PROVENANCE ANALYSIS OF LATE CRETACEOUS SANDSTONES IN BOOKS CLIFF, UTAH

The Late Cretaceous Castlegate sandstone is bounded by the oldest and overlying, medial, coarse grained clastic wedges that prograded and are well exposed in the Book Cliffs, Utah. The overlying, middle wedge was prograded to an anomalous extent relative to the oldest and youngest wedges. Two conflicting models have been proposed for the progradation of the Castlegate sandstone as part of the evolution of the Cordilleran foreland basin during the overlapping deformation events in the Sevier fold thrust belt, and the basement-cored, intra-foreland basin uplifts of the Laramide deformation. One model invokes an increase in the exhumation rates in the Sevier fold-thrust and predicts a change in sediment composition. The second model predicts that a decrease in subsidence in the foreland basin during the Laramide deformation event will lead to a decrease in accommodation but predicts no systematic change in sediment composition. The purpose of this petrographic study is to use the Gazzi-Dickinson method for point counting to observe a shift in sandstone composition that may have occurred during the formation of the middle wedge. Preliminary petrographic data of sandstone samples collected in Price, Utah, corroborate an increase in lithic content upsection in the downward dipping direction which may be due to a change in provenance. This project is part of a larger on-going project that uses detrital zircon dating to distinguish sediment supply from accommodation.