Tectonic control of Eocene arkosic sediment deposition, Oregon and Washington
Chronostratigraphic and geographic studies of Eocene arkosic sandstones suggest deposition during a volcanically quiet interval resulting from the westward jump of the Farallon-Kula plate subduction zone in Oregon and Washington. The Eocene arkosic sandstones were deposited as part of a broad fluvial plain-coastal plain-shelf margin basin complex extending throughout Oregon and Washington between uplands of Mesozoic rocks. Feldspathic-quartzose sediments were transported from the east by river systems draining granitic terrains perhaps as far away as the Idaho Batholith. Chronostratigraphic correlations suggest that the arkosic sandstones were deposited along the margins of the depositional system during the early Eocene, prograded westward during the middle Eocene, and then regressed during the latest Eocene and Oligocene simultaneously with the influx of abundant pyroclastic debris. During the early Eocene, a northwest-southeast seamount chain was extruded on the Farallon and Kula plates west of an eastward-dipping subduction zone. Subduction of the oceanic plates moved the seamount chain obliquely toward the subduction zone. In middle Eocene time-49 to 40 m.y.b.p-the seamount chain reached the subduction zone creating instability in the subduction system and resulting in the westward jump of the underthrust boundary between the Farallon-Kula and North American plates. Coincident with and continuing after the subduction zone jump and seamount accretion, eastwardly derived arkosic sediments prograded across Oregon and Washington spilling into the new fore-arc basin and enveloping the seamounts.
- Research Organization:
- Mobil Exploration and Producing Services, Inc., Dallas, TX
- OSTI ID:
- 6307256
- Report Number(s):
- CONF-8304200-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 67:3; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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ALLUVIAL DEPOSITS
FEDERAL REGION X
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGY
IGNEOUS ROCKS
NORTH AMERICA
OREGON
PETROLEUM GEOLOGY
PLATE TECTONICS
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
TECTONICS
USA
VOLCANIC ROCKS
WASHINGTON