Surficial Geologic Materials of Hardin County, Iowa · Qtr_amI - Till ridge (Dows Formation-Morgan...
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Quade, 1 and James D. Giglierano 1 Iowa Department of Natural Resources, Jeffrey R. Vonk, Director Iowa Geological Survey, Robert D. Libra, State Geologist Supported by the U.S. Geological Survey Cooperative Agreement Number 05HQAG0086 National Cooperative Geologic Mapping Program (STATEMAP) ACKNOWLEDGEMENTS Recognized for contributions to map’s production: Ray Anderson, Bob Libra, Andrew Asell, Pete Kollasch, Heather Buresh, Katie Foreman, Mary Pat Heitman, and Lois Bair. Drilling was provided under a contract with Aquadrill of Iowa City, Iowa; a special thanks to Jay Joslyn and drilling crew members who worked at times in challenging drilling conditions. A special thanks to the following individuals who graciously allowed access to their land for drilling, Jeff Cook, Charles Crandall, Frank Dagit, Ron Galloway, Greg Gilbert, James Ioger, James Handsaker, Keith Helvig, Mark Hobson, Lawrence and Allen Kadolph, Randy Madden, Henrietta Miller, Marvin Reifschneider, M. Schunemen and Ken Smith. Thank you to Dr. William Simpkins and graduate student Lucie Macalister of Iowa State University for their assistance in lining up drilling sites and assisting with coring. Also, we would like to recognize the efforts of the South Fork Watershed Alliance, National Tilth Laboratory, and USGS for their involvement in various hydrogeologic studies on the South Fork of the Iowa River in Hardin County. 1 Iowa Department of Natural Resources, Iowa Geological Survey 109 Trowbridge Hall, Iowa City, IA 52242-1319 Surficial Geologic Materials of Hardin County, Iowa LEGEND Description of Map Units Cenozoic Quaternary System Hudson Episode Qo - Depressions (DeForest Formation-Woden Mbr.) Generally 8 to 16.5 feet (2.5 to 6 meters) of black to very dark gray, calcareous, muck, peat and silty clay loam colluvium and organic sediments in drained and undrained closed and semi-closed depressions. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.) or Noah Creek Fm. sand and gravel. Associated with low relief features that occupy depressions and low sags on the landscape. Supports wetland vegetation and can be permanently covered by water. High water table. Qal - Alluvium (DeForest Formation-Undifferentiated) Variable thickness 3 to 16.5 feet (<1 to 5 meters) of very dark gray to brown, noncalcareous to calcareous, stratified silty clay loam, clay loam, loam to sandy loam alluvium and colluvium in stream valleys, on hill slopes and in closed depressions. May overlie Dows Formation (Morgan or Alden mbrs.), or Noah Creek Formation. Off the Des Moines Lobe this unit overlies Pre-Illinoian diamicton. Associated with low-relief modern floodplain, closed depressions, modern drainageways or toeslope positions on the landscape. Seasonal high water table and potential for frequent flooding. Wisconsin Episode Qtr_bm - Till ridge (Dows Formation-Morgan Mbr.) Generally 10 to 16.5 feet (3 to 5 meters) of yellowish to grayish brown, usually calcareous and fractured, stratified loam to silt loam; stratified sands and gravels to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit rarely extends to depths greater than 40 to 50 feet (12 to 15 meters); and overlies the Sheldon Creek Formation diamicton. At the DML margin, this landform may be mantled with a thin layer of Peoria Formation silt. Low to moderate relief hummocky landform features exceed 10 to 16.5 feet) (3 to 5 meters) of local relief. This landform is associated with the Bemis Moraine. The surface pattern is irregularly shaped patterns. Seasonal high water table. Qtr_amI - Till ridge (Dows Formation-Morgan Mbr. or Pilot Knob Mbr or Lake Mills Mbr.) Generally 29.5 to 50 feet (9 to 15 meters) of yellowish to grayish brown, usually calcareous and fractured, stratified loam to silt loam; stratified sands and gravels to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 25 meters. This sediment package may overlie the Sheldon Creek Formation or Pre_Illinoian diamicton. Moderate to high relief hummocky landform features exceed 10 to 33 feet (3 to 10 meters) of local relief. This landform is characterized by moderate to high relief hummocks, and in places esker and kame features. The surface pattern is primarily rounded irregularly shaped patterns. This landform is associated with the Altamont I Moraine. Seasonal high water table. Qtp- Till plain (Dows Formation-Morgan Mbr.) Less than 26 feet (8 meters) of yellowish brown, often calcareous and fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-- Alden Mbr.). Low to moderate relief 10 to 26 feet (3 to 8 m), undulating plains with irregular surface patterns. Seasonal high water table. Qtpl1 - Aligned ridge to discontinuous elongated hummocky ridge forms (Dows Formation--Morgan Mbr./ Pilot Knob Mbr.) Less than 26 feet (8 meters) of yellowish brown, calcareous, fractured, stratified sand and gravel with interbedded stratified loam diamicton or yellowish to grayish brown, calcareous, fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 15 to 20 meters and may overlie Sheldon Creek Formation or Pre-Illinoian diamicton. Low to moderate relief, less than 26 feet (8 meters) of local relief, slightly undulating plains with irregular surface patterns. Aligned ridges to discontinuous elongated ridge forms within the unit are underlain by less than 26 feet (8 meters) of yellowish brown, often calcareous, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Evidence of shearing is sometimes present. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). Tracts of faint to distinct aligned ridges to elongated hummocks oriented transverse to glacier flow on the till plain with irregular shaped surface patterns. Ridges or aligned hummocks are low to moderate relief features 10 to 26 feet (3 to 8+ meters) Overall landform exhibits swell and swale topography. Seasonal high water table. Qtpld4 - Till Plain with linked depression systems and discontinuous elongated hummocky ridge forms (Dows Formation—Morgan Mbr./Pilot Knob Mbr.) Less than 26 feet (8 meters) of yellowish brown, calcareous, fractured, stratified sand and gravel with interbedded stratified loam diamicton or yellowish to grayish brown, calcareous, fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.- Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 50 to 65.5 feet (15 to 20 meters) and may overlie Sheldon Creek Formation or Pre-Illinoian diamicton. Discontinuous elongated ridge forms within the unit are underlain by less than 26 feet (8 meters) of yellowish brown, often calcareous, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). Indistinct elongated hummocks are oriented transverse to glacier flow on a very low relief till plain with reticulate linked-depression systems. Ridge forms are predominately low relief <10 feet (<3 meters) features. Low to moderate relief 10 to 26 feet (3 to 8 meters) discontinuous isolated ridges that run oblique to glacier flow are common. Numerous medium to large depressions and small glacial and historic lake beds. Overall landform exhibits swell and swale topography. High water table. Qtpld4-3 - Till plain with linked depression systems and aligned ridge forms to discontinuous elongated hummocky ridge forms (Dows Formation—Morgan Mbr./Pilot Knob Mbr.) Less than 26 feet (8 meters) of yellowish brown, calcareous, fractured, stratified sand and gravel with interbedded stratified loam diamicton or yellowish to grayish brown, calcareous, fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 50 to 65.5 feet (15 to 20 meters) and may overlie Sheldon Creek Formation or Pre- Illinoian diamicton. Aligned ridges to discontinuous elongated ridge forms. These are overlain by less than 26 meters (8 meters) of yellowish brown, often calcareous, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Evidence of shearing is sometimes present. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr. Tracts of faint to distinct aligned ridges to elongated hummocks oriented transverse to glacier flow on a very low relief till plain with reticulate linked-depression systems. Ridges or aligned hummocks are low to moderate relief features 10 to 26+ feet (3 to 8+ meters). Low to moderate relief 10 to 26 feet (3 to 8 meters) discontinuous isolated ridges that run oblique to glacier flow are not uncommon. Numerous medium to large depressions and small glacial and lake beds. Overall landform exhibits swell and swale topography. High water table. Qoch - Valley train outwash (Noah Creek Formation) Generally 26 to 50 feet (8 to 15 meters) of dark gray, dark grayish brown, dark brown to dark yellowish brown medium to coarse sand, gravelly sand to pebbly gravel. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). In valley positions, it is at the land surface of older terraces. On the modern floodplain it is buried by DeForest Fm. alluvium. Low-relief landforms expressed as broad terraces; long, narrow longitudinal terraces or cuspate-shaped point terraces. Terraces associated with the major valleys are benched on a gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). This unit encompasses deposits that accumulated in stream valleys during the Wisconsin Episode. No flooding potential, unless buried by DeForest Fm. on the modern floodplain. Qnw – Sand and Gravel (Noah Creek Formation) More than 10 feet (3 meters) of yellowish brown to gray, poorly to well sorted, massive to well stratified, coarse to fine feldspathic quartz sand, pebbly sand and gravel. In places mantled with one to three meters of fine to medium, well sand derived from wind reworking of the alluvium. This unit encompasses deposits that accumulated in stream valleys during the Wisconsin Episode. Qps – Loess (Peoria Formation—silt facies) Generally 6.5ft to 13 ft (2 to 4 m) of yellowish to grayish brown, massive, jointed calcareous or noncalcareous silt loam to silty clay loam. Overlies a grayish brown to olive gray silty clay loam to silty clay (Pisgah Formation—eroded Farmdale Geosol) which is less than 5 feet (1.5 meters) thick. The Farmdale Geosol appears to be disturbed by periglacial action and is welded to an older Sangamon Geosol developed in loess. This mapping unit encompasses upland divides, ridgetops and convex sideslopes. Well to somewhat poorly drained landscape. Qe - Sand Dunes and Sand Sheets (Peoria Formation-sand facies) Generally less than 10 feet (3 meters) of yellowish brown, massive, calcareous loamy sand to fine sand. It may overlie yellowish-brown coarse-grained sand and gravel (Noah Creek Fm.), or it may overlie yellowish to grayish brown, usually calcareous, stratified loam to silt loam to sandy loam diamicton (Dows Fm.-Morgan Mbr.). Usually restricted to a narrow belt along major river valley bottoms or adjacent uplands on the Des Moines Lobe. Off the Des Moines Lobe this unit is not restricted to dunes along valley areas and may occur as sand stringers overlying unnamed erosion surface loamy sediments. Qwa2 - Loamy and Sandy Sediment Shallow to Glacial Till (Unnamed erosion surface sediment ) Three to ten feet (1 to 3 meters) of yellowish brown to gray, massive to weakly stratified, well to poorly sorted loamy, sandy and silty erosion surface sediment. Map unit includes some areas mantled with less than 13 ft (2 m) of Peoria Silt (loess). Overlies massive, fractured, firm Pre-Illinoian diamicton. Seasonally high water table may occur in this map unit. Paleozoic Mu - Mississippian Bedrock Exposures (Gilmore City, Maynes Creek and Prospect Hill formations) Lower Mississippian--Composed of marine limestone, dolomite, cherty dolomite; possibly some shale. Exposures present along the Iowa River valley from Alden through Eagle City area. Pu - Pennsylvanian Bedrock Exposures (Cherokee Group) Middle Pennsylvanian-- Primarily composed of deltaic sediments associated with the Cherokee Group. Lithologies are extremely variable. Major lithologies consist of shale and sandstone with minor coal seams. Exposed along the Iowa River valley downstream from Steamboat Rock. Bedrock within 25 feet (7.6 meters) of land surface. Qf - Fill Areas of major land filling. Fill associated with railroad grades, highway grades and land leveling. Variable in texture ranging from loamy to sandy to concrete rubble. Extent mapped as shown in county soil surveys. Qpq - Pits and Quarries Sand and gravel pits and rock quarries. Extent mapped as shown in county soil surveys. Water Features Drill Holes ± 0 5 10 15 20 2.5 Miles Scale 1:100,000 0 5 10 15 20 2.5 Kilometers Location Diagram Des Moines Lobe Region Hardin WRIGHT FRANKLIN BUTLER HAMILTON HARDIN GRUNDY STOR Y MARSHALL Adjacent Iowa Counties Alta m ont I M ora i ne Shaded Relief Map of Hardin County Base map components from the Iowa DNR Natural Resource GIS Library (NRGIS) 100,000 scale Hardin County GIS files: PLSS42.shp and Rivers42.shp Iowa statewide GIS files: Incorp.shp, Highway.shp and Township.shp Shaded relief map derived from US Geological Survey 30 meter National Elevation Dataset (NRGIS file \NED\hillshade) Iowa Geological Survey digital cartographic file HardinCo06.mxd, version 6/29/06 (ArcGIS 9.0) Map projection and coordinate system based on Universal Transverse Mercator (UTM) Zone 15, datum NAD83 Bemi s Mo r ain e 0 2 4 6 8 1 Miles
Transcript of Surficial Geologic Materials of Hardin County, Iowa · Qtr_amI - Till ridge (Dows Formation-Morgan...
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SURFICIAL GEOLOGIC MAP OF THE DES MOINES LOBE OF IOWA
Phase 8: Hardin County
Iowa Geological Survey Open File Map OFM-06-6
July 2006
Prepared by
Deborah J. Quade, 1and James D. Giglierano1
Iowa Department of Natural Resources, Jeffrey R. Vonk, Director Iowa Geological Survey, Robert D. Libra, State Geologist
Supported by the U.S. Geological Survey Cooperative Agreement Number 05HQAG0086
National Cooperative Geologic Mapping Program (STATEMAP)
ACKNOWLEDGEMENTS
Recognized for contributions to map’s production: Ray Anderson, Bob Libra, Andrew Asell, Pete Kollasch, Heather Buresh, Katie Foreman, Mary Pat Heitman, and Lois Bair. Drilling was provided under a contract with Aquadrill of Iowa City, Iowa; a special thanks to Jay Joslyn and drilling crew members who worked at times in challenging drilling conditions. A special thanks to the following individuals who graciously allowed access to their land for drilling, Jeff Cook, Charles Crandall, Frank Dagit, Ron Galloway, Greg Gilbert, James Ioger, James Handsaker, Keith Helvig, Mark Hobson, Lawrence and Allen Kadolph, Randy Madden, Henrietta Miller, Marvin Reifschneider, M. Schunemen and Ken Smith. Thank you to Dr. William Simpkins and graduate student Lucie Macalister of Iowa State University for their assistance in lining up drilling sites and assisting with coring. Also, we would like to recognize the efforts of the South Fork Watershed Alliance, National Tilth Laboratory, and USGS for their involvement in various hydrogeologic studies on the South Fork of the Iowa River in Hardin County. 1Iowa Department of Natural Resources, Iowa Geological Survey 109 Trowbridge Hall, Iowa City, IA 52242-1319
Surficial Geologic Materials of Hardin County, IowaLEGEND
Description of Map Units
Cenozoic
Quaternary System
Hudson Episode
Qo - Depressions (DeForest Formation-Woden Mbr.) Generally 8 to 16.5 feet (2.5 to 6 meters) of black to very dark gray, calcareous, muck, peat and silty clay loam colluvium and organic sediments in drained and undrained closed and semi-closed depressions. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.) or Noah Creek Fm. sand and gravel. Associated with low relief features that occupy depressions and low sags on the landscape. Supports wetland vegetation and can be permanently covered by water. High water table. Qal - Alluvium (DeForest Formation-Undifferentiated) Variable thickness 3 to 16.5 feet (<1 to 5 meters) of very dark gray to brown, noncalcareous to calcareous, stratified silty clay loam, clay loam, loam to sandy loam alluvium and colluvium in stream valleys, on hill slopes and in closed depressions. May overlie Dows Formation (Morgan or Alden mbrs.), or Noah Creek Formation. Off the Des Moines Lobe this unit overlies Pre-Illinoian diamicton. Associated with low-relief modern floodplain, closed depressions, modern drainageways or toeslope positions on the landscape. Seasonal high water table and potential for frequent flooding.
Wisconsin Episode Qtr_bm - Till ridge (Dows Formation-Morgan Mbr.) Generally 10 to 16.5 feet (3 to 5 meters) of yellowish to grayish brown, usually calcareous and fractured, stratified loam to silt loam; stratified sands and gravels to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit rarely extends to depths greater than 40 to 50 feet (12 to 15 meters); and overlies the Sheldon Creek Formation diamicton. At the DML margin, this landform may be mantled with a thin layer of Peoria Formation silt. Low to moderate relief hummocky landform features exceed 10 to 16.5 feet) (3 to 5 meters) of local relief. This landform is associated with the Bemis Moraine. The surface pattern is irregularly shaped patterns. Seasonal high water table. Qtr_amI - Till ridge (Dows Formation-Morgan Mbr. or Pilot Knob Mbr or Lake Mills Mbr.) Generally 29.5 to 50 feet (9 to 15 meters) of yellowish to grayish brown, usually calcareous and fractured, stratified loam to silt loam; stratified sands and gravels to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 25 meters. This sediment package may overlie the Sheldon Creek Formation or Pre_Illinoian diamicton. Moderate to high relief hummocky landform features exceed 10 to 33 feet (3 to 10 meters) of local relief. This landform is characterized by moderate to high relief hummocks, and in places esker and kame features. The surface pattern is primarily rounded irregularly shaped patterns. This landform is associated with the Altamont I Moraine. Seasonal high water table. Qtp- Till plain (Dows Formation-Morgan Mbr.) Less than 26 feet (8 meters) of yellowish brown, often calcareous and fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-- Alden Mbr.). Low to moderate relief 10 to 26 feet (3 to 8 m), undulating plains with irregular surface patterns. Seasonal high water table. Qtpl1 - Aligned ridge to discontinuous elongated hummocky ridge forms (Dows Formation--Morgan Mbr./ Pilot Knob Mbr.) Less than 26 feet (8 meters) of yellowish brown, calcareous, fractured, stratified sand and gravel with interbedded stratified loam diamicton or yellowish to grayish brown, calcareous, fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 15 to 20 meters and may overlie Sheldon Creek Formation or Pre-Illinoian diamicton. Low to moderate relief, less than 26 feet (8 meters) of local relief, slightly undulating plains with irregular surface patterns. Aligned ridges to discontinuous elongated ridge forms within the unit are underlain by less than 26 feet (8 meters) of yellowish brown, often calcareous, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Evidence of shearing is sometimes present. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). Tracts of faint to distinct aligned ridges to elongated hummocks oriented transverse to glacier flow on the till plain with irregular shaped surface patterns. Ridges or aligned hummocks are low to moderate relief features 10 to 26 feet (3 to 8+ meters) Overall landform exhibits swell and swale topography. Seasonal high water table. Qtpld4 - Till Plain with linked depression systems and discontinuous elongated hummocky ridge forms (Dows Formation—Morgan Mbr./Pilot Knob Mbr.) Less than 26 feet (8 meters) of yellowish brown, calcareous, fractured, stratified sand and gravel with interbedded stratified loam diamicton or yellowish to grayish brown, calcareous, fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.- Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 50 to 65.5 feet (15 to 20 meters) and may overlie Sheldon Creek Formation or Pre-Illinoian diamicton. Discontinuous elongated ridge forms within the unit are underlain by less than 26 feet (8 meters) of yellowish brown, often calcareous, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). Indistinct elongated hummocks are oriented transverse to glacier flow on a very low relief till plain with reticulate linked-depression systems. Ridge forms are predominately low relief <10 feet (<3 meters) features. Low to moderate relief 10 to 26 feet (3 to 8 meters) discontinuous isolated ridges that run oblique to glacier flow are common. Numerous medium to large depressions and small glacial and historic lake beds. Overall landform exhibits swell and swale topography. High water table. Qtpld4-3 - Till plain with linked depression systems and aligned ridge forms to discontinuous elongated hummocky ridge forms (Dows Formation—Morgan Mbr./Pilot Knob Mbr.) Less than 26 feet (8 meters) of yellowish brown, calcareous, fractured, stratified sand and gravel with interbedded stratified loam diamicton or yellowish to grayish brown, calcareous, fractured, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). The Alden Mbr. in this mapping unit can extend to depths in excess of 50 to 65.5 feet (15 to 20 meters) and may overlie Sheldon Creek Formation or Pre-Illinoian diamicton. Aligned ridges to discontinuous elongated ridge forms. These are overlain by less than 26 meters (8 meters) of yellowish brown, often calcareous, stratified loam to silt loam to sandy loam diamicton; textures can be quite variable. Evidence of shearing is sometimes present. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr. Tracts of faint to distinct aligned ridges to elongated hummocks oriented transverse to glacier flow on a very low relief till plain with reticulate linked-depression systems. Ridges or aligned hummocks are low to moderate relief features 10 to 26+ feet (3 to 8+ meters). Low to moderate relief 10 to 26 feet (3 to 8 meters) discontinuous isolated ridges that run oblique to glacier flow are not uncommon. Numerous medium to large depressions and small glacial and lake beds. Overall landform exhibits swell and swale topography. High water table. Qoch - Valley train outwash (Noah Creek Formation) Generally 26 to 50 feet (8 to 15 meters) of dark gray, dark grayish brown, dark brown to dark yellowish brown medium to coarse sand, gravelly sand to pebbly gravel. Overlies gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). In valley positions, it is at the land surface of older terraces. On the modern floodplain it is buried by DeForest Fm. alluvium. Low-relief landforms expressed as broad terraces; long, narrow longitudinal terraces or cuspate-shaped point terraces. Terraces associated with the major valleys are benched on a gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). This unit encompasses deposits that accumulated in stream valleys during the Wisconsin Episode. No flooding potential, unless buried by DeForest Fm. on the modern floodplain. Qnw – Sand and Gravel (Noah Creek Formation) More than 10 feet (3 meters) of yellowish brown to gray, poorly to well sorted, massive to well stratified, coarse to fine feldspathic quartz sand, pebbly sand and gravel. In places mantled with one to three meters of fine to medium, well sand derived from wind reworking of the alluvium. This unit encompasses deposits that accumulated in stream valleys during the Wisconsin Episode. Qps – Loess (Peoria Formation—silt facies) Generally 6.5ft to 13 ft (2 to 4 m) of yellowish to grayish brown, massive, jointed calcareous or noncalcareous silt loam to silty clay loam. Overlies a grayish brown to olive gray silty clay loam to silty clay (Pisgah Formation—eroded Farmdale Geosol) which is less than 5 feet (1.5 meters) thick. The Farmdale Geosol appears to be disturbed by periglacial action and is welded to an older Sangamon Geosol developed in loess. This mapping unit encompasses upland divides, ridgetops and convex sideslopes. Well to somewhat poorly drained landscape. Qe - Sand Dunes and Sand Sheets (Peoria Formation-sand facies) Generally less than 10 feet (3 meters) of yellowish brown, massive, calcareous loamy sand to fine sand. It may overlie yellowish-brown coarse-grained sand and gravel (Noah Creek Fm.), or it may overlie yellowish to grayish brown, usually calcareous, stratified loam to silt loam to sandy loam diamicton (Dows Fm.-Morgan Mbr.). Usually restricted to a narrow belt along major river valley bottoms or adjacent uplands on the Des Moines Lobe. Off the Des Moines Lobe this unit is not restricted to dunes along valley areas and may occur as sand stringers overlying unnamed erosion surface loamy sediments. Qwa2 - Loamy and Sandy Sediment Shallow to Glacial Till (Unnamed erosion surface sediment ) Three to ten feet (1 to 3 meters) of yellowish brown to gray, massive to weakly stratified, well to poorly sorted loamy, sandy and silty erosion surface sediment. Map unit includes some areas mantled with less than 13 ft (2 m) of Peoria Silt (loess). Overlies massive, fractured, firm Pre-Illinoian diamicton. Seasonally high water table may occur in this map unit.
Paleozoic Mu - Mississippian Bedrock Exposures (Gilmore City, Maynes Creek and Prospect Hill formations) Lower Mississippian--Composed of marine limestone, dolomite, cherty dolomite; possibly some shale. Exposures present along the Iowa River valley from Alden through Eagle City area. Pu - Pennsylvanian Bedrock Exposures (Cherokee Group) Middle Pennsylvanian-- Primarily composed of deltaic sediments associated with the Cherokee Group. Lithologies are extremely variable. Major lithologies consist of shale and sandstone with minor coal seams. Exposed along the Iowa River valley downstream from Steamboat Rock. Bedrock within 25 feet (7.6 meters) of land surface. Qf - Fill Areas of major land filling. Fill associated with railroad grades, highway grades and land leveling. Variable in texture ranging from loamy to sandy to concrete rubble. Extent mapped as shown in county soil surveys. Qpq - Pits and Quarries Sand and gravel pits and rock quarries. Extent mapped as shown in county soil surveys. Water Features Drill Holes
± 0 5 10 15 202.5Miles
Scale 1:100,000
0 5 10 15 202.5Kilometers
Location Diagram
Des MoinesLobe
Region
HardinWRIGHT
FRANKLIN
BUTLER
HAMILTON
HARDIN
GRUNDY
STORY
MARSHALL
Adjacent Iowa Counties
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Shaded Relief Map of Hardin County
Base map components from the Iowa DNR Natural Resource GIS Library (NRGIS)100,000 scale Hardin County GIS files: PLSS42.shp and Rivers42.shp Iowa statewide GIS files: Incorp.shp, Highway.shp and Township.shp
Shaded relief map derived from US Geological Survey 30 meter National Elevation Dataset (NRGIS file \NED\hillshade)
Iowa Geological Survey digital cartographic file HardinCo06.mxd, version 6/29/06 (ArcGIS 9.0)Map projection and coordinate system based on Universal Transverse Mercator (UTM) Zone 15, datum NAD83
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