Arikaree Formation

Greenish gray, fine-grained sandstone with interbedded light gray volcanic ash. Nonmarine to possibly marine-influenced. Thickness as much as 80 m (262 ft). Incudes White River Group - Brule Formation: Pink, sandy, locally bentonitic claystone with siliceous concretions. Nonmarine. Preserved in local areas below Arikaree Formation. Thickness as much as 10 m (33 ft). Chadron Formation: Very light gray, fine-grained sandstone. Nonmarine. Preserved locally with Brule Formation. Thickness as much as 30 m (98 ft).
State Montana
Name Arikaree Formation
Geologic age Tertiary
Lithologic constituents
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)
Sedimentary > Clastic > Sandstone (Bed)
Igneous > Volcanic (Pyroclastic)volcanic ash

Vuke, S.M., Porter, K.W., Lonn, J.D., and Lopez, D.A., 2007, Geologic Map of Montana - Compact Disc: Montana Bureau of Mines and Geology: Geologic Map 62-C, 73 p., 2 sheets, scale 1:500,000. This map was digitized in 2012 as a result of a contract between the U.S. Geological Survey and the Montana Bureau of Mines and Geology.

NGMDB product
Counties Carter