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Clayely Till, Ground Moraine

Heterogeneous, clay to boulder-size clasts of glacial orgin. Exhibits a distinctive weathered, dissected surface. Contains prominent oxidized joints and fractures with gypsum or calcite. Typically overlain by up to 45 ft (14 m) of loess. Thickness of uppermost Pre-Illinoian till may be up to 120 ft (37 m). Composite thickness of all Pre-Illinoian till may be up to 1,000 ft (305 m).
State South Dakota
Name Clayely Till, Ground Moraine
Geologic age Phanerozoic | Cenozoic | Quaternary | Pleistocene [Pre-Illinoian]
Primary rock type clay or mud
Secondary rock type silt
Other rock types sand; gravel
Lithologic constituents
Major
Unconsolidated > Fine-detrital > Silt (Glacial, till)
Unconsolidated > Coarse-detrital > Sand (Glacial, till)
Unconsolidated > Coarse-detrital > Gravel (Glacial, till)
Unconsolidated > Coarse-detrital > Boulders (Glacial, till)
Map references
Martin, J. E., Sawyer, J. F., Fahrenbach, M. D., Tomhave, D. W., and Schulz, L. D., 2004, Geologic Map of South Dakota: South Dakota Geological Survey
Unit references
Martin, J. E., Sawyer, J. F., Fahrenbach, M. D., Tomhave, D. W., and Schulz, L. D., 2004, Geologic Map of South Dakota: South Dakota Geological Survey
Counties Clay - Lincoln - Minnehaha - Moody - Union