GEOCHRONOLOGIC CONSTRAINTS ON EARLY CRETACEOUS DEPOSITION OF NONMARINE SEDIMENTS AND VOLCANICS, AND SYNPLUTONIC DEFORMATION, WESTERN SIERRA NEVADA BATHOLITH, CA

New U-Pb zircon dating of the Goldstein Peak pendant confirms its Early Cretaceous age (Valanginian), making it the oldest nonmarine volcano-sedimentary section in the metamorphic framework of the western central Sierra Nevada batholith. The 2-km-thick pendant is composed of fluvial-alluvial fan-lacustrine (?) clastic sediments, interrupted by a lens of subaqueous to subaerial, basaltic to dacitic pyroclastic rocks. A minimum age for the sediments overlying the volcanic lens is provided by a suite of 139±1 Ma garnet granite dikes that display contact relations indicative of wet-sediment intrusion.

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.