THE OLIGOCENE MARINE MOLLUSCAN FAUNA OF THE EUGENE FORMATION IN OREGON
Dateien
Datum
1969-08
Autor:innen
Zeitschriftentitel
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Verlag
Museum of Natural History, University of Oregon
Zusammenfassung
Tuffaceous marine sandstone and siltstone of the Oligocene Eugene Formation occur in the southern portion of the Willamette Valley in Oregon from Cottage Grove northward along the margin of the Coburg
Hills to Brownsville and Lebanon and into the Salem and Eola Hills west of Salem.
The faunal assemblages and associated rocks indicate that the Eugene Formation was deposited in
shallow water, 0-40 fathoms. The fauna contains a mixture of subtropical and temperate forms which coexisted
in what is interpreted as a gradually cooling environment. Relatively undisturbed assemblages of
infaunal pelecypods and scaphopods are common along with concentrated layers of reworked infaunal assemblages
containing a variety of epifaunal species.
The age of the fauna is believed to span portions of the lower and middle Oligocene. The fauna is partly
intermediate between the faunas of the Keasey and Pittsburg Bluff Formations in northwestern Oregon and
is considered the partial time equivalent of these formations and the missing interval between them.
The author collected several thousand fossil specimens from localities throughout the formation and
incorporated them into the collections at the University of Oregon. In addition, previous collections housed
at the University of California, California Academy of Sciences, Stanford University, and the U.S. Geological
Survey at Menlo Park, California, were examined.
Sixty-seven species, representing 48 genera and 31 families, are discussed and figured; and their affinities
and stratigraphic ranges are analyzed. Supplementary descriptions are given for previously described
species. In addition, nine new taxa are proposed and described: Nemocardium formosum, Tellina aduncanasa, Semele willamettensis, Martesia turnerae, Pandora laevis, Dentalium laneensis, Neverita thomsonae,
Bruclarkia vokesi, and Acila nehalemensis subsp. minima.
Beschreibung
124 pages
Schlagwörter
Tuffaceous, marine sandstone, siltstone, Oligocene Eugene Formation, infaunal pelecypods, scaphopods, epifaunal, Nemocardium formosum, Tellina aduncanasa, Semele willamettensis, Martesia turnerae, Pandora laevis, Dentalium laneensis, Neverita thomsonae, Bruclarkia vokesi, Acila nehalemensis, Acila nehalemensis minima