USGS Home
Contact USGS
Search USGS

Mineral Resources > Online Spatial Data > Geology > by state > Montana Geology

Geologic units in Valley county, Montana

[Additional scientific data in this geographic area]

Judith River formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 7 % of this area

Judith River formation: light-colored sandstone at top; lower third somber-gray siltstone and sandy shale; greenish-gray clay and some lignite beds; includes the Parkman sandstone member of south-central Montana.

Lithology: sandstone; mudstone; coal

Fox Hill sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 4 % of this area

Fox Hills sandstone: Typically shaly sandstone grading upward into massive brownish sandstone with white sandstone of the Colgate member locally at top.

Lithology: sandstone; mudstone

Hell Creek formation (Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary | Paleocene) at surface, covers 6 % of this area

Hell Creek formation: somber-gray sandstone and greenish shaly clay and mudstone containing dinosaur bones; a few thin lignite and subbituminous coal beds.

Lithology: sandstone; mudstone; coal

Flaxville gravel (Phanerozoic | Cenozoic | Tertiary) at surface, covers 14 % of this area

Flaxville gravel: Brown, yellow, and gray gravel, sand, and silt with marl and volcanic ash locally.

Lithology: coarse-grained mixed clastic; silt; volcanic ash

Fort Union formation (Phanerozoic | Cenozoic | Tertiary Cretaceous-Late | Paleocene) at surface, covers 3 % of this area

Fort Union formation: Clay shale, siltstone, and sandstone; local lenses of impure limestone, and numerous lignitic beds; contains Tertiary plant and animal fossils but no dinosaurs; base generally placed at the lowest of the succession of lignite beds within it; includes the Tongue River member, Lebo shale member, and Tullock member.

Lithology: shale; siltstone; sandstone; coal; limestone

Alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 6 % of this area

Alluvium: mainly valley fill consisting of silt, sand, and gravel; includes some terrace deposits and glacial drift of Pleistocene age in some areas; locally includes hot spring tufa. The older part of the alluvium, where present, is probably of Pliocene age.

Lithology: alluvium; glacial drift; carbonate

playa (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

playa

Lithology: playa

Claggett formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 3 % of this area

Claggett formation: chiefly dark-gray shale with iron-stained concretions; locally sandstone present; numerous bentonite beds near base.

Lithology: shale; sandstone; bentonite

Bearpaw shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 54 % of this area

Bearpaw shale: Dark-gray and brownish clay shale; thick units of nonfissile bentonitic shale; calcareous and ferruginous concretions throughout; contains some thick bentonite beds.

Lithology: shale; sandstone; bentonite