Thermopolis shale (MTKt;0)

State	Montana
Name	Thermopolis shale
Geologic age	Phanerozoic \| Mesozoic \| Cretaceous-Early
Original map label	Kt
Comments	Many areas on the map shown as Kc include rocks that are mapped separately on more modern maps as Thermopolis Shale.
Primary rock type	mudstone
Secondary rock type	sandstone
Other rock types	bentonite
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Bed) Sedimentary > Clastic > Mudstone (Bed) Incidental Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)
Map references	Ross, P.R., Andrews, D.A., and Witkind, I.J., 1955, Geologic map of Montana: U.S. Geological Survey, 2 sheets, scale 1:500,000.
Unit references	Roberts, A.E., 1972, Cretaceous and early Tertiary depositional and tectonic history of the Livingston area, southwestern Montana, in Geology of the Livingston area, southwestern Montana: U.S. Geological Survey Professional Paper 526-C, p. C1 [http://pubs.er.usgs.gov/publication/pp526C] O'Neill, J.M., Christiansen, R.L., 2002, Geologic map of the Hebgen Lake quadrangle: Montana Bureau of Mines and Geology Open File Report 464, 21 p, scale 1:100,000. Tysdal, R.G., Ludington, Steve, and McCafferty, A.E., 1996, Mineral and energy resource assessment of the Helena National Forest, west-central Montana: U.S. Geological Survey Open-File Report 96-683-A, 322 p., 6 plates. [http://pubs.er.usgs.gov/publication/ofr96683A] Lopez, D.A., 2000, Geologic map of the Billings 30' x 60' quadrangle, Montana: Montana Bureau of Mines and Geology Geologic Map 59, scale 1:100,000. Fraser, G.D., Waldrop, H.A. and Hyden, H.J., 1969, Geology of the Gardiner area, Park County, Montana: U.S. Geological Survey Bulletin 1277, 118 p. [http://pubs.er.usgs.gov/publication/b1277] Tysdal, R.G., Dyman, T.S. and Nichols, D.J., 1989, Correlation chart of Lower Cretaceous rocks, Madison Range to Lima Peaks area, southwestern Montana: U.S. Geological Survey Miscellaneous Field Studies Map MF-2067, 15 p., 1 sheet. [http://pubs.er.usgs.gov/publication/mf2067] Lopez, D.A., 2000, Geologic map of the Bridger 30' x 60' quadrangle, Montana: Montana Bureau of Mines and Geology Geologic Map 58, scale 1:100,000. Tysdal, R.G., Dyman, T.S. and Nichols, D.J., 1989, Lower Cretaceous bentonitic strata in southwestern Montana assigned to Vaughn Member of Mowry Shale (east) and of Blackleaf Formation (west): The Mountain Geologist, v. 26, no. 2, p. 53-61. Knechtel, M.M., 1959, Stratigraphy of the Little Rocky Mountains and encircling foothills, Montana, in Contributions to economic geology: U.S. Geological Survey Bulletin 1072-N, p. N723-N752. [http://pubs.er.usgs.gov/publication/b1072N]
Geographic coverage	Big Horn - Carbon - Yellowstone