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Arikaree formation

Arikaree formation: gray sandstone with layers of concretions; contains volcanic ash and, locally, channels filled with conglomerate; known only in southeastern Montana.
State Montana
Name Arikaree formation
Geologic age Phanerozoic | Cenozoic | Tertiary
Primary rock type sandstone
Secondary rock type tuff
Other rock types conglomerate
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed)
Minor
Igneous > Volcanic (Pyroclastic, air fall)
Sedimentary > Clastic > Conglomerate (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
Denson, N.M., Gibson, M.L. and Sims, G.L., 1992, Geologic and structure map of the north half of the Powder River basin, southeastern Montana and northeastern Wyoming: U.S. Geological Survey Miscellaneous Investigations Series Map I-2281-A, 1
Denson, N.M., and Gill, J.R., 1965, Uranium-bearing lignite and carbonaceous shale in the southwestern part of the Williston Basin--A regional study: U.S. Geological Survey Professional Paper 463, 75 p., 19 plates.
Denson, N.M., Macke, D.L. and Schumann, R.R., 1990, Geologic map and distribution of heavy minerals in Tertiary rocks of the Sheridan 30' x 60' quadrangle, Wyoming and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-
Counties Carter