Jurassic, undifferentiated (MTJu;0)

State	Montana
Name	Jurassic, undifferentiated
Geologic age	Phanerozoic \| Mesozoic \| Jurassic
Original map label	Ju
Primary rock type	fine-grained mixed clastic
Secondary rock type	limestone
Other rock types	evaporite
Lithologic constituents	Major Sedimentary > Clastic > Mixed-clastic > Sandstone-Mudstone (Bed) Minor Sedimentary > Carbonate > Limestone (Bed) Incidental Sedimentary > Chemical > Evaporite > Gypsum (Lense)
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	Tilling, R.I., Klepper, M.R., and Obradovich, J.D., 1968, K-Ar ages and time span of emplacement of the Boulder batholith, Montana: American Journal of Science, v. 266, p. 671-689. Fox, J.E., 1993, Stratigraphic cross sections showing electric logs of Upper Cretaceous and older rocks, Powder River basin, southeastern Montana and northeastern Wyoming: U.S. Geological Survey Oil and Gas Investigations Chart OC-135 to OC-138, [http://pubs.er.usgs.gov/publication/oc135] Robinson, C.S., Mapel, W.J. and Bergendahl, M.H., 1964, Stratigraphy and structure of the northern and western flanks of the Black Hills uplift, Wyoming, Montana, and South Dakota: U.S. Geological Survey Professional Paper 404, 134 p. [http://pubs.er.usgs.gov/publication/pp404] Mudge, M.R. and Rice, D.D., 1982, Lower Cretaceous Mount Pablo Formation, northwestern Montana, in Contributions to stratigraphy: U.S. Geological Survey Bulletin 1502-D, p. D1-D19. [http://pubs.er.usgs.gov/publication/b1502D] Robinson, G.D. and Barnett, H.F., 1963, Geology of the Three Forks quadrangle, Montana, with sections on petrography of igneous rocks by H.F. Barnett: U.S. Geological Survey Professional Paper 370, 143 p. [http://pubs.er.usgs.gov/publication/pp370] Cobban, W.A., 1945, Marine Jurassic formations of the Sweetgrass arch, Montana: American Association of Petroleum Geologists Bulletin, v. 29, no. 9, p. 1262-1303. Cobban, W.A., Imlay, R.W. and Reeside, J.B., Jr., 1945, Type section of Ellis formation (Jurassic) of Montana: American Association of Petroleum Geologists Bulletin, v. 29, no. 4, p. 451-453. Moberly, R., Jr., 1960, Morrison, Cloverly, and Sykes Mountain formations, northern Bighorn basin, Wyoming and Montana: Geological Society of America Bulletin, v. 71, no. 8, p. 1137-1176. Imlay, R.W., 1954, Marine Jurassic formations in the Pryor Mountains and northern Bighorn Mountains, Montana, in Richards, P.W., ed., Pryor Mountains-northern Bighorn basin, Montana, Billings Geological Society 5th Annual Field Conference Guidebook, Sept
Geographic coverage	Beaverhead - Big Horn - Blaine - Broadwater - Carbon - Cascade - Deer Lodge - Fergus - Flathead - Gallatin - Glacier - Golden Valley - Granite - Jefferson - Judith Basin - Lewis and Clark - Liberty - Madison - Meagher - Musselshell - Park - Phillips - Pondera - Powell - Silver Bow - Stillwater - Sweet Grass - Teton - Toole - Wheatland - Yellowstone