SEDIMENT ROUTING AND PROVENANCE OF SHALLOW TO DEEP MARINE SANDSTONES IN THE LATE PALEOZOIC OQUIRRH BASIN, UTAH

The Oquirrh Basin is a Pennsylvanian to early Permian mixed clastic and carbonate basin in northwestern Utah. The basin is the northwestern-most expression of the Ancestral Rocky Mountains (ARM) orogeny, and locally contains up to 9 km of sediment. Depositional facies range from shelf carbonates to deep marine debrites, with a general deepening from basin initiation to the beginning of the Permian; however, the tectonic drivers for the basin are poorly constrained. Tectonic subsidence analysis was performed on 10 published stratigraphic sections across the basin. Two phases of tectonism are interpreted on either side of the basin, forming distinct depocenters during the middle Pennsylvanian and early Permian. Pennsylvanian subsidence is interpreted as a flexural response to a crustal load east of the basin coeval with the ARM, whereas Permian subsidence in the western part of the basin may be related to the uplift and unconformity sequence documented in northeastern Nevada. Unlike other ARM basins, no basin-bounding fault or highland has been identified.

To test links between sediment provenance and tectonism, Gazzi-Dickinson point counting and U-Pb detrital zircon geochronology were used and suggest local tectonism played only minor roles in altering dominant sedimentation patterns. Sandstone point counting showed that Oquirrh Group sandstones are compositionally mature and contain sparse feldspar or lithic grains, leading to the interpretation that sample sediments were derived from the cratonic interior or from a recycled orogenic source. Detrital zircon dating of three Pennsylvanian and three Permian samples also suggest sediment was overwhelmingly derived from multiple Laurentian basement provinces to the north and east. Published paleocurrent data indicate a prevailing southward ocean current, suggesting sediment transport from the stable Laurentian craton and Wyoming shelf to the north throughout the late Paleozoic.