Three-dimensional modeling of complex salt wall terminations in the Paradox Basin: implications for salt structure evolution, compartmentalizing fault trends and petroleum exploration

Abstract

The Paradox Basin, located in southeastern Utah and southwestern Colorado, is a stunning geologic area for salt tectonics research. Characterized by the halite-rich Pennsylvanian Paradox Formation, this region provides pristine examples of the many structural and stratigraphic relationships associated with evolving salt structures. Formed during the Ancestral Rocky Mountain orogeny (ARM), the basin displays the complex development of the Colorado Plateau throughout the past ~320-300 million years. Unlike other ARM basins, the Paradox Basin was substantially influenced by the dynamic evolution of the Paradox Formation. The northwest-southeast-striking salt structures in the Paradox Basin exhibit unusual morphologies, which has been attributed to compartmentalization of the basin by northeast-southwest-trending Precambrian basement structures. This has resulted in the abrupt or abnormal terminations of these salt structures observed in the basin today. Previously, minimal research was conducted on these salt wall terminations, perhaps due to their complex, three-dimensional geometries. However, study of these salt wall terminations is essential to understanding the evolution of the salt walls and the adjacent stratigraphy. Three-dimensional modeling of the Castle Valley and Gypsum Valley salt wall terminations reveals: (1) pre-existing Precambrian basement structures directly influenced the flow of the Paradox salt, generating the unusual salt wall terminations in the Paradox Basin; (2) asymmetry across the salt wall flanks, resulting in different amounts of accommodation and stratigraphic thicknesses; (3) the important relationship between eolian deposition of the White Rim Sandstone and the timing of the rise of the Castle Valley salt wall; (4) the amount of faulting along salt wall terminations and the resulting compartmentalization; (5) the development of multiple halokinetic sequences in response to passive diapirism of the Gypsum Valley salt wall; (6) growth faulting at Klondike Ridge associated with failure of the stratigraphy to imitate the salt wall termination; (7) the potential to better predict White Rim Sandstone petroleum reservoirs throughout the basin; (8) the possibility of new petroleum plays along the southern flank of the Gypsum Valley salt wall termination. The results of this study indicate that modeling of salt wall terminations is essential to understanding the complexity associated with salt structures. Furthermore, these models provide insight into other systems and may help with improved petroleum exploration and production. In areas such as the Gulf of Mexico, diapiric Jurassic Louann Salt produces irregularly shaped salt structures. The study of the salt wall terminations would be more applicable in these instances than the study of the central, linear parts of the salt walls. Therefore, this study illustrates the significance of three-dimensional models in developing a better understanding of the Paradox Basin and other salt systems.