DETRITAL ZIRCON EVIDENCE FOR LINKAGES BETWEEN MESOZOIC SEDIMENTARY SYSTEMS ALONG THE WESTERN FLANK OF THE SIERRA NEVADA ARC

Detrital zircon U-Pb data from pendants in the SW Sierra Nevada batholith and from sediments exposed along the western Great Valley (all sites ~36°N latitude) document linkages between marine and nonmarine deposition along the western flank of the Mesozoic arc and the Great Valley forearc regions. Linkages are supported by statistically similar provenance data from (1) rare, fine-grained siliciclastic horizons associated with ribbon cherts and carbonates of the Early Triassic Calaveras Complex; (2) medium-grained turbiditic sandstones of the Early Jurassic Kings Sequence; (3) fluvial conglomerates and sandstones of the Early Cretaceous Goldstein Peak Formation; and (4) Early to Late Cretaceous turbidites of the Gravelly Flat formation at the base of the Great Valley Group. These Mesozoic sediments document the transition from Triassic deep marine to Jurassic arc apron to Early Cretaceous marine forearc and nonmarine intra-arc environments, and together reflect the emergence of the mid-Cretaceous continental margin arc. Similarities between Goldstein Peak fluvial deposits and lowermost Gravelly Flat forearc deposits, each comprising subequal contributions from the Mesozoic arc and pre-Mesozoic sources, support a linkage between the Early Cretaceous Goldstein Peak intra-arc basin and deposits in the nascent forearc basin. In addition, statistical similarities between the pre-Mesozoic zircon populations in the Early Cretaceous fluvial conglomerates from the western arc flank and in the forebasin to the east (Buckthorne Conglomerates; Lawton et al., 2010) suggest overall similarities between pre-arc zircon populations that were mobilized during the Early Cretaceous on both sides of the arc axis. Moreover, statistical similarities between zircon populations in Permo-Triassic sediments on both sides of the arc suggest transport of North American zircons westward across the arc axis, possibly in part by aolian transport, and tie Permo-Triassic marine sediments exposed in the western Sierra Nevada foothills to the western North American zircon system. Possible extension of the foothills metamorphic-Early Cretaceous igneous complex westward into the eastern basement of the Great Valley forearc basin would extend linkages of the eastern forearc basement to North America back to the early Mesozoic.