Abstract

A new stratigraphic model more clearly defines the Early Cretaceous foreland basin of the Sevier fold and thrust belt in eastern Utah and southwestern Colorado. Age relationships and stratigraphic architecture of the basin lead to a better understanding of the timing and nature of deformation in both the thrust belt and the foreland. Early Cretaceous age-diagnostic fossils indicate that subsidence and by inference, thrusting, began in Barremian to middle Albian time and ceased at or before the end of the Albian. Barremian dinosaur-bearing strata in the Salt Valley Anticline may be older than the oldest rocks in the proximal part of the foreland basin. In which case, the Dinosaur-bearing strata was probably preserved as a result of subsidence due to salt movement prior to the initiation of thrusting.

The youngest rocks occur in the proximal part of the basin, suggesting that the distal basin margin migrated toward the thrust belt and the basin got narrower as thrusting proceeded. The apparent narrowing of the basin may have been caused by a thickening of the thrust wedge.