A conspicuous seaward bulge of the middle to late Turonian shoreline of the Cretaceous seaway in northeastern Utah and southwestern Wyoming has been identified by previous authors as the Vernal delta. Strata of the Frontier Formation and the Ferron Sandstone Member of the Mancos Shale that form the Vernal delta consist largely of fluviodeltaic facies. The delta, however, is not recognizable as a locus of Turonian sedimentation; there is no substantial isopach thickness associated with it. The Vernal delta was apparently a large feature, encompassing an area of at least 6250 mi² (16,250 km²). Comparison between the depositional setting and paleogeography of northeastern Utah during the Late Cretaceous and a structurally similar present-day area on the east flank of the Andes in Colombia suggests that a feature the supposed size of the Vernal delta could not have been produced by a single river. Strata of the Vernal delta overlie the ancestral Uinta Mountain uplift, an area where Cenomanian marine shale was entirely removed by what appears to have been submarine erosion during early Turonian time. When the shoreline prograded eastward across this area during middle Turonian time, the sediment load caused the area to subside, but at a rate slower than rates of subsidence to the north and south. We hypothesize that this differential subsidence is the cause of the shoreline bulge. Although it includes deltaic facies, the Vernal delta was probably not an actual delta, but a feature produced primarily as the result of gentle tectonic moveme t of the ancestral Uinta Mountain uplift.