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Provenance and Architectural Analysis of Linked Fluvial and Marginal Marine Depositional Systems, Cretaceous Kaiparowits Basin, Southern Utah, USA: Insights From Detrital Zircon U/Pb Geochronology and Paleomorphodynamics


New U/Pb detrital zircon geochronologic data from the Straight Cliffs Formation of southern Utah provide insight into the controls on stratigraphic architecture of the Western Interior basin during Coniacian-Santonian time. Detrital zircon ages (N=40, n=3468) derived from linked fluvial and shallow marine depositional systems throughout the Kaiparowits Plateau indicate the majority of fluvial sediment was derived from the Mogollon highlands (67%), with subordinate contributions delivered from the Sevier thrust belt (17%) and Cordilleran volcanic sources (16%). The proportion of Sevier detritus increases up-section from 18% in basal fluvial samples to 27% in uppermost strata. Shallow marine samples contain Mogollon (44%), volcanic arc (14%), and a relative increase of Sevier thrust belt-derived sediment (42%), which was delivered via longshore currents into southern Utah. Straight Cliffs Formation deposition was influenced by the development of topography in the Sevier fold and thrust belt, but to date, little emphasis has been placed on the tectonic development of the Mogollon highlands of central Arizona. In fluvial facies of the middle to upper John Henry Member, up-section increases in average grain size, channel amalgamation trends, and a north to northeastward progradation of distributive fluvial system (DFS) signal a major influx of sediment from the actively uplifting Mogollon highlands and Maria thrust belt. Fluvial strata record sediment transport parallel to the Sevier foreland basin and perpendicular to the Maria thrust belt, implying the presence of a transverse distributive fluvial system draining the Maria thrust belt. The axial drainage can be tracked to the northern Kaiparowits plateau, eventually forming a compound incised valley system. Spatial and temporal trends in alluvial architecture and continuous sediment input from the Mogollon highlands are also consistent with predictions made by models for distributive fluvial systems. The northeast-flowing axial fluvial system responsible for deposition of fluvial strata in the Straight Cliffs Formation was primarily fed by DFSs draining the Mogollon highlands, but DFSs draining the Sevier thrust belt contributed moderate volumes of sediment as well. The relative contribution of sediment from each thrust belt was likely controlled by fluctuations in subsidence rates adjacent to each thrust belt and further out in the Kaiparowits basin.