Cretaceous, undifferentiated

Black opaline spiculite, gray to black shale, yellow-brown to gray chalk, gray silty clay, and pink quartz-rich sandstone. Includes the Split Rock Creek Formation and other near-shore facies of the Dakota Formation, Graneros Shale, Greenhorn Formation, Carlile Shale, Niobrara Formation, and Pierre Shale. Thickness up to 400 ft (122 m).
State South Dakota
Name Cretaceous, undifferentiated
Geologic age Upper to Lower Cretaceous
Lithologic constituents
Sedimentary > Clastic > Mudstone > Shale (Bed)Gray to black shale
Sedimentary > Chemical > Chert (Bed)Black opaline spiculite.
Sedimentary > Carbonate > Limestone > Chalk (Bed)Yellow-brown to gray chalk
Unconsolidated > Fine-detritalGray silty clay
Sedimentary > Clastic > Sandstone (Bed)Pink quartz-rich sandstone

Tomhave, D.W., and Schulz, L.D., 2004, Bedrock Geologic Map Showing Configuration of the Bedrock Surface in South Dakota East of the Missouri River, South Dakota Geological Survey, GM 9, scale 1:500,000.

NGMDB product
Counties Brookings - Hutchinson - Lake - Lincoln - McCook - Minnehaha - Moody - Turner