--> --> Abstract: Northward Displacements of Forearc Slivers in the Coast Ranges of California and Southwest Oregon During the Late Mesozoic and Early Cenozoic, by A. S. Jayko and M. C. Blake, Jr.; #90992 (1993).

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JAYKO, A. S., and M. C. BLAKE, JR., U.S. Geological Survey, Menlo Park, CA

ABSTRACT: Northward Displacements of Forearc Slivers in the Coast Ranges of California and Southwest Oregon During the Late Mesozoic and Early Cenozoic

North American-Farallon-Kula plate motion data, combined with estimated strike-slip displacements obtained from the obliquity of convergence along active circum-Pacific subduction zones, can be used to estimate the amount of strike-slip displacement along the forearc region of western North America. This evidence suggests a minimum of 500 km and maximum of 1600 km displacement with respect to the Farallon plate, and a minimum of 1600 km and a maximum of 4900 km with respect to the Kula plate (or some equivalent) from the Late Jurassic to the middle Eocene (145-43 Ma).

These displacements are consistent with pre-middle Eocene displacements of paleoforearc strata (Franciscan Complex, Great Valley sequence, and related units) inferred from paleomagnetic, petrologic, stratigraphic, and pebble conglomerate data.

Tentative restorations suggest that the Elk outlier and Snow Camp terrane of southwest Oregon have affinities with the southern Klamath Mountains of northern California; that the Gold Beach terrane of southwest Oregon has affinities with central or southern California; that the Healdsburg terrane of the San Francisco area has affinities with central or southern California; and that the Nacimiento block has affinities with the Peninsular Ranges or Vizcaino area of Baja California. These tentative correlations suggest about 600-1000 km of right-lateral displacement between the Early Cretaceous and the middle Eocene which can be accommodated entirely by Farallon plate motions and/or represent minimal displacement with respect to Kula plate motions (or some equivalent).

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.