Geology Reference
In-Depth Information
of sediments as well as the depositional environment in
the middle to late Eocene. By late Eocene time rivers
feeding the basin had matured extending their water-
sheds well beyond the Klamaths into the interior of
Idaho. White micas and potassium feldspar minerals
that make up the Tyee Formation are identical to
minerals of the Idaho batholith. In the southern part of
the basin, sands transported by rivers created deltas
and shallow marine sandbars on the shelf before
cascading into the deeper basin where they were
carried on turbidity currents to form Tyee submarine
fans. The meager fossil record of this interval is due to
overwhelming amounts of sand and silt diluting the
marine faunas. In localized areas Tyee, Elkton, and
Bateman deposits accumulated up to a mile in thick-
ness. Approximately 1,500 feet of Bateman sediments
typify a shallow delta in the Tyee seas, while the 2,500
feet of Elkton sands with abundant, shallow water
molluscs and microfossils were the last to fill the
southern basin.
Roseburg Formation south of Sutherlin on
Stratigraphy of the Coast Range
Interstate 5 displays deep water turbidite
(after
Correlation of Stratigraphic
deposits (photo courtesy Leslie Magoon).
Units of North America [COSUNA], 1983)
