Devonian, undifferentiated (MTDu;0)

State	Montana
Name	Devonian, undifferentiated
Geologic age	Phanerozoic \| Paleozoic \| Devonian
Original map label	Du
Primary rock type	carbonate
Secondary rock type	fine-grained mixed clastic
Other rock types	conglomerate; sedimentary breccia; evaporite
Lithologic constituents	Major Sedimentary > Clastic > Mixed-clastic > Siltstone-Mudstone (Bed) Sedimentary > Carbonate (Bed) Minor Sedimentary > Clastic > Sedimentary-breccia (Bed) Sedimentary > Clastic > Conglomerate (Bed) Incidental Sedimentary > Chemical > Evaporite > Anhydrite (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	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] O'Neill, J.M., Christiansen, R.L., 2002, Geologic map of the Hebgen Lake quadrangle: Montana Bureau of Mines and Geology Open File Report 464, 21 p, scale 1:100,000. Lopez, D.A., 2001, Geologic map of the Sweet Grass Hills 30' x 60' quadrangle, north-central Montana: Montana Bureau of Mines and Geology Open File Report 443, 4 p., scale 1:100,000. 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] Mudge, M.R., Earhart, R.L., 1983, Geologic and structure maps of the Choteau 1° x 2° quadrangle, western Montana: United States Geological Survey Miscellaneous Geologic Investigations Series Map I-1300, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1300] Harrison, J.E., Whipple, J.W., and Lidke, D.J., 1998, Geologic map of the western part of the Cut Bank 1° x 2° quadrangle, northwestern Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Series Map I-2593, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i2593] Richards, P.W., 1955, Geology of the Bighorn Canyon-Hardin area, Montana and Wyoming: U.S. Geological Survey Bulletin 1026, 96 p., (incl. geologic map, scale 1:62,500). [http://pubs.er.usgs.gov/publication/b1026] Klepper, M.R., Weeks, R.A. and Ruppel, E.T., 1957, Geology of the southern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana: U.S. Geological Survey Professional Paper 292, 82 p. [http://pubs.er.usgs.gov/publication/pp292] 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. 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. Richards, R.W., 1955, Geology of the Bighorn Canyon-Hardin area, Montana and Wyoming: U.S. Geological Survey Bulletin 1026, 93 p., 7 plates. [http://pubs.er.usgs.gov/publication/b1026] Sandberg, C.A. and Hammond, C.R., 1958, Devonian system in Williston basin and central Montana: American Association of Petroleum Geologists Bulletin, v. 42, no. 10, p. 2293-2334. Hayes, M.D., 1985, Conodonts of the Bakken Formation, Williston basin, North Dakota: The Mountain Geologist, v. 22, no. 2, p. 64-77. Sandberg, C.A. and Klapper, Gilbert, 1967, Stratigraphy, age, and paleotectonic significance of the Cottonwood Canyon Member of the Madison Limestone in Wyoming and Montana, in Contributions to general geology, 1967: U.S. Geological Survey Bulle [http://pubs.er.usgs.gov/publication/b1251B] Sandberg, C.A., 1967, Exshaw Formation of Devonian and Mississippian age in northwestern Montana, in Hayes, P.T., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1966: U.S. Geological Survey Bulletin 1254-A, p. A39-A41. [http://pubs.er.usgs.gov/publication/b1254A] Sando, W.J., 1982, New members of the Madison Limestone (Devonian and Mississippian), north-central Wyoming and southern Montana, in Stratigraphic notes, 1980-1982: U.S. Geological Survey Bulletin 1529-H, p. H125-H130. [http://pubs.er.usgs.gov/publication/b1529H] Macke, D.L., 1993, Cambrian through Mississippian rocks of the Powder River basin, Wyoming, Montana, and adjacent areas, in Evolution of sedimentary basins--Powder River basin: U.S. Geological Survey Bulletin 1917-M, p. M1-M174 [http://pubs.er.usgs.gov/publication/b1917M] Sandberg, C.A., 1961, Widespread Beartooth Butte Formation of Early Devonian age in Montana and Wyoming and its paleogeographic significance: American Association of Petroleum Geologists Bulletin, v. 45, no. 8, p. 1301-1309. McMannis, W.J., 1962, Devonian stratigraphy between Three Forks, Montana and Yellowstone Park, in The Devonian System of Montana and adjacent areas--Three Forks-Belt Mountains area and symposium: Billings Geological Society Guidebook, no. 13, Sandberg, C.A., 1965, Nomenclature and correlation of lithologic subdivisions of the Jefferson and Three Forks Formations of southern Montana and northern Wyoming, in Contributions to stratigraphy: U.S. Geological Survey Bulletin 1194-N, p. N [http://pubs.er.usgs.gov/publication/b1194N] Sloss, L.L., and Moritz, C.A., 1951, Paleozoic stratigraphy of southwestern Montana: American Association of Petroleum Geologists Bulletin, v. 35, no. 10, p. 2135-2169 McMannis, W.J., 1955, Geology of the Bridger Range, Montana: Geological Society of America Bulletin, v. 66, no. 11, p. 1385-1430. Sandberg, C.A., and McMannis, W.J., 1964, Occurrence and paleogeographic significance of the Maywood Formation of Late Devonian age in the Gallatin Range, southwestern Montana, in Geological Survey research 1964: U.S. Geological Survey Profes [http://pubs.er.usgs.gov/publication/pp501C] Sloss, L.L., and Laird, W.M., 1947, Devonian System in central and northwestern Montana: American Association of Petroleum Geologists Bulletin, v. 31, no. 8, p. 1404-1430. Shank, S.G., and Eggler, D.H., 1991, Petrology and geochemistry of the Rocky Boy stock, Bearpaw Mountains, Montana--Evolution of shonkinite and monozite magmas, in Baker, D.W., and Berg, R.B., eds., Guidebook of the Central Montana Alkalic Province--Geol
Geographic coverage	Beaverhead - Big Horn - Blaine - Broadwater - Carbon - Cascade - Deer Lodge - Flathead - Gallatin - Granite - Jefferson - Judith Basin - Lewis and Clark - Madison - Meagher - Park - Phillips - Pondera - Powell - Silver Bow - Stillwater - Sweet Grass - Teton - Wheatland