How Cambrian sediments mantled the Laurentian craton in southeastern California: Biomats, detrital zircon provenance, and maximum depositional age of Sauk I onset

Abstract The basal, middle member of the Wood Canyon Formation that rests on bedrock in the Marble Mountains, California, USA, occupies a key stratigraphic position and location to further decipher environmental shifts triggered by renewed sedimentation as part of the Sauk I transgression. Reexamined strata host coiled sandy rip-ups and sand-crack structures indicative of binding by terrestrial biomats in the fluvial-to-marine transition, features that are newly reported from the Wood Canyon Formation and absent from regional correlatives. The hydrodynamic conditions of the subsequent perennial braidplain were inhospitable to biomat development and preservation. Tandem detrital zircon U-Pb geochronology provides high-precision Cambrian dates that range from 539.52 ± 0.84 Ma to 525.23 ± 0.53 Ma. Ages and trace- and rare-earth–element concentrations for Cambrian zircons correspond to igneous compositions in the Arbuckle Mountains rhyolite, Wichita Igneous Province, McClure Mountain syenite, and unresolved ca. 526 Ma and ca. 534 Ma igneous sources. We report the maximum depositional age for the basal middle member of the Wood Canyon Formation as 526.39 ± 0.47 Ma, constraining initial Sauk I cover of the composite Great Unconformity to Cambrian Stage 2.