A Detrital Zircon Study of the Age and Provenance of the Gravelly Flat Formation, Great Valley Group and Metasedimentary Rocks of the Tule River and Slate Mountain Pendants

Early Cretaceous fluvial sediments preserved in a metamorphic pendant on the western margin of the Sierra Nevada mountains provide the basis for reconstructing sediment transport from the Mesozoic arc westward into the nascent forearc basin. Specifically, detrital zircon dates are used to test the hypothesis that the Early Cretaceous rivers that deposited the metasedimentary Goldstein Peak formation also delivered some of the first sediment to the Great Valley forearc basin at modern-day 36°N latitude. First, zircons were separated from three samples of the Early Cretaceous(?) Gravelly Flat Formation--the stratigraphically lowest sediments of the Great Valley Group in the San Joaquin basin--in order to determine whether the 139 Ma Goldstein Peak formation and Gravelly Flat Formation are indeed approximately coeval. Second, zircons were separated from three metasedimentary samples from the Tule River and Slate Mountain pendants in order to address the provenance of any pre-Mesozoic zircons present in the Gravelly Flat Formation. Analysis of these six detrital zircon samples was performed the Arizona Laserchron Center in late September 2011. Third, statistical comparisons of the Gravelly Flat data to detrital zircon analyses of metamorphosed fluvial sediments of the Early Cretaceous Goldstein Peak formation are used to assess the degree of overlap and similarity between the fluvial and forearc sediments. In addition, the data are used to assess whether all of the detrital zircons present in the Gravelly Flat Formation could have been derived from the Mesozoic Sierra Nevada arc and its Paleozoic-Mesozoic metamorphic framework.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California