Hell Creek and Fox Hills Formations

Hell Creek Formation (Khc): Light gray, bentonitic claystone that alternates with gray to brown sandstone interbedded with carbonaceous shale. Laterally equivalent to Lance Formation. Fluvial and flood plain. Thickness as much as 335 m (1,100 ft). Fox Hills Formation (Kfh): Yellowish orange to gray, fine- to medium-grained, non-calcareous sandstone in upper part, and interbedded sandstone, siltstone, and black shale with calcareous concretion zone in lower part. Marginal marine. Thickness 30–45 m (98–148 ft).
State Montana
Name Hell Creek and Fox Hills Formations
Geologic age Cretaceous
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed, Carbonaceous)
Minor
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed, Calcareous)
Sedimentary > Clastic > Siltstone (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 - Phillips - Valley