Geochemistry of the Great Valley Group: an integrated provenance record

Sedimentary geochemistry of fine-grained strata of the Great Valley Group (GVG) in California documents a provenance signal that may better represent unstable, mafic minerals and volcanic clasts within sediment source regions than the provenance signal documented in the petrofacies and detrital zircon analysis of coarser sedimentary fractions. Geochemistry of the GVG provides an overall provenance framework within which to interpret sandstone petrofacies and detrital zircon age signatures. The geochemical signature for all Sacramento Valley samples records an overall continental arc source, with significant variation but no clear spatial or temporal trends, indicating that the geochemical provenance signal remained relatively consistent and homogenized through deposition of Sacramento basin strata. The San Joaquin basin records a distinct geochemical provenance signature that shifted from Early to Late Cretaceous time, with Lower Cretaceous strata recording the most mafic trace element geochemical signature of any GVG samples, and Upper Cretaceous strata recording the most felsic geochemical signature. These provenance results suggest that the early San Joaquin basin received sediment from the southern Sierran foothills terranes and intruding plutons during the Early Cretaceous, with sediment sources shifting east as the southern Sierran batholith was exhumed and more deeply eroded during the Late Cretaceous. The GVG provenance record does not require sediment sources inboard of the arc at any time during GVG deposition, and even earliest Cretaceous drainage systems may not have traversed the arc to link the continental interior with the margin. Because the GVG provenance signature is entirely compatible with sediment sources within the Klamath Mountains, the northern and western Sierran foothills belt, and the main Cretaceous Sierran batholith, the Klamath-Sierran magmatic arc may have formed a high-standing topographic barrier throughout the Cretaceous period.