Print this pageAbstracts: Magnetic
Stratigraphy
of the Eocene-Oligocene Lincoln Creek Formation, Porter Bluffs,
Washington
ARMENTROUT, JOHN M., DONALD R. PROTHERO and CHRISTOPHER D. JAQUETTE
The Lincoln Creek
Formation at Porter Bluffs, Washington, contains an important sequence
of late Eocene-Oligocene strata containing foraminifera and molluscs, and
is the type section of the Echinophoria fax molluscan zone of Armentrout
(1973, 1975). Under thermal and alternating field demagnetization, and
stable magnetic component was obtained which passes a reversal test, and
shows little tectonic rotation or translation (given the large error estimates).
Magnetic stratigraphy
shows that the Porter Bluffs section consists of
three unconformity-bounded packages. The lowest contains the upper E. dalli
zone, which correlates with late Eocene Chron C13r (about 34 to 34.5 Ma).
The second, which consists of most of the type E. fax zone, apparently
correlates with early Oligocene Chrons C13n and early Chron C12r (33.7-32.7
Ma). The third, which includes part of the E. rex zone, correlates with
early Oligocene Chron C12n (30.5-30.8 Ma). Apparently unconformities removed
strata representing the lower E. fax zone and the Eocene-Oligocene boundary
(33.5-34.0 Ma), and also the lower E rex zone (30.9-32.9 Ma).
Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California