Multiscale Integration of Empirical Geologic Observations with Quantitative Structural Modeling to Constrain Late Cretaceous to Eocene Paleostress Environments on the Colorado Plateau

Abstract

Relating crustal deformation to stress conditions has long been a subject of interest to the geologic community as rock failure has important implications for storage and extraction of petroleum and mineral deposits, as well as sequestration efforts. The ability to relate patterns of rock deformation to stress conditions also permits geologists to better understand structural evolution. This dissertation focuses on interpreting and modeling crustal stress conditions from outcrop to regional scale associated with late Cretaceous to early Eocene deformation across the Colorado Plateau.The first part of this dissertation focuses on salt-related stress perturbations adjacent to the Salt Valley salt wall in the Paradox Basin of southern Utah. Under Late Cretaceous-early Eocene tectonic loading, the salt wall underwent active diapirism via ductile flow because of its inability to sustain differential stress due to inherent mechanical weakness. This phenomenon generated local stress perturbations from regional tectonic conditions in the rock mass adjacent to the deforming salt wall. The first two studies presented in this dissertation improve our ability to interpret and predict stress conditions and the associated rock failure in the perturbed stress environment around salt bodies under tectonic loading. This includes evidence and implications for use of a non-linear failure criterion to describe brittle rock failure, as opposed to the commonly used linear Coulomb failure criterion. The second part of this dissertation focuses on regional tectonic stress and associated Laramide deformation across the Colorado Plateau. Laramide deformation is evidenced by basement-cored uplifts bound by doubly plunging monoclinal folds. Blind basement fault geometries are estimated with trishear fault-propagation models and generalized area-depth calculations. The blind basement fault model is used as inputs into a geomechanical model to evaluate regional Laramide stress conditions responsible for observed deformation patterns across the Colorado Plateau. Throughout each section of this dissertation, I employ well known structural geologic techniques, such as fracture analysis and geomechanical modeling, in new and integrative ways to provide a unique perspective and approach to problems in structural geology research.