Alsea Formation (Oligocene and upper Eocene) (ORTa;0)

Massive to thick-bedded tuffaceous marine siltstone and fine-grained sandstone; locally concretionary. Foraminiferal assemblages assigned to the Zemorrian and upper Refugian Stages (Kleinpell, 1938; Rau, 1975) and molluscan fauna assigned (Snavely and others, 1976a) to the Lincoln and lower Blakeley Stages of Weaver and others (1944)

State	Oregon
Name	Alsea Formation (Oligocene and upper Eocene)
Geologic age	Late Eocene to Oligocene
Original map label	Ta
Primary rock type	siltstone
Secondary rock type	sandstone
Other rock types
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Bed)tuffaceous; locally concretionary Sedimentary > Clastic > Siltstone (Bed)tuffaceous; locally concretionary
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.
Geographic coverage	Jefferson - Lane - Lincoln