Niobrara Formation

White to dark-gray argillaceous chalk, marl, and shale. Weathers yellow to orange. Contains thin, laterally continuous bentonite beds, chalky carbonaceous shale, minor sand, and small concretions. Thickness up to 150 ft (46 m).
State South Dakota
Name Niobrara Formation
Geologic age Upper Cretaceous
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone > Chalk (Bed)White to dark-gray argillaceous chalk, marl, and shale.
Sedimentary > Carbonate > Marlstone (Bed)White to dark-gray argillaceous chalk, marl, and shale.
Sedimentary > Clastic > Mudstone > Shale (Bed, Carbonaceous)White to dark-gray argillaceous chalk, marl, and shale; chalky carbonaceous shale.
Minor
Unconsolidated > Coarse-detrital > Sand (Bed)
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)Contains thin, laterally continuous bentonite beds.
References

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 Aurora - Beadle - Bon Homme - Brookings - Brown - Brule - Buffalo - Butte - Charles Mix - Clay - Codington - Corson - Custer - Davison - Day - Deuel - Douglas - Edmunds - Fall River - Faulk - Grant - Gregory - Hand - Hanson - Hutchinson - Jerauld - Kingsbury - Lake - Lincoln - McCook - Marshall - Meade - Miner - Moody - Pennington - Roberts - Sanborn - Shannon - Spink - Turner - Union - Yankton