The Role of Salt Diapirism in Controlling the Development of Dryland Fluvial Systems: A Case Study from the Permian Cutler Group, SE Utah, USA
The growth of salt diapirs and the resultant generation of surface topography can significantly impact fluvial system style and thereby exert a prime control on resultant preserved stratigraphic architecture. This study examines the response of the fluvial succession of the Permian Cutler Group to salt-walled mini-basin evolution and salt-pillow anticline development in the Paradox Basin of SE Utah.
Detailed facies and architectural analyses have been used to constrain the complex fluvial stratigraphic architecture of the Cutler Group in the mini-basin depocenters, where the succession is characterized by stacked, multi-story and multi-lateral fluvial channel complexes. Sheet-like overbank and single-story channel elements are dominant in areas immediately adjacent to salt walls, where at least two local unconformities are present.
Paleocurrent data demonstrate early fluvial progradation towards the southwest- similar to the regional drainage pattern emanating from the sediment source area of the Uncompahgre Uplift. In the area of salt mini-basin development, outcrop and well-log dip-meter data demonstrate a change in dominant fluvial flow direction towards the northwest during the middle stages of fluvial system accumulation. This records diversion of fluvial systems in response to uplift along the salt walls. Paleocurrent data from the uppermost part of the succession demonstrates a reversion to a south-westerly-directed fluvial drainage pattern and it is likely that successive infilling of mini-basins resulted in breaching of the salt highs and a re-establishment of the regional drainage pattern. Fluvially reworked gypsum clasts potentially derived from salt walls that breached the surface are only observed in the far south of the salt mini-basin area. This suggests that rates of sedimentation typically outpaced rates of salt wall growth, with only subtle surface topography acting to control fluvial pathways for the majority of Cutler Group times. To the west of the salt-walled mini-basin area, the Cutler Group thins over the salt-pillow-cored Cane Creek Anticline and subtle stratigraphic relationships demonstrate significant reworking of previously deposited sediment.
Tectono-stratigraphic models developed from this study are being applied as analogs for the characterization of fluvial reservoirs developed in salt-walled mini-basin provinces, particularly those where linear salt walls are aligned perpendicular to prevailing fluvial flow direction.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California