ABSTRACT: California Coast Range Ophiolite: Jurassic Tectonic History
HOPSON, CLIFFORD A., J. M. MATTINSON, B. P. LUYENDYK, and W. BEEBE, University of California at Santa Barbara, Santa Barbara, CA, E. A. PESSAGNO, JR., and D. M. HULL, University of Texas at Dallas, Dallas, TX, and C. D. BLOME, U.S. Geological Survey, Menlo Park, CA
The ophiolite (remnants at Point Sal, Stanley Mountain, Cuesta Ridge, Llanada) formed in the Middle Jurassic (>160-170 Ma) at an oceanic spreading rift system, at equatorial paleolatitudes, in an open-ocean setting with pelagic carbonate interlava sedimentation. Sea-floor spreading then carried this oceanic lithosphere progressively through (1) a deep-water region of starved pelagic sedimentation (late Callovian-Oxfordian depositional hiatus), (2) the tephra fringe and clastic depositional apron of an active volcanic arc where andesitic/silicic volcanogenic detritus, intermingled with radiolarian ooze (the middle Oxfordian-Tithonian volcanopelagic succession), accumulated on the deep ocean floor, (3) burial of volcanopelagic succession by muds and distal turbidites of a terrigenous fan system (upper Tithonian basal part of Great Valley Supergroup) that advances across the deep sea floor. Also during the Oxfordian-Tithonian, rapid (15-20 cm/yr) northward translation carried the oceanic lithosphere through central and northern Tethyan faunal provinces into southern Boreal Province (>30 degrees N). There, during the Late Jurassic, basaltic to silicic magmatism took place beneath the deep sea floor. This event is marked by basaltic to silicic sills (at Cuesta Ridge, Llanada, Del Puerto) that intrude the ophiolite and its volcanopelagic sedimentary cover. The Late Jurassic magmatism is ascribed to rift-tip propagation of a new ocean-ridge rift system through older oceanic lithosphere (the Middle Jurassic ophiolite). These events preceded fore-arc basin development.
AAPG Search and Discovery Article #91016©1992 AAPG-SEPM-SEG-EMD Pacific Section Meeting, Sacramento, California, April 27-May 1, 1992 (2009)