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Rhyolite, andesite, dacite, quartz latite; Oligocene to Eocene volcanics; northern Idaho;

Lower Tertiary, possibly Oligocene, flows and tuffs of northern Idaho.
StateIdaho
NameRhyolite, andesite, dacite, quartz latite; Oligocene to Eocene volcanics; northern Idaho;
Geologic agePaleogene, possibly Oligocene
Original map labelTov
CommentsKamiah Volcanics form Kamiah Buttes, a group of buttes that rise 1000 ft above surrounding flows of Columbia River basalt on the Clearwater Plateau (ID130, ID131). A lower quartz latite unit (chemically rhyolite flows and air-fall tuff) is overlain by an andesitic unit (andesite, basaltic andesite and basalt, flows and pyroclastic rocks). Potato Hill volcanics are rhyolitic and dacitic welded ash-flow tuff, subvolcanic intrusives, and volcanic breccia (ID132). Minimum age is Oligocene (older than overlying Miocene basalt of Columbia River Group. Maximum age is Eocene. Jones (1982) suggested Kamiah Volcanics correlate with Eocene Challis volcanics (ID130). Isotopically dated Eocene dikes are present 12 km southwest of Potato Hill (ID132). Steep flow foliation and volcanic breccia at Potato Hill may indicate an eruptive center, perhaps a small caldera. Flat flow layering in Kamiah volcanics may indicate undeformed outflow.
Primary rock typerhyolite
Secondary rock typeandesite
Other rock typesignimbrite; lava flow; volcanic breccia (agglomerate)
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)andesite, basaltic andesite, and basalt flows of Kamiah Volcanics
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic, ash-flow)rhyolitic welded ash-flow tuff of Potato Hill volcanics
Minor
Igneous > Volcanic > Felsic-volcanic > Quartz-latite (Flow)quartz latite (chemically rhyolite) flows of Kamiah Volcanics
Igneous > Volcanic > Felsic-volcanic > Dacite (Pyroclastic, ash-flow)dacitic welded ash-flow tuff of Potato Hill volcanics
Incidental
Igneous > Volcanic > Felsic-volcanic (Volcaniclastic, volcanic breccia)clast-rich volcanic rocks with volcanic and granitoid clasts
Igneous > Volcanic > Mafic-volcanic > Andesite (Pyroclastic)lapillistone, tuff breccia, top and bottom flow breccias
Igneous > Volcanic > Felsic-volcanic (Pyroclastic, air fall)air-fall tuffs of Kamiah Volcanics
Map references
Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000.
Unit references
Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000.
Rember, W.C. and Bennett, E.H., 1979, Geologic map of the Pullman quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Pullman 2o Quadrangle, scale 1:250,000.
Jones, R.W., 1982, Early Tertiary-age Kamiah volcanics, north-central Idaho: in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic Geology of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology Bulletin 26, p. 43-52.
Kauffmann, J.D., Lewis, R.S., and Myers, P.E., in prep., Geologic map of the Kamiah quadrangle, Lewis and Idaho Counties, Idaho: Moscow, Idaho, Idaho Geological Survey, 1:24,000 scale.
Lewis, R.S., and others, in prep., Geologic map of the Potlatch 30' x 60' quadrangle, Idaho: Moscow, Idaho, Idaho Geological Survey, 1:100,000 scale.
Geographic coverageIdaho - Latah

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