Pliocene nonmarine rocks

Conglomerate, sandstone, shale, and mudstone. Tuffaceous in part; contains alluvial fan type material locally.
State Washington
Name Pliocene nonmarine rocks
Geologic age Pliocene
Lithologic constituents
Major
Sedimentary > Clastic > Conglomerate (Bed)
Minor
Sedimentary > Clastic > Sandstone (Tuffaceous)
Sedimentary > Clastic > Sandstone > Arkose (Bed)
Sedimentary > Clastic > Sandstone > Graywacke (Bed)Lithic sandstone?""
Incidental
Unconsolidated (Alluvial, Mass wasting)
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Comments Walsh and others, 1987, describe this unit as "gravel, sand, silt, and clay"; Phillips, 1987, (referenced by Walsh and others, 1987) describes the Troutdale Formation as "vitric sand and quartzite-bearing gravel, fine-grained leaf-bearing sand, silt, clay, micaceous quartzose sand, and cobbly and bouldery vitric sand" with a volcanic breccia subunit. These descriptions are inconsistant in form (sediments versus sedimentary rocks) but not material with the detailed Tolan and Beeson, 1984, description. The lithology below is based on the Tolan and Beeson, 1984, description.
Stratigraphic units Troutdale Formation
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.

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.

Tolan, T.L. and Beeson, M.H., 1984, Intracanyon flows of the Columbia River Basalt Group in the lower Columbia River Gorge and their relationship to the Troutdale Formation: Geological Society of America Bulletin, v. 95, no. 4, p. 463-477.

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 - Skamania