Structural and Stratigraphic Evolution of the Sinbad Valley Salt Wall, NE Paradox Basin, SW Colorado

Abstract

Salt walls of the Paradox Basin of Utah and Colorado have historically been interpreted as broadly symmetrical with a simple salt tectonic history. For example, the Sinbad Valley salt wall in the northeastern Paradox Basin, southwestern Colorado, has been interpreted as a simple salt anticline, but has not been studied in detail since the 1950s. However, many other salt basins (e.g., Gulf of Mexico, North Sea) have been recently shown to have more complex salt-sediment interfaces and halokinetic features. Integrating new and existing field mapping, measured sections, well data, and 2D seismic interpretation, we document previously unrecognized halokinetic features at the Sinbad Valley salt wall. These halokinetic features include a megaflap, counterregional fault, radial faults, and intrasalt conglomerate stringers. On the basis of these newly recognized features, we present a revised interpretation for the evolution of the Sinbad Valley salt wall. We suggest that early erosion of the Uncompahgre Uplift resulted in the deposition of carbonate-clast conglomerates in the proximal Paradox Formation, which were subsequently entrained in the growing Sinbad salt diapir and are now exposed in the center of Sinbad Valley. Subsequent deposition of Pennsylvanian through Permian strata was localized by a counterregional fault located over the northeastern side of the salt wall, driving salt basinward, and initiating single-flap active diapirism and eventual formation of a megaflap on the southwestern flank of Sinbad Valley diapir. Exposures of the megaflap along the length of Sinbad Valley record significant lateral changes in the thickness, structural geometry, and depositional facies, which define several structural domains that may result from early radial faulting, an undulating salt-sediment interface, or varying levels of preservation of the original diapir roof that became the megaflap. The presence of angular unconformities, growth strata, and radial faulting record continued growth of the salt wall from the Permian through the Triassic, with diapirism waning in the Cretaceous. The features described at Sinbad Valley provide outcrop analogs for hydrocarbon exploration at other salt walls within the Paradox Basin and in other salt basins worldwide, where salt-sediment interaction affects reservoir distribution, seal presence, trap timing, and drilling hazards, all of which are critical to successful exploration, appraisal, and production evaluation.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018