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Northward displacements of forearc slivers in the Coast Ranges of California and Southwest Oregon during the late Mesozoic and early Cenozoic

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Abstract

North American-Farallon-Kula plate motion data, combined with estimated strikeslip displacements obtained from the obliquity of convergence along active circumPacific 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 minumum of 500 km and maximum of 1600 km displacement with respect to the Farallon plate, and a minumum of 1600 km and a maximum of 4900 km with respect to the Kula plate (or some equivalent) from Late Jurassic to middle Eocene (145 Ma to 43 Ma). These displacements are consistent with pre-middle Eocene displacements of paleoforearc strata (Franciscan Complex, Great Valley sequence and related units), inferred from pa 1eomagnetic, petrologic, stratigraphic, and conglomerate pebble 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 southern California; that other Franciscan rocks of the San Francisco area have 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 Early Cretaceous and middle Eocene time which can be entirely accommodated by Farallon plate motions and (or) represent minimal displacement with respect to Kula plate motions (or some equivalent).

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Northward displacements of forearc slivers in the Coast Ranges of California and Southwest Oregon during the late Mesozoic and early Cenozoic
Year Published 1993
Language English
Publisher Society of Economic Paleontologists and Mineralogists
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 17 p.
Larger Work Type Book
Larger Work Subtype Monograph
Larger Work Title Mesozoic paleogeography of the Western United States
First page 19
Last page 36