SANDSTONE PROVENANCE IN THE LATE PALEOZOIC OQUIRRH BASIN, UTAH

The Pennsylvanian to early Permian Oquirrh Basin is the northwesternmost basin within the Ancestral Rocky Mountains (ARM) orogen. Though it is the farthest from the collision zone to the southeast, the Oquirrh had some of the fastest subsidence rates and thickest accumulation of sediment (up to 9 km) within the ARM. Unlike most other ARM basins, it does not have an identified basin-bounding fault or uplift. Additionally, subsequent deformation during the Sevier, and Basin and Range orogenies collapsed and then disaggregated the basin, making it difficult to reconstruct. Therefore, the basin is one of the least understood parts of the already enigmatic ARM orogen.

To better understand tectonic evolution and provenance of basin sediments, we combined subsidence analysis, thin section point counts, and detrital zircon U-Pb geochronology. Subsidence analysis suggests a two-phase subsidence model, with rapid subsidence in middle Pennsylvanian time in the eastern and central parts of the basin followed by a second early Permian subsidence phase in the western part of the basin. However, these subsidence pulses do not seem to affect the provenance data. Sandstones in the Oquirrh basin are compositionally mature with sparse feldspar and lithic grains, indicative of cratonic interior or recycled orogenic provenance. U-Pb ages on detrital zircons from three Pennsylvanian and three Permian samples are consistent with sample derivation from Laurentian basement provinces to the east and north. Published paleocurrent data indicate sediment transport dominantly from the north, consistent with the bulk of sediment filling the Oquirrh Basin being transported southwards from the stable Laurentian craton and Wyoming shelf located to the north and east throughout the life of the basin.