The Upper Devonian (Famennian) Cove Fort Quartzite and associated strata of western Utah comprise three stratigraphic sequences, each containing a thick (<65m) forced-regression systems tract that is restricted to a narrow (<30km wide) strike belt directly west of the Cordilleran Hingeline, which forms the eastern margin of the Pilot basin. Coarse-grained shoreface quartz arenite and lagoonal dolomicrite of the Cove Fort Quartzite display the following features characteristic of the forced-regression systems tract: 1) in their proximal portions they overlie a sharp, erosional surface (sequence-bounding unconformity) that cuts into fine-grained distal-marine carbonate facies and becomes more gradational or conformable seaward; 2) they lie seaward of a zone of sedimentary bypass, and are detached and separated from the previous highstand shoreface; 3) they are confined to a relatively narrow zone less than 30km in width; 4) they are onlapped and overlain by transgressive systems tract deposits consisting of deep subtidal carbonates (West Range Limestone); and 5) the sequence-bounding unconformity beneath the forced-regression systems tract merges with a transgressive surface of erosion above the forced-regression systems tract landward of the lowstand shoreline pinch-out. We infer that high subsidence rates directly west of the Cordilleran Hingeline controlled the location and thickness of these forced-regression systems tracts and moreover resulted in vertical stacking of prime reservoir facies through time.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas