EMERGING NEW PARADIGMS IN THE PARADOX SALT BASIN, UTAH AND COLORADO

Nearly 150 years of both surface and subsurface geologic studies of the Paradox Basin in southeastern Utah and southwestern Colorado have yielded a relatively simple halokinetic history and salt basin architecture in comparison to other highly complex and dynamic salt basins around the world. The Paradox Basin has been characterized as a series of roughly symmetrical, linear salt anticlines/walls that formed in response to differential loading onto evaporite facies of the Pennsylvanian Paradox Formation by the Pennsylvanian/Permian Cutler Group fluvial deposits during Ancestral Rocky Mountains tectonism. Passive diapirism supposedly ended roughly synchronously (Cretaceous) across the basin. Cenozoic post-rise halite dissolution resulted in fault-bounded collapse and erosion of many of the salt-cored anticlines and formation of gypsum/anhydrite caprock currently exposed at the surface.

With the continuously improving seismic imaging of salt systems and voluminous well-bore datasets acquired from petroleum-producing salt basins worldwide, many new salt features have been identified. However, these features had not been recognized in the Paradox salt basin until recently. Utilizing 2D seismic lines, well logs and new detailed outcrop studies of Gypsum and Castle valleys in the Paradox Basin, we highlight several of these newly recognized salt features that indicate that the Paradox Basin is a much more complex salt system than previously thought and the timing, distribution and nature of halokinesis in the basin may warrant reevaluation. These newly recognized features include: 1) secondary salt welds that extend short distances (<.5km) laterally away from salt wall terminations; 2) counter-regional faults merging into the proximal margins of the salt walls; 3) radial faults, which extend short distances (<2km) away from the salt diapirs and are concentrated at the arcuate ends of salt walls; 4) megaflaps comprising steeply dipping panels of Pennsylvanian Honaker Trail and uppermost Paradox strata that extend 2.5 kms up the sides of the salt walls; 5) lateral carbonate caprock that formed during the Permian and Triassic and may be misidentified as the Honaker Trail Fm., and 6) shoulder-roll structures, which are anticlines over salt shoulders where the steep edges of diapirs step abruptly inward.