44 Ophiolites, Batholiths, and Regional Geology II: A Session in Honor of Cliff Hopson
Sunday, 1 May 2005
1:00 PM - 5:00 PM
GEOCHRONOLOGIC CONSTRAINTS ON EARLY CRETACEOUS DEPOSITION OF NONMARINE SEDIMENTS AND VOLCANICS, AND SYNPLUTONIC DEFORMATION, WESTERN SIERRA NEVADA BATHOLITH, CA
Paper number: 44-9
Program: SYMPOSIA SESSIONS
Time: 3:40 PM – 4:00 PM
Authors
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Jason B. SaleebyCalifornia Institute Technology, Pasadena, CA
Abstract
New mapping suggests that the Goldstein Peak protoliths were deposited on top of the siliciclastic-carbonate Lake Kaweah pendant. A minimum age for these Kings sequence rocks is provided by a 163±1.5 Ma quartz diorite intrusion. The Goldstein Peak-Lake Kaweah depositional contact has been significantly modified by sinistral shear along the 116±2 Ma, NNE-trending Stone Corral Shear Zone (SCSZ) and by syntectonic intrusion of pyroxene- and hornblende-rich gabbroids. A 112.5±1 Ma granodiorite truncates the northern end of the SCSZ. This pluton postdates the two, 123-to-115 Ma ring dike complexes of the Stokes Mountain region and coincides with an Ar-Ar date of 112.31 Ma, together marking the cessation of significant local magmatism and cooling from hornblende-hornfels facies peak metamorphic conditions.
Rocks of the Goldstein Peak pendant fill a gap in the geologic history of the western batholith south of the Fresno embayment (see Clemens-Knott et al., 2000 for references therein). The 163 Ma quartz diorite belongs to a Middle Jurassic mafic suite, interpreted as the roots of arc volcanoes intruded into the Foothills ophiolite belt. During the Late Jurassic Nevadan orogeny, a transtensional-transpressional zone cut the arc and was intruded by 155-to-148 Ma gabbroic-and-tonalitic, dikes of Owens Mountain. The onset of continental arc magmatism is recorded by 123-to-115 Ma mafic cumulates and ring dikes of Stokes Mountain. Rocks of the Goldstein Peak pendant, therefore, offer a partial record of nonmarine sedimentation, volcanism and magmatism that occurred during the 25-million-year-long period between local manifestation of the Nevadan orogeny and emergence of the Cretaceous arc.