DIFFERENT DETRITAL-ZIRCON CHRONOFACIES IN AEOLIAN VERSUS FLUVIAL STRATA OF THE CUTLER GROUP, COLORADO PLATEAU, USA

Spatial and temporal changes in the provenance of detrital sediment can provide important insight into the Earth system, including how sediment sources and pathways differ under different tectonic, geographic and climate regimes. Here we examine U-Pb crystallization ages of detrital zircons collected from interbedded (1) aeolian and (2) fluvial strata of the Pennsylvanian-Permian Cutler Group (Colorado Plateau, USA) interpreted to have been deposited during the growth and decay, respectively, of continental ice sheets on Gondwana during the Late Paleozoic ice age. Building upon data from similar samples previously collected nearby and stratigraphically lower, here we report new U-Pb zircon geochronology from seven sandstone samples acquired from a ~40m thick measured section of the Cutler Formation near Bride Canyon, outside Moab, Utah. The section consists of approximately eight cyclothems containing alternating: (1) orange, fine-grained, well-sorted, and planar cross-bedded aeolian sandstones; and (2) purple, coarse-grained, normally graded, and trough cross-bedded fluvial sandstones; as well as related transitional and other associated facies. The samples were collected from 2 to 8 meter thick fluvial beds and 2 to 3 meter thick aeolianite beds, whose provenance we analyzed through U-Pb laser ablation ICP-MS. Collectively, fluvial deposits interpreted to have accumulated during warmer and wetter interglacial periods are heavily dominated by ca. 1.45 Ga and 1.75 Ga zircon populations, most likely derived directly from orthogneisses in the nearby Ancestral Rocky Mountains’ Uncompahgre uplift. In contrast, aeolian strata interpreted to have been deposited during colder, drier glacial periods have smaller populations of these Mesoproterozoic and Paleoproterozoic zircons and contain substantial Paleozoic and Neoproterozoic populations originating from more distant sources, and that were likely subjected to sedimentary recycling. Together, these data indicate that sediment provenance and transport pathways vary depending upon the predominant global climate regime. Moreover, they present an opportunity to reconstruct the magnitude and directions of low-latitude aeolian sediment flux during fluctuating climate states within the Late Paleozoic icehouse.