Slim Sam Formation

Greenish gray, pyroclastic tuff and volcaniclastic-rich sandstone, siltstone, mudstone, and porcellanite. Nonmarine, locally derived from Elkhorn Mountains Volcanics. Thickness as much as 200 m (656 ft).
State Montana
Name Slim Sam Formation
Geologic age Cretaceous
Lithologic constituents
Sedimentary > Clastic > Sandstone (Tuffaceous)
Igneous > Volcanic (Pyroclastic-tuff)
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Chemical > Chert (Bed)porcellanite

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 Broadwater - Jefferson