St. Mary River Formation

Gray calcareous shale and siltstone with lenticular argillaceous sandstone and thin interbeds of black, nodular limestone. Lagoonal and fluvial. Thickness as much as 300 m (948 ft).
State Montana
Name St. Mary River Formation
Geologic age Cretaceous
Lithologic constituents
Major
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed, Calcareous)
Sedimentary > Clastic > Sandstone (Lens)
Minor
Sedimentary > Carbonate > Limestone (Bed)
References

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 Glacier - Lewis and Clark - Pondera - Teton