--> A New Insight on the Mechanism of Salt Wall Collapse in Northeastern Paradox Basin, Utah

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A New Insight on the Mechanism of Salt Wall Collapse in Northeastern Paradox Basin, Utah

Abstract

The northeastern Paradox basin is characterized by a series of salt cored anticlines (salt walls) trending NW-SE. The crestal areas of the salt cored anticlines are breached and cut by faults. In the core of the salt walls, valleys are created by subsidence of the crestal overburden. There has always been a debate about the mechanism of the subsidence of the anticline crest. Some researchers, based on field observations favor the dissolution of the salt, as the main mechanism for the crestal subsidence. Others, based on physical modeling, favor a tectonic factor, with regional extension, as the main mechanism that triggered the subsidence. A 3D seismic dataset covering the northern end of Salt Valley Salt Wall in the northeastern part of the Paradox Basin presents a unique opportunity to investigate and provide a new perspective on the origin of the collapse structures. Interpretation of the seismic data shows a graben system that formed in the crestal area of the salt wall. The graben system has a maximum displacement at the NW end decreasing toward the central part of the salt wall toward the SE. The maximum displacement occurs where the salt crest is deepest and the minimum displacement, where the salt crest is highest. The data suggest the displacement of the graben system might be attributed to lateral salt migration within the salt wall. Salt migrates from where the overburden is thickest (higher pressure head) toward the central part of the salt wall where the overburden is thinnest (lower pressure head). However, extensional faults might help increase the groundwater circulation in the areas where the salt wall is closer to the surface. This might also enhance salt dissolution in those areas, which triggered the salt to flow from deeper levels and along the strike of the salt wall. Several 2D numerical forward models were performed to test the hypothesis of the internal salt migration. This preliminary work suggests that the mechanism for the formation of the salt valleys might be attributed to multiple factors (i.e., extensional forces, salt dissolution and internal salt flow) rather than favoring a single mechanism for the formation of the salt valleys in the northeastern Paradox Basin. The findings of this work might also be applied to other fault systems that exist at the end of the salt structures in the Paradox Basin (e.g., Moab, Fisher valley and Castle valley salt walls).