TECTONIC CONTROLS ON LATE CRETACEOUS SEDIMENT PROVENANCE AND STRATIGRAPHIC ARCHITECTURE IN THE BOOK CLIFFS, UTAH

Middle–late Campanian strata of the Book Cliffs, Utah archive three clastic wedges of the North American Cordilleran foreland basin deposited east of the Sevier thrust belt. Variations in stratal architecture and provenance in these wedges provide an opportunity to evaluate controls on foreland basin deposition. There is an increase in eastward progradation rate between the Lower and Upper Castlegate Sandstone followed by a decreased progradation rate in the overlying Bluecastle Tongue and Price River formations. Detrital zircon mixture modeling indicates contributions dominated by a single source in the Sevier thrust-belt during deposition of the slowly prograding lower clastic wedge. This changes to a mixture of thrust-belt, northern, and southern source areas in the rapidly prograding middle wedge. Mixture modeling shows a return to a single dominant southern source during deposition of the overlying (third), slowly prograding clastic wedge. The introduction of multiple sources during rapid progradation is likely due to a northward propagation of exhumation in the Utah thrust-belt, culminating with exhumation in the Charleston-Nebo Salient and Uinta Uplift north of the Book Cliffs, coeval with introduction of axially-sourced detritus in the distal foreland basin. 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 along-strike sources. The return to slower progradation is coeval with a decrease in thrust-belt derived detritus and transition to a dominant southern-source contribution. Transition to a dominantly axial fluvial system during deposition of the third clastic wedge is consistent with a northeastward migration of the regional depocenter and exhumation to the south of the Book Cliffs. 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.