Timing and record of foreland sedimentation during the initiation of the Sevier orogenic belt in central Utah

Abstract

AbstractThe stratigraphic record in the San Rafael Swell region of central Utah suggests that thrust loading and attendant foreland sedimentation began in adjacent parts of the Sevier orogenic belt during Albian time. Regional stratigraphy, isopachs, gravel composition and grain‐size trends suggest that the Morrison Formation of Late Jurassic age and Buckhorn Conglomerate Member of the Cedar Mountain Formation of Early Cretaceous age were not derived from the adjacent thrust belt as they neither thicken nor coarsen significantly towards the west. In contrast, the upper member of the Cedar Mountain Formation of Albian age and Dakota Sandstone of early Cenomanian age rapidly coarsen and thicken westward towards the thrust belt, suggesting that these units were deposited during a time of rapid flexural subsidence early in the history of thrust loading by the Sevier belt. Hence, in the case of the foreland basin in central Utah, basin subsidence rates and asymmetry provides the strongest evidence of the initiation of thrust‐belt loading by the adjacent Sevier orogenic belt.