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Niobrara and Frontier Formations, and Mowry and Thermopolis Shales

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Niobrara Formation (Kn) - Light-colored limestone and gray to yellow speckled limy shale. Frontier Formation (Kf) - Gray sandstone and sandy shale. Mowry Shale (Kmr) - Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. Thermopolis Shale - Black soft fissile shale; Muddy Sandstone Member at top.
State Wyoming
Name Niobrara and Frontier Formations, and Mowry and Thermopolis Shales
Geologic age Lower Cretaceous-Upper Cretaceous
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Carbonate > Limestone
Sedimentary > Clastic > Sandstone
Minor
Sedimentary > Clastic > Mudstone > Shale > Black-shale
Incidental
Sedimentary > Clastic > Mudstone > Claystone > Bentonite
References

Love, J.D. and Christiansen, A.C., 1985, Geologic Map of Wyoming: U.S. Geological Survey, scale 1:500,000.

https://pubs.er.usgs.gov/publication/70046739
NGMDB product
Counties Laramie