Judith River and Claggett Formations

Judith River Formation (Kjr): Light brown to light gray, fine- to coarse-grained sandstone with interbeds of gray to black carbonaceous shale, silty shale, and thin coal. Local Parkman Sandstone Member (lower part of formation):yellowish gray to brownish gray and olive green, fine- to medium-grained, cross-bedded sandstone interbedded with yellowish gray, silty shale. Estuarine, brackish, and nearshore marine. Thickness as much as 305 m (1000 ft). Claggett Formation (Kcl): Dark gray to gray shale that weathers brown, with thin, gray sandstone laminae and beds in upper or middle part and calcareous concretions in lower part. Marine. Thickness as much as 170 m (558 ft).
State Montana
Name Judith River and Claggett Formations
Geologic age Cretaceous
Lithologic constituents
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed, Carbonaceous)
Sedimentary > Clastic > Mixed-clastic > Siltstone-mudstone (Bed)silty shale
Sedimentary > Coal (Bed)

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 Chouteau - Fergus - Garfield - Judith Basin - Musselshell - Petroleum