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Tertiary volcanic rocks

Tertiary volcanic rocks: Flows and associated pyroclastic deposits, with subordinate amounts of intercalated sedimentary beds and lignite. The volcanic material is mostly latite, quartz latite, and andesite but includes some rhyolite and basalt. The distinction between Tertiary and pre-Tertiary volcanic rocks was not made in some of the reports used in the complilation. Hence in the less well-known areas some pre-Tertiary volcanic rocks may be included.
StateMontana
NameTertiary volcanic rocks
Geologic agePhanerozoic | Cenozoic | Tertiary
Original map labelTv
CommentsThis unit is highly lumped and generalized, and includes a wide variety of volcanic rock lithologies and forms, representing a number of geographically and geologically distinct intrusive centers and provinces.
Primary rock typevolcanic rock (aphanitic)
Secondary rock typemixed clastic/volcanic
Other rock typescoal
Lithologic constituents
Major
Igneous > Volcanic (Volcaniclastic)
Igneous > Volcanic
Incidental
Sedimentary > Coal (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
Smedes, H.W., and Prostka, H.J., 1972, Stratigraphic framework of the Absaroka Volcanic Supergroup in the Yellowstone National Park region: U.S. Geological Survey Professional Paper 729-C, 33 p.
Chadwick, R.A., 1970, Belts of eruptive centers in the Absaroka-Gallatin volcanic province, Wyoming-Montana: Geological Society of America Bulletin, v. 81, no. 1, p. 267-273.
Chadwick, R.A., 1982, Geologic map of the Fridley Peak quadrangle, Montana: Montana Bureau of Mines and Geology Geologic Map Series No. 31, scale 1:62,500.
Witkind, I.J., 1969, Geology of the Teepee Creek quadrangle, Montana-Wyoming: U.S. Geological Survey Professional Paper 609, 101 p., scale 1:62,500.
Witkind, I.J., 1972, Geologic map of the Henrys Lake quadrangle, Idaho and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-781-A, scale 1:62,500.
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.
M'Gonigle, J.W., and Dalrymple, G.B., 1996, 40Ar/39Ar ages of some Challis Volcanic Group rocks and the initiation of Tertiary sedimentary basins in southwestern Montana: U.S. Geological Survey Bulletin 2132, 17 p., 1 plate.
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.
Bergantino, R., Porter, K.W., 2002, Geologic map of the Rocky Boy 30'x 60' map: Montana Bureau of Mines and Geology Open File Report 451, 16 p, scale 1:100,000.
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.
Trombetta, J.T., 1987, Evolution of the Eocene Avon volcanic complex, Powell County, Montana: Bozeman, Montana State University, M.S. thesis, 97 p.
Berg, R.B., Vuke, S.M., 2002, Geologic map of the Fort Benton 30' x 50' quadrangle: Montana Bureau of Mines and Geology Open File Report 460, 7 p., scale 1:100,000.
Chadwick, R.A., 1972, Volcanism in Montana: Northwest Geology, v. 1, p. 1-20.
Tureck-Schwartz, Kathy, and Hyndman, D.W., 1991, High-potassium igneous rocks of the Bearpaw Mountains, north-central Montana, in Baker, D.W., and Berg, R.B., eds., Guidebook of the Central Montana Alkalic Province--Geology, ore deposits and origin: Mont
Harlan, S.S., Mehnert, H.H., Snee, L.W., and Meen, J.K., 1991, Preliminary isotopic (K-Ar and 40Ar/39Ar age determinations from selected Late Cretaceous and Tertiary igneous rocks in Montana, in Baker, D.W., and Berg, R.B., eds., Guidebook of the Central
Dahl, G.G., Jr., 1971, General geology of the area drained by the North Fork of the Smith River, Meagher County, Montana: Butte, Montana College of Mineral Science and Technology, M.S. thesis.
Sears, J.W., 1985, Middle Eocene tuff from the Missoula basin, west-central Montana: Northwest Geology, v. 14, p. 33-36.
Kirchner, Gail, 1983, Calc-alkaline and alkaline magmatism in Linster Peak dome, Judith Mountains, Montana: Northwest Geology, v. 12, p. 63-73.
Chadwick, R.A., 1978, Geochronology of post-Eocene rhyolitic and basaltic volcanism in south-western Montana: Isochron/West, no. 22, p. 25-28.
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 coverageBeaverhead - Blaine - Broadwater - Cascade - Chouteau - Deer Lodge - Flathead - Gallatin - Granite - Hill - Jefferson - Judith Basin - Lewis and Clark - Madison - Meagher - Mineral - Missoula - Park - Powell - Ravalli - Sanders - Silver Bow - Sweet Grass

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