A detrital zircon provenance analysis of the Goldstein Peak formation.

摘要

Uranium-lead ages calculated from detrital zircons obtained from seven samples of the metasedimentary Goldstein Peak formation, exposed at the northwest tip of the Lake Kaweah roof pendant in the western Sierra Nevada Mountains, suggest deposition during the Early Cretaceous. Statistical analysis of these ages, when combined with a cross-cutting granite dike displaying evidence of wet sediment intrusion dated at 139 +/- 1.0 Ma, suggests a maximum depositional age of 135.7 +/- 5.2 Ma. This age is unusual, as Lower Cretaceous non-marine rocks in California are extremely rare.;The Goldstein Peak formation is a ∼2.5-km thick package of fluvially- and alluvial fan-deposited metasandstones and metaconglomerates. Statistical comparisons of zircon populations using overlap, similarity, and Kolmogorov-Smirnoff (K-S) tests indicate that the drainage patterns within the Goldstein Peak basin must have changed during deposition of this formation. Detrital zircon data suggest that the elastic protoliths were derived from the volcanic arc carapace from the exhumed Sierra Nevada batholith and from metasedimentary wall rocks surrounding Mesozoic plutons. Determining whether all of the pre-Mesozoic zircons could have been derived from the metamorphic framework of the batholith, or whether Goldstein Peak rivers also sourced the Mesozoic foreland basin, must wait until the detrital zircon populations of the Triassic-Jurassic Kings Sequence and other roof pendants in the Sierra Nevada are better characterized. Statistical comparisons to coeval samples of the Great Valley Group, a suite of siliciclastic rocks deposited in the Sierra Nevada forearc basin, are consistent with the hypothesis that rivers similar to those that deposited the Early Cretaceous Goldstein Peak sediments also transported sediments to the Great Valley Group.