Sphinx Formation

Reddish gray sandstone and conglomerate. Clasts dominantly carbonate and quartzite. Syntectonic alluvial fan. Thickness over1,000 m (3,281 ft).
State Montana
Name Sphinx Formation
Geologic age Cretaceous
Lithologic constituents
Major
Sedimentary > Clastic > Conglomerate
Sedimentary > Clastic > Sandstone
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 Madison