Marine sedimentary and tuffaceous rocks (middle Miocene to upper Eocene) (ORTmst;0)

Tuffaceous and arkosic sandstone, locally fossiliferous, tuffaceous siltstone, tuff, glauconitic sandstone, minor conglomerate layers and lenses, and a few thin coal beds. Includes Scappoose Formation (Trimble, 1963; Wells and others, 1983), mudstone of Oswald West (Niem and Van Atta, 1973; Wells and others, 1983), Pittsburg Bluff Formation (see Wells and others, 1983), and Smuggler Cove and Northrup Creek formations (informal names) of Niem and Niem (1985)

State	Oregon
Name	Marine sedimentary and tuffaceous rocks (middle Miocene to upper Eocene)
Geologic age	Late Eocene to Middle Miocene
Original map label	Tmst
Primary rock type	sandstone
Secondary rock type	siltstone
Other rock types	tuff; conglomerate; coal
Lithologic constituents	Major Sedimentary > Clastic > Siltstone (Bed) Sedimentary > Clastic > Sandstone (Bed) Incidental Igneous > Volcanic (Pyroclastic, tuff) Sedimentary > Coal (Bed) Sedimentary > Clastic > Conglomerate (Bed)
Map references	Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.
Unit references	Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000. Trimble, D.E., 1963, geology of Portland, Oregon, and adjacent areas: U.S. Geological Survey Bulletin 1119, 110 p. [http://pubs.er.usgs.gov/publication/b1119] Wells, R.E., Niem, A.R., MacLeod, N.S., Snavely P.D., Jr., and Niem, W.A., 1983, Preliminary geologic map of the west half of the Vancouver (Washington-Oregon) 1ø by 2ø quadrangle: U.S. Geological Survey Open-File Report 83-591, scale 1:250,000. [http://pubs.er.usgs.gov/publication/ofr83591] Niem, A.R., and Van Atta, R.O., 1973, Cenozoic stratigraphy of northwestern Oregon and adjacent southwestern Washington, in Beaulieu, J.D., ed., Geologic field trips in northern Oregon and southern Washington: Oregon Department of Geology and Mineral Industries Bulletin 77, p. 75-132. Niem, A.R., and Niem, W.A., 1985, Oil and tgas investigation of the Astoria Basin, Clatsop and northernmost Tillamook Counties, northwest Oregon: Oregon Department of Geology and Mineral Industries Oil and Gas Investigation OGI-14, scale 1:100,000.
Geographic coverage	Clatsop - Columbia - Multnomah - Tillamook - Washington