Tyee Formation (middle Eocene) (ORTt;0)

Very thick sequence of rhymically bedded, medium- to fine-grained micaceous, feldspathic, lithic, or arkosic marine sandstone and micaceous carbonaceous siltstone; contains minor interbeds of dacite tuff in upper part. Foraminiferal fauna are referred to the Ulatisian Stage (Snavely and others, 1964). Groove and flute casts indicate deposition by north-flowing turbidity currents (Snavely and others, 1964), but probable provenance of unit is southwest Idaho (Heller and others, 1985)

State	Oregon
Name	Tyee Formation (middle Eocene)
Geologic age	Middle Eocene
Original map label	Tt
Primary rock type	sandstone
Secondary rock type	siltstone
Other rock types	tuff
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Bed) Minor Sedimentary > Clastic > Siltstone (Bed) Incidental Igneous > Volcanic > Felsic-volcanic > Dacite (Pyroclastic, tuff)
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. Snavely, P.D., Jr., Wagner, H.C., and McLeod, N.S., 1964, Rhythmic-bedded eugeosynclinal deposits of the Tyee Formation, Oregon Coast Range: Kansas Geological Survey Bulletin 169, p. 461-480. Heller, P.L., Peterman, Z.E., O'Neil, J.R., and Shafiqullah, M., 1985, Isotopic provenance of the sandstones of the Eocene Tyee Formation, Oregon Coast Range: Geological Society of America Bulletin, v. 96, p. 770-780.
Geographic coverage	Benton - Coos - Curry - Douglas - Lane - Lincoln - Polk - Tillamook - Yamhill