Stratigraphic Context of the Early Cretaceous Goldstein Peak Unit, West-Central Sierra Nevada Batholith, California

D. Clemens-Knott and M. W. Martin
California State University, Fullerton, CA, [email protected], [email protected]

The newly recognized Goldstein Peak (GP) unit is among the oldest of the non-marine sedimentary rock sequences in California. Preserved within the metamorphic framework of the west-central Sierra Nevada batholith, the steeply dipping GP is in depositional contact with the Jura-Triassic marine Kings Sequence to the east and the Kings-Kaweah ophiolite outcrops to the west in the San Joaquin Valley. The GP’s Early Cretaceous (Valanginian) depositional age is constrained by a single concordant U-Pb zircon date of 139±1 Ma from a granite dike that displays contact relations indicative of wet-sediment intrusion.

The ≈3-km-thick Goldstein Peak unit is composed of fluvial, alluvial fan, and lacustrine (?) clastic sediments, interrupted by a lens of subaqueous to subaerial, basaltic to dacitic pyroclastic rocks. Hornblende-hornfels facies recrystallization of mud-rich protoliths was complete, producing sillimanite-quartz-biotite schists at ≈115 Ma. The original mineralogy and depositional structures in the quartz-rich sedimentary and basaltic volcanic horizons, however, are well preserved.

The earliest Cretaceous period in central California is characterized by the marine sedimentation of the Great Valley Group (Surpless et al., 2006). These authors interpret the pre-Mesozoic detrital zircon record as indicating an original sedimentological tie between the Great Valley forearc and North America. We propose that the GP conglomerates represent less mature correlative units to the Early Cretaceous Great Valley marine sediments. On-going analysis of detrital zircon populations from a suite of GP conglomerate samples will better constrain the depositional age of this unusual non-marine formation and clarify its relation to the Great Valley forearc sequence. Moreover, a coupled geochronologic-petrographic provenance analysis should provide new information about the emergence of the Cretaceous continental margin arc.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009