Wasatch Formation

Southeastern Montana: orangish brown, arkosic sandstone, lenticular conglomerate and siltstone, dark gray carbonaceous shale, coal, and varicolored claystone. Bears Paw Mountains: variegated red, pink, lavender, light green, yellow, gray, and very light gray shale, bentonitic claystone, and siltstone; light gray, brown, and green cross-bedded sandstone; and lenses of boulder conglomerate. Syntectonic alluvial fan and alluvial plain. Thickness as much as 120 m (394 ft) in Montana; upper part removed by erosion.
State Montana
Name Wasatch Formation
Geologic age Tertiary
Lithologic constituents
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed, Carbonaceous)
Sedimentary > Clastic > Sandstone (Bed, Arkosic)
Sedimentary > Clastic > Conglomerate (Lens)
Sedimentary > Coal (Bed)
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)

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 Big Horn - Blaine - Chouteau - Hill - Powder River - Rosebud