Sediment Routing and Provenance of Shallow to Deep Marine Sandstones in the Late Paleozoic Oquirrh Basin, Utah

Abstract

The Oquirrh basin is a Pennsylvanian to early Permian mixed clastic and carbonate basin in northwestern Utah. The basin is the northwesternmost 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 turbidites, debrites, and hybrid flow deposits, with a general deepening from basin initiation to the early Permian; however, the tectonic drivers and sediment source(s) for the basin are poorly constrained. To better understand the subsidence and tectonic history of the Oquirrh basin, tectonic subsidence analysis was performed on 10 published stratigraphic sections across the basin. Two phases of tectonism are interpreted to have occurred 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 the Antler Overlap basins of northeastern Nevada. Unlike other ARM basins, no basin-bounding fault or highland has been identified. To test links between sediment provenance and tectonism, 26 thin-sections were analyzed from 8 locations in a northwest to southeast transect across the basin. Gazzi-Dickinson point counting was used to determine composition and provenance. Samples fell into three mature compositional categories: quartz arenite, sublitharenite, and quartz wacke indicating cratonic interior and recycled orogenic provenances. Petrographic analysis of middle Pennsylvanian sediments revealed very well sorted, finergrained sandstones in the southeast and northwest parts of the basin versus moderately well sorted, coarser-grained sandstones in the basin center. Permian sediments have decreasing sorting and increasing variability in grain size toward the southeast. Published paleocurrent data indicate a prevailing iii southward ocean current suggesting sediment derivation and transport from the Laurentian craton to the north throughout. U-Pb ages for 845 individual detrital zircon grains in six samples of shallow marine sandstones from the Oquirrh basin shed light on late Paleozoic sediment dispersal across Laurentia. Zircon age populations resemble that of Cordilleran passive margin basins to the north and south. Age groupings reflect derivation from Paleozoic, Neoproterozoic, and Grenvillian sources within the Appalachian orogen or its sedimentary cover. In order to facilitate transport of Grenvillian-aged zircon grains (approximately 21% of total grains), a westward flowing transcontinental river system must have existed, at times, from the Late Neoproterozoic to the Permian. The fluvial system would have taken grains from the southeastern part of Laurentia and released them into a marine environment off the coast of western Laurentia, similar to how the Amazon River transports sediments from the Andes Mountains....

Detrital Zircon Geochronologic Constraints on Patterns and Drivers of Continental‐Scale Sediment Dispersal in the Late Mississippian

“…Gehrels et al () proposed a transcontinental sediment transport model whereby sandstones in the western part of Laurentia were sourced from the Appalachian orogen through a combination of westward flowing rivers, wind systems, and ocean currents. Although the Appalachian region is widely accepted as a source for Late Paleozoic sediments (Gehrels et al, ; Xie, Cains, et al, ; Xie, O'Connor, et al, ; Alsalem et al, ; Thomas et al, ; Bidgoli et al, ; Kissock et al, ; Jones et al, ; Wang & Bidgoli, ), the details of such long distance sediment transport require further study (see discussion in Thomas, ). For example, the role of recycling of Early and Middle Paleozoic strata along the hypothetical E‐W route across Laurentia has not been fully explored.…”