Cretaceous volcanic rocks (MTKv;0)

State	Montana
Name	Cretaceous volcanic rocks
Geologic age	Phanerozoic \| Mesozoic Cenozoic \| Cretaceous-Late Tertiary
Original map label	Kv
Primary rock type	volcanic rock (aphanitic)
Secondary rock type	fine-grained mixed clastic
Other rock types
Lithologic constituents	Major Igneous > VolcanicMany types of volcanic and hypabyssal forms are represented by this map unit, such as lava flows, tuffs, lahars, stocks, dikes, and sills. Likewise, a wide variety of igneous lithologies are included; most are intermediate in composition, but mafic to felsic compositions are included. Also, volcaniclastic and clastic sedimentary rocks are interlayered with the volcanics. Minor Sedimentary > Clastic > Mixed-clastic > Sandstone-Mudstone (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	Roberts, A.E., 1972, Cretaceous and early Tertiary depositional and tectonic history of the Livingston area, southwestern Montana, in Geology of the Livingston area, southwestern Montana: U.S. Geological Survey Professional Paper 526-C, p. C1 [http://pubs.er.usgs.gov/publication/pp526C] 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] Lewis, R.S., 1998, Preliminary geologic map of the Butte 1° x 2° quadrangle: Montana Bureau of Mines and Geology Open File Report 363, 16 p, scale 1:250,000. du Bray, E.A., Elliott, J.E., Van Gosen, B.S., LaRock, E.J., and West, A.W., 1994, Reconnaissance geologic map of the Sliderock Mountain area, Sweet Grass and Stillwater Counties, Montana: U.S. Geological Survey Miscellaneous Field Studies Map MF-2259, 1 [http://pubs.er.usgs.gov/publication/mf2259] Vuke, S.M., 2000, Geologic map of the Great Falls South 30' x 60' quadrangle, central Montana: Montana Bureau of Mines and Geology Open File Report 407, scale 1:100,000. Porter, K.W., Wilde, E.M., 1993, Preliminary geologic map of the Lewistown 30' x 60' quadrangle, revised 1999: Montana Bureau of Mines and Geology Open File Report 308, 22 p, scale 1:100,000. Tysdal, R.G., Ludington, Steve, and McCafferty, A.E., 1996, Mineral and energy resource assessment of the Helena National Forest, west-central Montana: U.S. Geological Survey Open-File Report 96-683-A, 322 p., 6 plates. [http://pubs.er.usgs.gov/publication/ofr96683A] Richards, P.W., 1957, Geology of the area east and southeast of Livingston, Park County, Montana: U.S. Geological Survey Bulletin 1021-L, p. 385-438. [http://pubs.er.usgs.gov/publication/b1021L] 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] Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana: U.S. Geological Survey Professional Paper 428, 101 p., 18 plates. [http://pubs.er.usgs.gov/publication/pp428] Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: U.S. Geological Survey Bulletin 1151, 121 p., 7 plates. [http://pubs.er.usgs.gov/publication/b1151] Smedes, H.W., 1966, Geology and igneous petrology of the northern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana: U.S. Geological Survey Professional Paper 510, 116 p. [http://pubs.er.usgs.gov/publication/pp510] Pearson, R.C., and Childs, J.F., 1989, Field trip guide, road log, and summary of Cretaceous volcanic geology, Dillon to Bannack, Beaverhead County, Montana: Northwest Geology, v. 18, p. 36-59.
Geographic coverage	Broadwater - Cascade - Deer Lodge - Jefferson - Lewis and Clark - Madison - Meagher - Park - Powell - Stillwater - Sweet Grass