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Surficial Geologic Materials of Polk County, Iowa
LEGEND
Description of Mapping Units
Hudson Episode Qo - Depressions (DeForest Formation-Woden Mbr.) Generally 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 less than 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 hillslopes and in closed depressions. May overlie Dows Formation (Morgan or Alden Mbrs.), Noah Creek Formation, or Pennsylvanian bedrock. Associated with low-relief modern floodplain, closed depressions, modern drainageways or toe slope positions on the landscape. Seasonal high water table and potential for frequent flooding. Qallt - Raccoon River, Des Moines River, Skunk River and Beaver Creek Valley - Low Terrace (DeForest Formation-Camp Creek Mbr. and Roberts Creek Mbr.). Variable thickness of less than 1 to 5 meters of very dark gray to brown, noncalcareous, stratified silty clay loam, loam, or clay loam, associated with the modern channel belt of the Des Moines, Raccoon, Skunk and Beaver Creek valleys. Overlies Noah Creek Formation. Occupies lowest position on the floodplain ie. modern channel belts. Seasonal high water table and frequent flooding potential. Qalit - Raccoon River, Des Moines River, Skunk River and Beaver Creek Valley - Intermediate Terrace (DeForest Formation-Camp Creek Mbr., Roberts Mbr. and Gunder Mbr.) Variable thickness of less than 1 to 5 meters of very dark gray to brown, noncalcareous, stratified silty clay loam to loam that overlies Noah Creek Formation. Occupies low terrace position. Seasonal high water table and frequent flooding potential. Qali-ht - Raccoon River, Des Moines River, Skunk River and Beaver Creek Valley � Intermediate-High Terrace (DeForest Formation-Gunder Mbr.) Variable thickness of less than 1 to 5 meters of very dark gray to brown, noncalcareous, silty clay loam to loam alluvium or colluvium that overlies Noah Creek Formation. Occupies terrace and valley margin position 1 to 2 meters above the modern floodplain. Seasonal high water table and low to moderate flooding potential. Qalht - Raccoon River, Des Moines River, Skunk River and Beaver Creek Valley - High Terrace (DeForest Formation-Gunder and Corrington Mbrs.) Variable thickness of less than 1 to 7 meters of very dark gray to brown, noncalcareous, silty clay loam, loam alluvium or colluvium. Overlies Noah Creek Formation. Occupies terrace and valley margin position 2 to 3 meters above the modern floodplain, steep-angled fans at the base of low order drainages, and colluvial slopes along the margin of major river valleys. Seasonal high water table and rare flooding potential.
Wisconsin Episode Qe - Sand Dunes and Sand Sheets (Peoria Formation-sand facies) Generally less than 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 and adjacent uplands on the Des Moines Lobe. Qps1 - Loess (Peoria Formation-silt facies) Generally 2 to 4 meters of yellowish to grayish brown, massive, jointed, calcareous or noncalcareous silt loam to silty clay loam. East of the Des Moines River there is a localized, narrow band of 9 to 11 meters of thick loess that thins to the eastern boundary of the county. The loess overlies a grayish brown to olive gray silty clay loam to silty clay (Pisgah Formation-eroded Farmdale Geosol) which is less than 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 or Pre-Illinoian till (Wolf Creek or Alburnett Formations). This mapping unit encompasses upland divides, ridge tops and convex side slopes. Well to somewhat poorly drained landscape. Qtpl - Till Plain with discontinuous elongated hummocky ridge forms (Dows Formation-Morgan Mbr.) Less than 4 meters of 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 area is thinner and extends to depths of only 8 to 15 meters, and overlies Peoria Formation-silt facies, Pisgah Formation�Farmdale Geosol or Pre-Illinoian diamicton. Low relief, (less than 3 meters of local relief), slightly undulating plains with irregular surface patterns. Discontinuous elongated ridge forms within the unit are underlain by less than 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 the till plain with irregular shaped surface patterns. Ridges are predominately low relief (less than 3 meters) with some moderate relief features (3 to 8 meters). Overall landform exhibits swell and swale topography. Seasonal high water table. Qtpl1 - Aligned ridge to discontinuous elongated hummocky ridge forms (Dows Formation--Morgan Mbr./Pilot Knob Mbr.) Less than 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. In depressions and sags on upland surfaces, DeForest Fm.-Woden Mbr may bury the sand and gravel. 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 30 meters and may overlie Peoria Formation-silt facies, Pisgah Formation�Farmdale Geosol or Pre-Illinoian diamicton. Low to moderate relief, (less than 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 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. In an area east of Big Creek and west of Four Mile Creek, a number of these elongated hummocks consist primarily of sand and gravel and exhibit evidence of syndepositional collapse (Pilot Knob Mbr.). Tracts of faint to distinct aligned ridges to elongated hummocks oriented transverse to glacier flow are prevalent across the till plain. Ridges or aligned hummocks are low to moderate relief features (3 to 8+ meters). Overall landform exhibits swell and swale topography. Seasonal high water table. Qtr - Till ridge (Dows Formation-Pilot Knob Mbr./ Morgan Mbr.) Generally 3 to 5 meters of yellowish to grayish brown, usually calcareous and fractured, stratified loam to silt loam; stratified sand and gravel 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 meters and may overlie Peoria Formation-silt facies, Pisgah Formation - Farmdale Geosol or Pre-Illinoian diamicton. Moderate to high relief hummocky landform features exceed 3 to 8 meters of local relief. This landform is associated with the Bemis Moraine in Polk County. Seasonal high water table. Qoch - Valley train outwash (Noah Creek Formation) Generally 3 to 15 meters of yellowish brown coarse-grained sand and 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. Outwash terraces associated with the major valleys are predominately benched on gray, calcareous, massive, dense loam diamicton (Dows Fm.-Alden Mbr.). A few are benched on Pennsylvanian bedrock. In upland positions it is associated with higher relief elongated hummocks (3 to 8+ meters) consisting of primarily sand and gravel and exhibiting evidence of syndepositional collapse (Pilot Knob Mbr.) No flooding potential.
Pre-Illinois Episode Qwa3 - Till (Wolf Creek or Alburnett Formations) Generally 10 to 35 meters of very dense, massive, fractured, loamy glacial till of the Wolf Creek or Alburnett Formations with or without a thin loess mantle (Peoria Formation - less than 2 meters) and intervening clayey Farmdale/Sangamon Geosol. This mapping unit encompasses narrowly dissected interfluves and side slopes, and side valley slopes. Drainage is variable from well drained to poorly drained.
Paleozoic Pu - Pennsylvanian Bedrock Exposures (Cherokee, Marmaton and Bronson Groups) Upper to Middle Pennsylvanian--Primarily light to dark gray shale, fossiliferous limestone, light gray to red mudstone and very fine to medium sandstone. Qpq - Pits and Quarries Sand and gravel pits and rock quarries. Extent mapped as shown in county soil surveys. 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. Water Features Drill Hole Locations
SURFICIAL GEOLOGIC MAP
OF THE DES MOINES LOBE OF IOWA Phase 5: Polk County
Iowa Geological Survey Open File Map 2003-3
September 2003
Prepared by Deborah J. Quade, 1James D. Giglierano1, E. Arthur Bettis III2 and Joe A. Artz3
Environmental Services Division Iowa Geological Survey and Land Quality Bureau
Supported by the U.S. Geological Survey Cooperative Agreement Number 02HQAG0034
National Cooperative Geologic Mapping Program (STATEMAP)
Iowa Department of Natural Resources Jeffrey R. Vonk, Director
ACKNOWLEDGEMENTS
Recognized for direct contributions to map�s production: Andrew B.Asell, Mary Pat Heitman, Lois Bair, and Mary Skopec,. Drilling was provided under contract by Aquadrill of Iowa City; a special thanks to Diane Joslyn, Jay Joslyn and drilling crew members who worked at times in challenging drilling conditions. Assistance in describing solum cores was provided by the Natural Resources Conservation Service, Storm Lake Office personnel, Robin Wisner. A special thanks to the following individuals who graciously allowed access to their land for drilling, Ira Cory, Basil Dawson, Betty Enfield, Ben Ferrier, Darrell Geisler, Mike Howard, Lowell Huggins, Fred and Roger Link, Harley Moore, Don Newby, Harold Silver, Darrell Snider, Walter Stewart, Nick Volz, and the staff of the Polk County Conservation Board and the Department of Natural Resources for allowing access on public lands. 1Iowa Department of Natural Resources, Iowa Geological Survey 109 Trowbridge Hall, Iowa City, IA 52242-1319 2 Department of Geoscience, The University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242 3 Office of State Archaeologist, The University of Iowa, Iowa City, IA 52242
415
415
415
316
46
950
945
931
65
65
65
65
80
235 235
80
35
35
80
163163
6
69
69
69
44
141
17
28
28
55
T81
NT
80N
T79
N
T78
N
T79N
T78N
T80N
T81N
R25W R24W R23W R22W
R22W
R23W
T77
N
R25W R24W
Des Moines
Ankeny
Johnston
Urbandale
West Des Moines
Grimes
Clive
Altoona
Bondurant
Pleasant Hill
Polk City
Alleman
Carlisle
Elkhart
Mitchellville
WindsorHeights
Sheldahl
Runnells
34 15 22 1 6345
6
6
6
26
6 32
1
31 4
3
23
16
524
6
2
4
4
1
6
5
5
1
5
15 25 4
3
3
6
4
25
7
31346
64 13
4
7
5
77
4
7
25
7
25 1 3 2 1
7
7
7
9
7
6
9
9
8
79
9
8
78
8
98
8
9
8 9 8
8 9
9
9
9
9
8
8
9
6
8
7
8
8
8
9
97
8
1513
7
2 3544 2 1 36 4
6
1
1 5 3 2 25 4
7
3 24
30
18
31
30
19
18
30
31
19
30
19
30
31
30
31
19
18
10
31
18
31
19
33
18
30
30
18
19
19
31
31
19
31
15
28
15
31
10
32
30
15
29
16
25
21
18
29
19
36
34
26
3236
18
1210
32
15
30
30
13
12
24
26
20
19
35
16
35
14
1617
22
10
21
11
20
10
32
35
28
23
2223
11
2925
28
2527
13
33
27
36
36
22
27
29
34
25
33
19
29
26
16
34
34
20
21
36
21
21
33
23
34
22
18
17
22
13
12
34
20
17
18
14
21
13
31
10
15
24
22
35
35
10
25
19
21
27
27
23
18
33
15
13
30
18
15
33
28
21
10
20
12
33
25
31
13
12
2424 22
32
11
27
34
28
26
33
24
29
13
22
22
28
34
11
30
35
15
23
28
11
3335
17
20
22
27
11
35
28
25
15
14
14
24
12
31
26
16
26
36
27
28
22
15
13
31
11
16
29
32
17
11
17
24
14
14
35
35 36
10
28
32
26
25
32
32
19
18
36
25 28
12
33
1614
29
16
26
25
27
26
16
13
14
24
20
16
16
36
10
20
29
35
14
21
27
24
23
17
10
13
27
34
17
35
31
22
25 29
33
12
14
23
29
25
34
17
26
13
26
20
22
25
11
14
30
10
24
12
24
3335
20
1513
33
21
1717
23
15
24
12
36
32
12
34
11
28
17
20
33
16
15
29
32
21
16
2024
24
11
36
36
34
27
22
22
21
21
23
25
12
14
10
23
17
33
28
27
32 35
23
12
32
27
11
14
14
27
34
11
20
27
32
24
34
24
23
17
26
26
20
13
20
12
36
10
21
15
28
23
13
14
29
20
15
26
36
36
32
23
2123
12
26
28
10
2829
14
11
16
36
22
17
21 23
16
1513
34
25
17
11
12
29
16
29
34
18
10
33
26
25
13
35
35
18
19
19
11
30
5
31
19
30
18
32
9 12
6
11109
Des Moines LobeLandform Region
Location of Mapped Area
LINN
LEE
SAC
TAMA
IDA
SIOUX
POLK IOWA
CLAY
LYON
CASS
KOSSUTH
PAGE
JASPER
ADAIR
JONESBENTON
CLAYTON
DAVIS
STORY
CEDAR
FAYETTE
CLINTONBOONE
PLYMOUTH
MONONA
DALLAS
MILLS
FLOYD
SHELBY
OBRIEN
HARDIN
BUTLER
WOODBURY WEBSTER
WAYNE
WRIGHT
MARION KEOKUK
SCOTT
JACKSON
GREENE
TAYLOR
HARRISON
UNION
GUTHRIE
LUCAS
WARREN
JOHNSON
HENRY
DUBUQUE
CRAWFORD CARROLL
MADISON
ADAMS
FRANKLIN
MAHASKA
CALHOUNGRUNDY
HANCOCK
LOUISA
HAMILTON
EMMET
POTTAWATTAMIE
ALLAMAKEE
DECATUR
WINNESHIEK
CLARKE
WORTH
MARSHALL
FREMONT
HOWARD
DELAWARE
CHEROKEE BREMER
PALO ALTO
BUCHANAN
RINGGOLD
POWESHIEK
MONROE
MITCHELL
WAPELLO
AUDUBON
BUENA VISTA
BLACK HAWK
VAN BUREN
CHICKASAW
WASHINGTON
POCAHONTAS
OSCEOLA
APPANOOSE
HUMBOLDT
MUSCATINE
CERRO GORDO
JEFFERSON
DICKINSON
DES MOINES
WINNEBAGO
MONTGOMERY
0 5 10 152.5Kilometers
0 5 10 152.5Miles
1:100,000