Triassic, undifferentiated (MTTRu;0)

State	Montana
Name	Triassic, undifferentiated
Geologic age	Phanerozoic \| Mesozoic \| Triassic
Original map label	TRu
Primary rock type	fine-grained mixed clastic
Secondary rock type	limestone
Other rock types	medium-grained mixed clastic
Lithologic constituents	Major Sedimentary > Clastic > Mixed-clastic > Sandstone-Mudstone (Bed) Minor Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed) Sedimentary > Carbonate > Limestone (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	Van Gosen, B.S., Elliott, J.E., LaRock, E.J., du Bray, E.A., Carlson, R.R., and Zientek, M.L., 2000, Generalized geologic map of the Absaroka-Beartooth study area, south-central Montana: U.S. Geological Survey Miscellaneous Field Studies Map MF-2338, sca [http://pubs.er.usgs.gov/publication/mf2338] Ruppel, E.T., O'Neill, J.M., and Lopez, D.A., 1993, Geologic map of the Dillon 1o x 2o quadrangle, Idaho and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-1803-H, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1803H] Lund, Karen, Aleinikoff, J.N., Kunk, M.J., Unruh, D.M., Zeihen, G.D., Hodges, W.C., duBray, E.A., and O'Neill, J.M., 2002, SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana: Econo 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. [http://pubs.er.usgs.gov/publication/i2584] Vuke, S.M., Wilde, E.M., Lopez, D.A., and Bergantino, R.N., 2000, Geologic map of the Lodge Grass 30' x 60' quadrangle, Montana: Montana Bureau of Mines and Geology Geologic Map 56, scale 1:100,000. Lopez, D.A., 2000, Geologic map of the Bridger 30' x 60' quadrangle, Montana: Montana Bureau of Mines and Geology Geologic Map 58, scale 1:100,000. Wulf, G.R., 1962, Lower Cretaceous Albian rocks in northern Great Plains: American Association of Petroleum Geologists Bulletin, v. 46, no. 8, p. 1371-141. Blackstone, D.L., Jr., 1975, Geology of the East Pryor Mountain quadrangle, Carbon County, Montana: Montana Bureau of Mines and Geology Special Publication 69, 13 p., 1 plate, scale 1:24,000. 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. [http://pubs.er.usgs.gov/publication/i2690] Lonn, J., 2000, Geologic map of the Lima 30' x 60' quadrangle, southwest Montana: Montana Bureau of Mines and Geology Open File Report 408, 12 p., scale 1:100,000.
Geographic coverage	Beaverhead - Big Horn - Carbon - Gallatin - Granite - Madison - Park - Silver Bow - Stillwater - Sweet Grass