U-Pb ages of detrital zircons in Jurassic eolian and associated sandstones of the Colorado Plateau: Evidence for transcontinental dispersal and intraregional recycling of sediment

Abstract

U-Pb ages for 1655 individual detrital zircon grains in 18 samples of eolian and associated marine and fluvial sandstones of the Glen Canyon and San Rafael Groups from the Colorado Plateau and contiguous areas shed light on patterns of Jurassic sediment dispersal within Laurentia. Most detrital zircon grains in Jurassic eolianites were derived ultimately from basement provinces older than 285 Ma in eastern and central Laurentia, rather than from rock assemblages of the nearby Cordilleran margin. The most prominent peaks of constituent age populations at 420 Ma, 615 Ma, 1055 Ma, and 1160 Ma reflect derivation from Paleozoic, Neoproterozoic, and Grenvillian sources within the Appalachian orogen or its sedimentary cover. Sediment was transported to a position upwind to the north of the Colorado Plateau by a transcontinental paleoriver system with headwaters in the central to southern Appalachian region, but subordinate non-Appalachian detritus was contributed by both northern and southern tributaries during sediment transit across the continent. Subordinate detrital zircons younger than 285 Ma in selected Middle to Upper Jurassic eolianites were derived from the Permian-Triassic East Mexico and the Mesozoic Cordilleran magmatic arcs. Lower Jurassic fluvial sandstones typically contain a mixture of detrital zircons redistributed from eolian sand and derived from the East Mexico arc, which lay up-current to the southeast. Zircons in marine Curtis sandstone were largely reworked from underlying Entrada eolianite, with minor contributions from the Jurassic backarc igneous assemblage of the Great Basin. Once mature quartzose detritus was dispersed widely across southwest Laurentia by a transcontinental paleoriver system and paleowinds, which deposited extensive Jurassic ergs, durable zircon grains were recycled by multiple intraregional depositional systems. Lower Jurassic fluvial sand is locally composed, however, of detritus derived from the nearby Cordilleran magmatic arc assemblage and its Precambrian basement.