Mission Canyon Formation: locally includes Big Snowy Formation in south-central Montana

Gray, massive limestone with chert beds and nodules, and solution breccia zones. Shallow marine. Thickness as much as 520 m (1,706 ft). In south-central Montana - Big Snowy Formation: Olive gray, thick-bedded limestone, yellowish gray siltstone, dark gray shale, and yellowish brown, thin bedded siltstone and mudstone. Nearshore marine. Thickness 120 m (394 ft).
State Montana
Name Mission Canyon Formation: locally includes Big Snowy Formation in south-central Montana
Geologic age Mississippian
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Minor
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone (Bed)
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 - Blaine - Broadwater - Cascade - Fergus - Gallatin - Golden Valley - Jefferson - Judith Basin - Lewis and Clark - Madison - Meagher - Phillips - Wheatland