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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 57 (1973)

Issue: 2. (February)

First Page: 433

Last Page: 433

Title: Late Cenozoic Stratigraphy and Structure of Oregon Continental Margin in Framework of Plate Tectonics: ABSTRACT

Author(s): G. A. Fowler, L. D. Kulm

Article Type: Meeting abstract

Abstract:

More than 8,000 km of seismic-reflection survey and 250 rock samples provide the basis for a discussion of late Cenozoic stratigraphy and structure of the Oregon continental margin, a critical boundary region between the North American plate and the Gorda-Juan de Fuca plate. Uplifted and faulted folds along the edge of the shelf, commonly manifested as banks, are dominant shallow structural features of the margin. A persistent, broad, relatively shallow syncline lies between the banks and the shore. The continental slope off southern Oregon is characterized by a major fault and fold system; benches result from the ponding of sediments behind anticlinal folds. The northern slope consists of a series of broad anticlinal folds and intervening synclinal basins with deeper und rlying folded structure. Structural elements on the margin generally trend north-south and are either parallel or subparallel with it.

At least two regional unconformities establish a first-order subdivision of the stratigraphic column. The older separates late Miocene diatomaceous sediments from underlying rocks. The younger is Pliocene-Pleistocene. These unconformities appear to correlate with significant plate tectonic events. Second-order subdivision into stratigraphic units on the basis of gross lithologic and faunal trends, reflection characteristics, and stratigraphic succession indicates similarities to the Pullen, Eel River, and Rio Dell Formations of northern California. Generally rich foraminiferal faunas display affinities to the late Miocene to Pleistocene biostratigraphy of California.

Provenance and paleoenvironment of lower slope samples suggest a north component of motion for the Gorda-Juan du Fuca plate. Paleoenvironmental analyses indicate a total range of vertical tectonic movement since the late Miocene of approximately 1,200 m.

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Copyright 1997 American Association of Petroleum Geologists