Fort Union Formation

No unique unit description on map. Assumed to include undivided Tertiary age members of the Fort Union Formation: Sentinel Butte (Tfsb), Tongue River (Tftr), Linley (Tflc), Ludlow (Tfld), Lebo (Tfle), Ekalaka (Tfe), and Tullock (Tft) members.
State Montana
Name Fort Union Formation
Geologic age Tertiary
Lithologic constituents
Major
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed, Carbonaceous)
Sedimentary > Clastic > Sandstone (Bed)
Minor
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)
Incidental
Sedimentary > Coal (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 Blaine - Chouteau - Hill