Upper Cretaceous Ferron-Frontier Clastic Wedge, Utah and Wyoming--Interplay Between Sea Level, Sediment Supply, and Subsidence: ABSTRACT

The Ferron-Frontier clastic wedge is among the most widespread in the Cretaceous System of North America. Some writers have emphasized the role of eustatic sea level in forming this clastic wedge; others have emphasized tectonics and variations in sediment supply. The evidence indicates that both were important, but to varying degrees and at different times. The Greenhorn regression was rapid, spanning only the middle part of Turonian time. It was caused primarily by lowering of sea level. Vast tracts of the sea floor that had previously been below wave base shoaled and became areas of accumulation of sandy and/or bioclastic-rich sediments. Sea level began to rise during late Turonian time. Subwave-base conditions returned to much of the sea floor, and the shoreline transgressed westward. It was during the Niobrara trangression that uplift in the Sevier orogenic belt and within the western part of the foreland basin caused a large volume of sediment to be carried eastward through the Ferron-Frontier river systems. In southwestern Wyoming, the influx of sediment slowed the transgression and resulted in stacking of shoreline sandstone units. The influx of sediment in central Utah was even greater - so much so that the shoreline once again prograded seaward.more » Late Turonian time marked the peak regression of the shoreline in that area. The tectonically induced influx of sediment appears to have been short-lived. A continued rise of sea level, combined with renewed downwarping of the foreland basin and trapping of sediment within it, led to abrupt westward transgression of the shoreline during Coniacian time.« less