EMPIRICALLY CONSTRAINED ELASTIC DISLOCATION MODELING OF PERTURBED STRESS REGIMES IN THE ROCK MASS ABOVE AN ACTIVE SALT DIAPIR DURING FORCED FOLDING

Rock formations composed of evaporate deposits are orders of magnitude weaker than other rock types. Thus, in natural geologic environments, the salt-sediment interface marks a stark mechanical contrast with distinctive deformation mechanisms between the salt body and the surrounding rock mass. Salt will internally deform via ductile mechanisms, even under very low magnitudes of applied differential stress. As a salt body internally flows in response to an applied driving stress, it perturbs the local stress field felt by the adjacent rock mass. This study explores the salt-related stress perturbation phenomenon with a case study along a deformed margin of the exhumed Salt Valley salt wall in the Paradox Basin of southern Utah. This field-based study documents paleostress-indicative fracture patterns in the rock mass immediately adjacent to the salt-sediment interface. This dataset implies a significant modification in both local stress regime (normal, strike-slip) and differential stress magnitudes relative to the regional compressive stress during forced folding and active diapirism. Direct field measurements are augmented with unmanned aerial vehicle (UAV)-derived point cloud analysis for broad spatial coverage of fracture distribution and orientations to constrain a geomechanical stress model. Although the finite element method is ordinarily utilized to simulate high-strain salt deformation, our work applies the alternative, computationally efficient, elastic dislocation method to simulate deformation in the adjacent rock mass. We present both the salt-related stress change indicated by a comprehensive field-based strain dataset and the applicability of an elastic dislocation stress model to solve for stress field perturbations and synchronous fracture development and fluid flow in a rock mass adjacent to salt bodies.