White River Group

Includes: Brule Formation (Oligocene)- White, pink, light-green, and light-brown, massive to thin-bedded, bentonitic claystone, tuffaceous siltstone, and well-bedded, calcareous, tuffaceous quartz sandstone. Thickness up to 150 ft (46 m). Chadron Formation (Eocene)- Upper beds are gray, light-brown to maroon bentonite, claystone, siltstone tuffaceous fine-grained sandstone, and local, silicified carbonate lenses. Basal portion consists of poorly cemented, white, coarse-grained arkose and conglomerate. Thickness up to 160 ft (49 m). Chamberlain Pass Formation (Eocene)- Pale olive to pale red, mottled mudstone containing white, cross-bedded channel sandstone with basal conglomerate. Thickness up to 32 ft (10 m). Slim Buttes Formation (Eocene)- White, grayish- to yellowish-orange,pale-red to pink siltstone, clayey siltstone, bentonitic claystone,medium- to fine-grained sandstone, and conglomerate. Thickness up to 48 ft (15 m).
State South Dakota
Name White River Group
Geologic age Oligocene to Eocene
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed, Calcareous)
Sedimentary > Clastic > Mudstone > Claystone (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Minor
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)
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, GM 10, scale 1:500,000.

NGMDB product
Counties Butte - Custer - Fall River - Gregory - Haakon - Harding - Jackson - Jones - Lawrence - Meade - Mellette - Pennington - Perkins - Shannon - Stanley - Todd - Tripp