Jeffferson through Snowy Range Formation: Jefferson, Maywood(?), Beartooth Butte(?), and Snowy Range Formations in Big Snowy Mountains

Jefferson Formation (Dj): Birdbear Member (upper part of formation): light to medium gray, sucrosic dolomite. Lower part of formation: grayish black, commonly petroliferous dolomite or limestone that may be interbedded with light gray quartzite. Marine. Thickness as much as 520 m (1,706 ft). Maywood Formation: Thin-bedded dolomitic limestone and dolomite interbedded with calcareous shale. Shallow marine. Thickness as much as 120 m (394 ft). Beartooth Butte Formation: Light gray and grayish red dolomite and limestone breccia and conglomerate, sandy and silty dolomite, and dolomitic siltstone, sandstone, and shale. Isolated outcrops throughout central Montana. Estuarine. Thickness as much as 50 m (164 ft). Snowy Range Formation (CAsr): Sage Member (upper part of formation): gray limestone and grayish green shale interbedded with grayish green flat-pebble conglomerate. Dry Creek Member (lower part of formation): greenish gray shale and grayish orange calcareous sandstone. Shallow marine. Thickness as much as 85 m (280 ft).
State Montana
Name Jeffferson through Snowy Range Formation: Jefferson, Maywood(?), Beartooth Butte(?), and Snowy Range Formations in Big Snowy Mountains
Geologic age Devonian through Cambrian
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed, Calcareous)
Sedimentary > Carbonate > Dolostone (Bed)
Minor
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Sandstone (Bed, Calcareous)
Sedimentary > Clastic > Conglomerate (Bed)
Incidental
Metamorphic > Metasedimentary > Metaclastic > Quartzite
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