Snowcrest Range and Madison Groups; or Snowcrest Range and Tendoy Groups; or Surret Canyon through McGowan Creek Formation: Surrett Canyon, South Creek, Scott Peak, Middle Canyon, and McGowan Creek Formations

Surrett Canyon Formation: Dark gray, massive limestone with much scattered white bioclastic debris. Marine. Thickness at type section 67 m (220 ft). South Creek Formation: Dark gray, thin-bedded, chert bearing limestone that alternates with dark gray, argillaceous limestone. Marine. Thickness at type section 91 m (300 ft). Scott Peak Formation (Msp): Dark gray, chert-bearing, fine grained limestone interbedded with subordinate light brown, calcareous, quartzose siltstone to fine sandstone. Marine. Thickness at type section 685 m (2,247 ft). Middle Canyon Formation (Mmd): Dark gray, silty limestone with chert beds and nodules. Shallow marine. Thickness at type section 335 m (1,100 ft). McGowan Creek Formation: Upper part: dark gray and pale yellowish brown, thin-bedded, calcareous siltstone interbedded with dark gray, silty limestone. Lower part: dark gray, carbonaceous, thin-bedded argillite with interbeds of dark gray siltite, medium gray, fine-grained, conglomeratic sandstone and quartzite, and dark gray, silty limestone. Marine. Thickness as much as 61 m (200 ft).
State Montana
Name Snowcrest Range and Madison Groups; or Snowcrest Range and Tendoy Groups; or Surret Canyon through McGowan Creek Formation: Surrett Canyon, South Creek, Scott Peak, Middle Canyon, and McGowan Creek Formations
Geologic age Pennsylvanian and Mississippian
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Minor
Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed)
Sedimentary > Clastic > Sandstone (Bed, Calcareous)
Sedimentary > Clastic > Siltstone (Bed, Calcareous)
Metamorphic > Metasedimentary > Metaclastic > Metasiltstonesiltite
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Metamorphic > Metasedimentary > Metaclastic > Argillite
Incidental
Sedimentary > Chemical > Chert (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 Beaverhead - Madison - Silver Bow