Halokinetic Features in the Paradox Basin, Utah and Colorado

Abstract

Halokinetic features adjacent to the salt-sediment interface record key information about the evolution of salt diapirs and their associated minibasins. Recent work, primarily at Gypsum and Castle valleys in the Paradox Basin, has identified a number of newly recognized and reinterpreted halokinetic features adjacent to the salt walls, including megaflaps, counterregional faults, salt shoulders, radial faults, secondary welds, drop-in minibasins, and lateral caprock. Using previously published maps, new mapping, and measured sections, as well as subsurface interpretations of well logs and 2D seismic data, we evaluated all of the salt walls and associated minibasins in the Paradox Basin. Our results suggest that these features are preferentially present at certain locations along the length of the various salt walls. For example, megaflaps, documented at Moab, Gypsum, Sinbad, and Fisher valley salt walls, occur along the southwestern (distal) flanks of the salt walls. Counterregional and radial faults are the most common salt wall terminations, at the narrow ends of the walls, and are documented on at least one termination at all salt walls. Our interpretations of adjacent minibasins suggest that the timing and geometries vary across the basin and influence the formation and timing of the halokinetic features. In the northeastern part of the basin, proximal to the Uncompahgre Uplift, a prograding sediment wedge of Pennsylvanian through the Permian strata drove salt withdrawal bounded by northeast-dipping counterregional faults, initiating the formation of the salt walls. Farther southwest in the basin, asymmetric minibasins were formed by the migration of depocenters/pathways in response to salt movement and depositional loading throughout the Permo-Triassic. The formation of megaflaps, salt shoulders, and lateral caprock is related to the timing and location of the depocenters, counterregional faults, and regional unconformities. The lack of secondary welds across the basin supports previous interpretations of minor regional shortening, and therefore the megaflaps most likely formed by halokinetic drape folding. These results have important implications for hydrocarbon exploration, development, and production in salt basins, including improving our understanding of subseismic salt-sediment geometries for trap, reservoir, and seal prediction, identification of potential drilling hazards, and reducing uncertainty in resource estimates.

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