Sedimentary rocks (Oligocene and upper Eocene) (ORTsd;0)

Marine shale siltstone, sandstone, and conglomerate, in places partly composed of tuffaceous and basaltic debris; interbeds of arkosic, glauconitic, and quartzose sandstone. Foraminifers are referable to the Refugian and Zemorrian Stages (see marine sedimentary rocks-units Toes and Toem-of Wells and others, 1983). Includes Bastendorff Formation of Baldwin (1974)

State	Oregon
Name	Sedimentary rocks (Oligocene and upper Eocene)
Geologic age	Late Eocene to Oligocene
Original map label	Tsd
Primary rock type	shale
Secondary rock type	siltstone
Other rock types	sandstone; conglomerate
Lithologic constituents	Major Sedimentary > Clastic > Siltstone (Bed) Sedimentary > Clastic > Mudstone > Shale (Bed) Minor Sedimentary > Clastic > Sandstone (Bed) Incidental 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. 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] Baldwin, E.M., 1974, Eocene stratigraphy of southwestern Oregon: Oregon Department of Geology and Mineral Industries Bulletin 83, 40 p.
Geographic coverage	Polk - Tillamook - Washington - Yamhill