DETRITAL ZIRCON PROVENANCE ANALYSIS OF THE GREAT VALLEY GROUP, SACRAMENTO VALLEY, CALIFORNIA

Detailed detrital zircon analysis of the Cretaceous Great Valley Group in California provides improved resolution of the history of sedimentation in the Great Valley forearc basin and the evolution of the adjacent Klamath-Sierran magmatic arc. Detrital zircon age distributions from the Sacramento Valley broaden through time from nearly unimodal age distributions to signatures with multiple age peaks. This transition to more broadly distributed detrital zircon age spectra likely results from a combination of 1) expanding subaerial drainage systems, from highly localized to more broadly distributed catchments; 2) changing shelf and submarine canyon morphology with rising sea level and/or basin subsidence; 3) increased degree of dissection of the Klamath-Sierran arc; and 4) potential drainage capture and re-direction within the arc. Sacramento Valley detrital zircon age data indicate a more complex history of drainage in the northern Klamath-Sierran arc than previously documented. This complexity likely resulted from the combined influences on arc drainage systems of Cretaceous uplift in the western arc and the dominant northwest structural trend characteristic of the northern Sierra Nevada. In addition, 150±10 Ma age zircon grains comprise a significant proportion of the Sacramento Valley detrital zircon age distributions, but have not been documented extensively in the Klamath-Sierran arc. The most likely source of these Late Jurassic to Early Cretaceous zircon grains is the now sediment-covered western flank of the Sierran block. The improved resolution of sediment provenance from detailed detrital zircon analysis of Great Valley stratigraphy enables recognition of previously undocumented arc magmatism and the evolution of regional drainage systems within the Cretaceous arc-forearc system related to uplift, magmatism, and structure in the arc.