Tectonic Controls on Late Cretaceous Sediment Provenance and Stratigraphic Architecture in the Book Cliffs, Utah



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Middle to late Campanian strata of the Book Cliffs, Utah record the Late Cretaceous deposition of three clastic wedges in the North American Cordilleran foreland basin east of the Sevier thrust-belt. Variations in wedge geometries provide an opportunity to evaluate tectonic controls on foreland basin stratigraphic architecture. There is a significant increase in eastward progradation rate from the Lower to Upper Castlegate Sandstone, followed by a decreased progradation rate in the overlying Bluecastle Tongue and Price River Formation. Rapid progradation during deposition of the Upper Castlegate Sandstone may be caused by increased sediment supply from either rapid exhumation of the Sevier thrust-belt or introduction of a new sediment source. Alternatively, rapid progradation may be caused by a reduction in basin subsidence due to intraforeland Laramide uplifts or a change in the locus of dynamic subsidence. Temporal and spatial changes in the detrital zircon U-Pb age spectra can be attributed to changes in sediment dispersal patterns, changes in orogenic belt distribution, and/or major tectonic episodes. Mixture modeling of relative contributions from potential source areas indicates a mixed contribution of a thrust-belt, northern, and southern source during rapid progradation, followed by a change to a dominant southern source during slower progradation of the overlying strata. The introduction of multiple sources is likely due to a northward propagation of exhumation, culminating with exhumation in the Charleston-Nebo Salient and Uinta Uplift north of the Book Cliffs, coeval with introduction of southern axially-sourced detritus in the distal foreland basin. The return to slower progradation is coeval with a decrease in thrust-belt derived detritus and transition to a dominant southern-source contribution. Expansion of the axial fluvial system during this interval is consistent with a northeastward migration of the regional depocenter. Migration of subsidence and exhumation can be attributed to dynamic subsidence and uplift associated with the northeastward subduction of the Conjugate Shatksy Rise oceanic plateau beneath the Book Cliffs area. Rapid progradation observed during deposition of the Upper Castlegate Sandstone was controlled by a combination of increased sediment supply due to increased exhumation in the Sevier thrust-belt and introduction of multiple sources.



Book Cliffs, Blackhawk, Castlegate, Sego, Neslen, Bluecastle, Farrer, Zircon, Geochronology, U-Pb dating, Mixture modeling, Provenance, Sediment source, Tectonic controls, Sediment supply, Accommodation, Exhumation, Stratigraphic architecture, Progradation, Sevier thrust, Laramide orogeny, Dynamic subsidence