Oligocene nonmarine rocks (WAOGc;0)

State	Washington
Name	Oligocene nonmarine rocks
Geologic age	Oligocene
Original map label	OLc
Comments	Includes very small outcrop in southern Stevens County which has been mapped as Gerome Andesite (note, however, that Stoffel and others, 1991, report that while the term "Gerome Andesite" was once widely used, it has since been abandoned). Some discrepancy over the lithology near Republic: Muessig, 1967, identifies the Tom Thumb Tuff Member as thin-bedded fine tuff while Stoffel, 1990, identifies it as primarily fossiliferous shale beds. The Eagle Creek Formation is almost entirely volcanic material: mostly andesite flows, tuff, and breccia, with some trachyte, trachyandesite, and basalt; lithology and stratigraphy suggests contemporaneity with Fifes Peak andestite (see WAOLMv) (Warren, 1941).
Primary rock type	conglomerate
Secondary rock type	tuff
Other rock types	breccia; sandstone; siltstone; coal; clay or mud; basalt; andesite
Lithologic constituents	Major Sedimentary > Clastic > Conglomerate (Tuffaceous) Minor Sedimentary > Clastic > Sandstone (Tuffaceous) Igneous > Volcanic > Mafic-volcanic (Pyroclastic, tuff)Includes "lake beds" of Ferry County (Muessig, 1967). Referred to as "volcanic tuff" in literature; assumed to be mafic because of local andesite and basalt flows in both this unit and adjacent units. Incidental Igneous > Volcanic > Mafic-volcanic (Volcaniclastic, volcanic breccia)Referred to as "volcanic breccia" in literature; assumed to be mafic because of local andesite and basalt flows in both this unit and adjacent units. Igneous > Volcanic > Mafic-volcanic > Basalt Unconsolidated > Fine-detrital > Clay Sedimentary > Coal > Lignite Sedimentary > Clastic > Siltstone (Tuffaceous)Possibly of minor rank, but in less abundance than sandstone. Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)
Map references	Huntting, M. T., Bennett, W. A. G., Livingston, V. E. Jr., Moen, W. S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.
Unit references	Huntting, M. T., Bennett, W. A. G., Livingston, V. E. Jr., 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. Warren, W. C., 1941, Relation of the Yakima Basalt to the Keechelus Andesite Series: The Journal of Geology, v. 49, p. 795-814. Muessig, S., 1967, Geology of the Republic Quadrangle and a Part of the Aeneas Quadrangle, Ferry County, Washington: U. S. Geological Survey Bulletin 1216, 135 p. [http://pubs.er.usgs.gov/publication/b1216] 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. Roberts, A. E., 1958, Geology and Coal Resources of the Toledo-Castle Rock District, Cowlitz and Lewis Counties, Washington: U. S. Geological Survey Bulletin 1062, 71 p, 6 pls. [http://pubs.er.usgs.gov/publication/b1062] Phillips, W. M., 1987, Geologic Map of the Vancouver Quadrangle, Washington and Oregon: Washington Division of Geology and Earth Resources Open File Report 87-10, scale 1:100,000. Korosec, M. A., 1987, Geologic Map of the Hood River Quadrangle, Washington and Oregon: Washington Division of Geology and Earth Resources Open File Report 87-6, scale 1:100,000. Becraft, G. E. and Weis, P. L., 1963, Geology and Mineral Deposits of the Turtle Lake Quadrangle, Washington: U. S. Geological Survey Bulletin 1131, 73 p., 2 pls. [http://pubs.er.usgs.gov/publication/b1131] Stoffel, K. L., 1990, Geologic Map of the Republic 1:100,000 Quadrangle, Washington: Washington Division of Geology and Earth Resources Open File Report 90-10, 62 p, 1 pl.
Geographic coverage	Cowlitz - Ferry - Klickitat - Skagit - Skamania - Snohomish - Stevens