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Jurassic and Triassic rocks, undifferentiated

Jurassic and Triassic rocks, undifferentiated: in east-central Madison County where scale did not permit differentiation on map.
StateMontana
NameJurassic and Triassic rocks, undifferentiated
Geologic agePhanerozoic | Mesozoic | Triassic Jurassic
Original map labelJTR
Primary rock typefine-grained mixed clastic
Secondary rock typelimestone
Other rock typesmedium-grained mixed clastic; evaporite
Lithologic constituents
Major
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Clastic > Mixed-clastic > Sandstone-mudstone (Bed)
Minor
Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed)
Incidental
Sedimentary > Chemical > Evaporite > Gypsum (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
Kohrt, P.B., 1991, Alkalic rocks of the Judith Mountains, central Montana, in Baker, D.W., and Berg, R.B., eds., Guidebook of the Central Montana Alkalic Province--Geology, ore deposits and origin: Montana Bureau of Mines and Geology Special Publication
Wilson, A.B., and Elliott, J.E., 1997, Geologic maps of western and northern parts of Gallatin National Forest, south-central Montana: U.S. Geological Survey Geologic Investigations Series Map I-2584, 2 sheets, scale 1:126,720.
Kellogg, K.S., and Williams, V.S., 2000, Geologic map of the Ennis 30' x 60' quadrangle, Madison and Gallatin Counties, Montana, Park County, Wyoming: U.S. Geological Survey Miscellaneous Geologic Investigations Series Map I-2690, scale 1:100,000.
Geographic coverageMadison

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