Abstract

U-Pb ages for individual detrital zircons in sandstone record the ages of igneous source rocks in which zircon and accompanying quartz crystals formed because zircon U-Pb ages are not reset by sedimentary or diagenetic processes. Ages of detrital zircons reflect ultimate sand sources in basement rocks but allowance must be made in provenance interpretations for potential recycling of resistant zircon grains from more proximate sources in sedimentary assemblages. Our database for Mesozoic strata in south-central Utah includes 1896 concordant or nearly concordant U-Pb ages of detrital zircons from 20 samples (Triassic to Cretaceous). Upper Triassic Chinle channel sandstones were derived largely from the Ouachita orogen, uplifted on the northern shoulder of the pre-Gulf of Mexico rift system, from which Ouachita-derived sand was carried westward by paleoriver systems ~1500 km long. Eolian dune sands of Early to Middle Jurassic Glen Canyon and San Rafael ergs were derived largely from pre-Atlantic rift highlands along the Appalachian belt, transported to deltas or floodplains in the northern Rocky Mountains region by a transcontinental paleoriver system ~2000 km long carrying Appalachian-derived sediment, and delivered southward into the Colorado Plateau ergs by the paleowinds recorded by dune crossbedding. Fluvial sands of the Upper Jurassic Morrison Formation were largely reworked from older Jurassic eolianites exposed by uplift along the Sevier thrust belt or its orogen-flank precursors. Cretaceous fluvial and fluviodeltaic sands were in part recycled from Jurassic eolianites and older strata exposed along the Sevier thrust belt by transverse delivery of sediment to the Cordilleran foreland basin, and in part delivered longitudinally to the foreland basin from Precambrian basement and its sedimentary or volcanic cover exposed along the Mogollon paleohighlands lying south of the foreland basin.