Yellowish gray to very pale orange, angular silt and clay-size sediment with lenses of angular and subangular locally derived rock ranging to very large boulder size but generally cobble size and smaller. In some areas granules and pebbles float in the silty matrix. Locally cemented; clasts may be coated with calcium carbonate, especially near the base. Thickness as much as 200 ft.
State Montana
Name Sediment
Geologic age Quaternary and Tertiary
Lithologic constituents
Unconsolidated > Fine-detrital > Silt
Unconsolidated > Fine-detrital > Clay
Unconsolidated > Coarse-detrital > Gravel

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 Jefferson - Madison