Alaska Bench Formation: locally includes Devils Pocket Formation in central Montana

Gray and bluish gray, hard, fossiliferous limestone with subordinate interbeds of red mudstone. Marine. Thickness as much as 105 m (345 ft). In central Montana: Devils Pocket Formation: Red to gray siliceous dolomite, gray, finely crystalline, thin-bedded limestone, and red, gray, or pink, fine- to medium-grained quartz sandstone. May include massive breccia of coarse, cherty dolomite, limestone, red sandstone, shale, and chert. Intertidal to open marine. Thickness 43 m (140ft) at type section.
State Montana
Name Alaska Bench Formation: locally includes Devils Pocket Formation in central Montana
Geologic age Pennsylvanian
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Carbonate > Dolostone (Bed)
Minor
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Clastic > Sandstone (Bed)
Incidental
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Clastic > Sedimentary-breccia (Bed)May include massive breccia of coarse, cherty dolomite, limestone, red sandstone, shale, and chert
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 Fergus - Golden Valley - Musselshell