Upper Eocene volcanic rocks

Predominantly basalt flows and flow breccia; includes some pyroclastic and andesite rocks. Chiefly in western Washington.
State Washington
Name Upper Eocene volcanic rocks
Geologic age Late Eocene to Oligocene
Lithologic constituents
Igneous > Volcanic > Mafic-volcanic > Basaltic-andesite (Flow)
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow, Pyroclastic-tuff, Volcaniclastic-volcanic breccia)
Igneous > Volcanic > Felsic-volcanic > Dacite (Flow)
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)
Sedimentary > Clastic (Tuffaceous)Water-laid tuff"" of Robert 1958.
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Clastic > Conglomerate (Bed)
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow)
Sedimentary > Clastic > Siltstone (Bed)
Comments Luedke, 1998, indicates that this unit has a large volume of andesite as compared to basalt. Walsh and others, 1987, indicate that this unit is almost entirely basaltic andesite flows of Oligocene to Eocene age with minor andesite, dacite, and basalt flows, and thin interbeds of shale, tuff, and volcanic sandstone. Hatchet Mountain formation consists of a base of basaltic conglomerate, sandstone, and water-laid tuff, underlying 2750 feet of basaltic and andesitic lava flows, flow breccia, pyroclastic,and tuffaceous sedimentary rocks. Increase in thickness to south and east as Cowlitz changes from marine to nonmarine (Roberts, 1958). Roberts, 1958, also suggests that Goble volcanic series includes Hatchet Mountain and parts of the Cowlitz and Toutle Formations (see WAOlv) as opposed to being contained within the Cowlitz formation. Phillips, 1987, maps the portion of the unit south of the Lewis River as basaltic-andesite and basalt flows with interbedded tuff and basaltic sandstone and conglomerate. North of the Lewis River are basaltic-andesite lava flows and flow breccia of the Goble Volcanics with interbedded sedimentary rocks. Small polygon in northern Ferry County tagged as WAEv1b in digital coverage is really WATas in original map.
Stratigraphic units Cowlitz formation (in part: Goble volcanic member, Pe Ell volcanic member); Hatchet Mountain formation; Teanaway basalt

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.


Foster, R.J., 1960, Tertiary Geology of a Portion of the Central Cascade Mountains, Washington: Geological Society of America Bulletin v. 71, no. 2, p. 99-126.

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.

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.

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.

NGMDB product
Counties Clark - Cowlitz - Kittitas - Lewis - Pacific - Skamania