Greenhorn Formation

Gray to light gray calcareous shale and shaly marl with thin beds of limestone. Shale contains white to pink calcareous specks. Marine. Thickness as much as 100 m (30–75 ft).
State Montana
Name Greenhorn Formation
Geologic age Cretaceous
Lithologic constituents
Sedimentary > Clastic > Mudstone > Shale (Bed, Calcareous)
Sedimentary > Carbonate > Limestone (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 - Carbon - Carter - Fergus - Garfield - Musselshell - Petroleum - Yellowstone