Chugwater and Goose Egg Formations

Chugwater Formation (TRc): Red siltstone, sandstone, and shale with subordinate gypsum and local limestone bed at top. Shallow restricted marine and nonmarine. Thickness as much as 180 m (590 ft). Goose Egg Formation: Red shale and sandstone with some interbeds of anhydrite, gypsum, and limestone. Nearshore marine, marine, and restricted marine. Thickness 30 m (98 ft).
State Montana
Name Chugwater and Goose Egg Formations
Geologic age Triassic and Permian
Lithologic constituents
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Chemical > Evaporite > Gypsum (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Chemical > Evaporite > Anhydrite (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