nebraskan  (Chamberlin, 1894, 1895; Bain, 1896; Shimek, 1909; Kay and Apfel, 1928; Ruhe, 1969).  Later regional studies determined that the original concept of Kansan-Aftonian-Nebraskan was grossly oversimplified and flawed.  It is now recognized that there were at least seven episodes of Pre-Illinois glaciation that occurred in this region from approximately 2.2 to 0.5 million years ago (Boellstorff, 1978a, 1978b; Hallberg, 1980a, 1986).  Episodic erosion during the last 500,000 years has led to the destruction of pre-existing glacial landforms associated with these glaciations.  Boellstorff (1978a, 1978b) and Hallberg (1980a, 1980b, 1986) undertook regional-scale projects that involved detailed outcrop and subsurface investigations including extensive laboratory work and synthesis of previous studies.  These studies led to the abandonment of the classic glacial and interglacial terminology: Kansan, Aftonian, and Nebraskan.  This study marked a shift from the use of time-stratigraphic terms to lithostratigraphic classification. The result of Bollestorf’s and Hallberg’s studies was the development of a lithostratigraphic framework for Pre-Illinois till.  They developed a general stratigraphic framework for Iowa and eastern Nebraska based on physical stratigraphy, mineralogic criteria as well magnetostratigraphy and tephrochronology.   In western Iowa and eastern Nebraska three lithologically distinctive till assemblages were identified, the ‘A’, ‘B’, and ‘C’ tills with paleosols sometimes delimiting multiple till units within the A and B till assemblages.  Recent work by Balco and Rovey (2010) suggests that a single ice advance around 2.4 Ma deposited the C till and that the A and B till assemblages accumulated between about 1.3 and 0.5*Ma.  The Loveland Loess (Daniels and Handy, 1959; Ruhe, 1969; Bettis, 1990) is the only Illinois or late middle Plesitocene deposit that is currently recognized in western Iowa.  Where observed in outcrop, the Sangamon Geosol is developed in the upper part of the Loveland.  The Loveland Loess thins away from the Missouri River and the Sangamon Geosol merges with the thick and more weathered Yarmouth-Sangamon Geosol in southern Iowa (Ruhe, 1967).   In Shelby County, the highly eroded and dissected Pre-Illinois upland and older terraces are mantled by Wisconsin loesses of variable thickness (Ruhe, 1969; Prior, 1976).  The Wisconsin loesses are the youngest regionally extensive Quaternary materials and were deposited between 30,000 and 12,000 years ago.  Two loess units were deposited across Iowa during Wisconsin time, the older Pisgah Formation and the younger Peoria Formation.  The Pisgah is thin and includes loess and related slope sediments that have been altered by colluvial hillslope processes, pedogenic and periglacial processes.  The upper part of the unit is modified by development of the Farmdale Geosol. It is not uncommon to see the Farmdale developed throughout the Pisgah and incorporated into the underlying older Sangamon Geosol. The Pisgah Formation loess was deposited on the western Iowa landscape from about 55,000 to 26,000 years ago (Bettis et al., 2003) and is typically buried by Peoria Formation loess.  The Peoria Formation loess accumulated on stable landsurfaces in western Iowa from 23,000 to 12,000 years ago.   Surficial deposits of the map area are composed of four formations:  DeForest, Noah Creek, Peoria and undifferentiated Pre-Illinois tills.  Hudson age deposits associated with fine-grained alluvial and colluvial sediments include the DeForest Formation which is subdivided into the Camp Creek, Roberts Creek, Gunder and Corrington members.  The Noah Creek Formation includes coarser grained deposits associated with large valleys which are overlain by finer-grained alluvial material or eolian silt and sand.  Peoria Formation eolian materials consist of wind-blown silt that may be up to 15 m (50 ft) in thickness.  Limited areas of eolian sand may be present adjacent to river valleys.  Additional eolian materials may be intermittently present mantling Wisconsin Episode terraces.  Pre-Illinois glacial deposits are exposed in the map area along drainages and where loess cover is thin.  Based on existing well data, Pre-Illinois deposits may be as thick as 137 m (450 ft) in bedrock valleys. Soils series units from the Soil Survey of Shelby County, Iowa (Jury et al., 1961) were categorized into surficial geologic units based on soil data and available subsurface geologic data from the Iowa Geological and Water Survey’s GEOSAM database (water well log database) as well as other existing subsurface data for this compilation map project.  Modeling and mapping of the glacial till outcrops was completed using ArcGIS 10.1, Quantum open source GIS program and the terrain classification command within the GRASS plugin.   * We disagree with the younger 0.2Ma age estimate for Pre-Illinois glaciations presented by Balco and Rovey (2010) and suggest 0.5Ma is more consistent with regional data and stratigraphic relationships.   References  Bain, H.F., 1896, Relations of the Wisconsin and Kansas drift sheets in central Iowa, and related phenomena:  Iowa Geological Survey Annual Report v. 6, p. 429-476.  Balco, G. and Rovey II, C.W., 2010, Absolute chronology for major Pleistocene advances of the Laurentide Ice Sheet: Geology, v. 38 p. 795-798.   Bettis, E.A., III, 1990, Holocene alluvial stratigraphy of western Iowa, in Bettis, E.A.  III ed., Holocene alluvial stratigraphy and selected aspects of the Quaternary history of western Iowa:  Midwest Friends of the Pleistocene Field Trip Guidebook, p. 1-72.  Bettis III, E.A., Muhs, D.R., Roberts, H.M., and Wintle. A.G., 2003, Last glacial loess in the conterminous U.S.A.:  Quaternary Science Reviews, v. 22, p. 1907-1946. Boellstorff, J., 1978a, North American Pleistocene Stages reconsidered in light of probable Pliocene-Pleistocene continental glaciation:  Science, v. 202, p. 305-307.  Boellstorff, J., 1978b, Chronology of some late Cenozoic deposits from the central United States and the ice ages:  Transactions of the Nebraska Academy of Science, v. 6, p. 35-49. Chamberlain, T.C., 1894, in Geikie, J. (ed.) The Great Ice Age 3rd edition, p. 753-764. Stanford, London.  Chamberlain, T.C., 1895, The classification of American glacial deposits:  Journal of Geology, v. 3, p. 270-277. Daniels, R.B. and Handy, R.L., 1959, Suggested new type section for the Loveland Loess in western Iowa:  Journal of Geology, v. 67, p. 114-119. Hallberg, G.R., 1980a, Pleistocene stratigraphy in east-central Iowa:  Iowa Geological Survey Technical Information Series 10, 168p. Hallberg, G.R., 1980b, Illinoian and Pre-Illinoian stratigraphy of southeast Iowa and adjacent Illinois:  Iowa Geological Survey Technical Information Series 11, 206p. Hallberg, G.R., 1986, Pre-Wisconsin glacial stratigraphy of the central plains region in Iowa, Nebraska, Kansas, and Missouri:  in Richmond, G.M. and Fullerton, D.S., eds., Quaternary Glaciations in the United States of America, Report of the International Correlation Programme-Project 24:  in Sibrava, V., Bowen, D.Q., and Richmond, G.M., eds., Quaternary Science Reviews, Quaternary Glaciations in the Northern Hemisphere, v. 5, p. 11-15. Hallberg, G.R., Lineback, J.A., Mickelson, D.M., Knox, J.C., Goebel, J.E., Hobbs, H.C., Whitfield, J.W., Ward, R.A., Boellstorf, J.D., and Swinehart, J.B., 1991, Quaternary geologic map of the Des Moines 4° x 6° quadrangle, United States:  U.S. Geological Survey, Miscellaneous Investigations Series, Map I-1420, 1:100,000 scale map sheet. Hershey, H.G., 1969, Geologic Map of Iowa, 1:500,000, Iowa Geological Survey, Iowa City. Jury, J.M., Slusher, D.F., and Smith, S.M., 1961, Soil Survey of Shelby County, Iowa:  United States Department of Agriculture, Soil Conservation Service, 61p, 96 map sheets. 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 Press, 154 p. Prior, J.C. and Korht, C.J., 2006, The Landform Regions of Iowa, Iowa Geological Survey, digital map, available on IDNR GIS Library- ftp://ftp.igsb.uiowa.edu/gis_library/ia_state/geologic/landform/landform_regions.zip; http://www.igsb.uiowa.edu/nrgislibx/ Ruhe, R.V., 1969, Quaternary Landscapes in Iowa, Iowa State University Press, Ames, Iowa, 255p. Ruhe, R.V., Daniels, R.B., and Cady, J.G., 1967, Landscape evolution and soil formation in southwestern Iowa, U.S. Department of Agriculture Technical Bulletin 1349, 242p. Shimek, B., 1909, Aftonian sand and gravels in western Iowa:  Bulletin of the Geological Society of America, v. 20, p. 399-408. Tassier-Surine, S.A., Giglierano, J.D., Quade, D.J., and Bettis, E.A., III, 2011, Surficial Geology of Adams County, Iowa:  Iowa Geological and Water Survey Open File Map OFM-11-9, 1:50,000 scale map sheet. Tassier-Surine, S.A., Giglierano, J.D., Quade, D.J., and Bettis, E.A., III, 2012a, Surficial Geology of Mills County, Iowa:  Iowa Geological and Water Survey Open File Map OFM-12-8, 1:100,000 scale map sheet. Tassier-Surine, S.A., Giglierano, J.D., Quade, D.J., and Bettis, E.A., III, 2012b, Surficial Geology of Montgomery County, Iowa:  Iowa Geological and Water Survey Open File Map OFM-12-9, 1:100,000 scale map sheet. Witzke, B.J., Anderson, R.R., and Pope, J.P., 2010, Bedrock Geologic Map of Iowa, scale: 1:500,000:  Iowa Geological and Water Survey, Open File Digital Map OFM-10-1.  
LEGEND    CENOZOIC  QUATERNARY SYSYTEM  HUDSON EPISODE  Qal - Alluvium (DeFo rest  Formation-Undifferentiated) Variable th ickness of less  than 1  to 5 m (3-16 ft) of very  dark gray to brown, noncalcareous  to calcareous, strati fied  sil ty clay  loam, clay loam, loam to sandy loam al luv ium and colluvium in stream valleys,  on hill  s lopes  and  in closed depress ions.  May overlie Pre-Illinoain g lacial til l of the Wolf Creek or Alburnett fo rmations o r Pre-Holocene fine-grained alluvium. Associated  with low-rel ief modern  floodplain , closed  depressions,  modern  drainageways  or to es lope posi tions on the landscape. U nit also includes  colluvial depos its derived from adjacent  map units.  Seasonal high water table and potent ial for frequent flood ing.    Qallt – River Channel Belt – Low Terrace (DeFo rest  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 brown, noncalcareous, st rat ified si lty clay  loam, loam, or clay loam, associated w ith the modern  channel belt of the West Nishnabotna, West  Fork West  Nishnabotna, and  Eas t Branch West Nishnabo tna river val leys.  Overlies Pre-Ho locene fine-g rained al luvium.   Occupies lowes t po sit ion on the floodp lain ie. modern and his toric channel bel ts.  Ox-bow  lakes and meander scars  are common features  associated  with th is terrace level.  Mapped primarily  using aerial imagery and coun ty soil  survey data.  Seasonal h igh water tab le and frequent flooding potent ial.     HUDSON AND WISCONSIN EPISODE  WISCONSIN EPISODE  Qpt- Loess Mantled Terrace (Peoria Fo rmation – sil t and/or sand facies) 2 to 9 m (7-30  ft) o f yellowish  brown to  gray, massive, jointed , calcareous or noncalcareous,  silt  loam and  intercalated fine to  medium, well sorted, sand . May grade downward to poo rly to moderately well sorted, moderately to w ell strati fied, coarse to fine feldspathic quartz sand, lo am, o r si lt loam al luvium (Late Phase High Terrace) or may overlie a Farmdale Geoso l developed in  Roxanna Silt  which in turn overlies a well-expressed Sangamon Geoso l developed  in poorly to moderately well  so rted , moderately to  well s tratified,  coarse to fine sand, lo am, or s ilt  loam alluvium (Early Phase High Terrace).  Qps – Loess    (Peoria Formation—silt facies)  Generally 3 to 15  m (10-50 ft ) of yel low ish to grayish brown,  mass ive, jointed calcareous or noncalcareous sil t loam to s il ty clay loam.  D eposits are thickest in the wes tern  port ion of the county and  th in to the east .  Limited areas o f fine eol ian sand may be present near major river valleys .  Overlies  a grayish brown to o live gray s ilty clay loam to sil ty clay (Pisgah Formation—eroded Farmdale Geoso l) w hich is  less than  1 .5 m (5 ft) thick.  The Farmdale may be w elded to an older Sangamon Geosol  developed  in loamy glacial ti ll o f the Wolf Creek o r Alburnet t fo rmations. This  mapping unit encompasses upland  divides,  ridgetops and convex sideslopes .  Well  to somewhat  poo rly drained  landscape.  PRE-ILLINOIS EPISODE  Qwa3 – Till  (Wolf Creek or Albu rnet t Fo rmations)   General ly 15 to 137  m (50-450 ft) o f  very dense, massive, fractured,  lo amy glacial ti ll of the Wolf Creek or A lburnett formations with  or without  a thin  loess mantle (Peoria Formation—less than 2 m) and interven ing clayey Farmdale/Sangamon Geosol . This  mapp ing unit encompasses  narrowly d issected interfluves and s ide slopes, and side val ley slopes.  Drainage is variable from w ell drained to  poo rly drained.   Other Mapping Units  Qpq - Pits and Quarries  Sand and gravel pits  and rock  quarries.  Extent mapped as shown in county so il surveys and as identified on aerial imagery.   Water Features   Rivers , lakes  and small ponds fo rmed by blockage of d rainagew ays and  river channels.  Extent  mapped  as shown in county so il surveys and  as ident ified on aerial  imagery.    Water Wells    


Surficial Geology of Shelby County, Iowa

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Surficial Geology of Shelby County, Iowa

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