Miocene nonmarine rocks

Poorly to moderately consolidated tuffaceous sandstone, conglomerate, siltstone, and claystone in western Washington. Chiefly clay and shale with minor sand, gravel, and diatomaceous earth near Spokane. Includes diatomite beds near Yakima and Quincy, and some marine beds in Western Washington.
State Washington
Name Miocene nonmarine rocks
Geologic age Late Miocene
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Minor
Sedimentary > Clastic > Mudstone > Claystone (Bed)
Incidental
Unconsolidated > Coarse-detrital (Fluvial)
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Clastic (Tuffaceous)Also referred to as ""water-laid tuff"".
Comments The various lithologic units of the Wilkes formation interfinger and grade laterally into one another, so that no one section is typical of the whole formation (Roberts, 1958). Quantity estimations below based on composite section of Wilkes Formation (Roberts, 1958), description of Latah Formation (Griggs, 1973) and description of nonmarine sedimentary rocks in Centralia-Chehalis District (Snavely and others, 1958).
Stratigraphic units Wilkes Formation; Latah Formation; Ellensburg Formation (in small part)
References

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.

Weis, P.L., 1968, Geologic Map of the Greenacres Quadrangle, Washington and Idaho: U. S. Geologic Quadrangle Maps of the United States Map GQ-734, scale 1:62,500.

Griggs, A.B., 1973, Geologic Map of the Spokane Quadrangle, Washington, Idaho, and Montana: U. S. Geological Survey Miscellaneous Geologic Investigations Map I-768, 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.

Snavely, P.D.,Jr., Brown, R.D., Roberts, A.E., Rau, W.W., 1958, Geology and Coal Resources of the Centralia-Chelalis District, Washington: U. S. Geological Survey Bulletin 1053, 149 p.

NGMDB product
Counties Asotin - Cowlitz - Douglas - Grant - King - Kittitas - Lewis - Lincoln - Pierce - Spokane