Oligocene-Miocene volcanic rocks

Andesite flow breccia, andesite flows, and minor tuff beds; includes some basalt flows and flow breccia. Commonly more massive and less altered than similar-appearing Eocene-Oligocene volcanic rocks. Clastic flows and flows of black glass, and course to fine-grained clastic and pyroclastic rocks in the Republic and Curlew areas of Ferry County.
State Washington
Name Oligocene-Miocene volcanic rocks
Geologic age Miocene
Lithologic constituents
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia)
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia)
Igneous > Volcanic > Felsic-volcanic > Dacite (Pyroclastic-tuff)
Sedimentary > Clastic > Conglomerate (Bed, Tuffaceous)Volcaniclastic.
Sedimentary > Clastic > Sandstone (Bed)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic-tuff)
Comments Some recent maps show that some of this unit is mostly dacite (Luedke, 1998, Stoffel and others, 1991). Others maintain that it is mostly andesite (Walsh and others, 1987). Fifes Peak andesite and upper part of Keechelus andesite in the Mt. Aix Quadrangle are the same unit (Warren, 1941).
Stratigraphic units Fifes Peak andesite (upper part of Keechelus andesite, some of lower part); Taneum andesite; Klondike Mtn Formation

Huntting, M.T., Bennett, W.A.G., Livingston, V.E.Jr., and Moen, W.S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.

Walsh, T.J., Korosec, M.A., Phillips, W.M., Logan, R.T., Schasse, H.W., 1987, Geologic Map of Washington-Southwest Quadrant: Washington Division of Geology and Earth Resources, Geologic Map GM-34, scale 1:250,000.

Luedke, Robert G., 1998, Maps showing distribution, composition, and age of Early and Middle Cenozoic volcanic centers in Oregon and Washington: U.S. Geological Survey Miscellaneous Investigations Series Map I-2291-D, scale 1:1,000,000.


Warren, W.C., 1941, Relation of the Yakima Basalt to the Keechelus Andesite Series: The Journal of Geology, v. 49, p. 795-814.

Parker, R.L. and Calkins, J.A., 1964, Geology of the Curlew Quadrangle Ferry County Washington, U.S. Geological Survey Bulletin 1169, 95 p.


Stoffel, K.L., Joseph, N.L., Waggoner, S.Z., Gulick, C.W., Korosec, M.A., Bunning, B.B., 1991, Geologic Map of Washington--Northeast Quadrant: Washington Division of Geology and Earth Resources Geologic Map, GM-39, scale 1:250,000.

Tabor, R.W., Waitt, R.B.,Jr., Frizzell, V.A.,Jr., Swanson, D.A., Byerly, G.R., Bentley, R.D., 1982, Geologic Map of the Wanatchee 1:100,000 Quadrangle, Central Washington: U. S. Geological Survey Miscellaneous Investigations Series Map I-1311, scale 1:100,000.

Dragovich, J.D., Logan, R.L., Schasse, H.W., Walsh, T.J., Lingley, W.S., Jr., Norman, D.K., Gerstel, W.J., Lapen, T.J., Schuster, J.E., Meyers, K.D., 2002, Geologic Map of Washington-Northwest Quadrant: Washington Division of Geology and Earth Resources Geologic Map GM-50, scale 1:250,000.

NGMDB product
Counties Clark - Ferry - King - Kittitas - Lewis - Pierce - Skamania - Yakima