Three-dimensional Laramide deformation of the Colorado Plateau: Competing stresses from the Sevier thrust belt and the flat Farallon slab

Kinematic analysis of Laramide basement-cored uplifts on the northern Colorado Plateau indicate that four of the uplifts were constructed by northeast directed shortening while at least two were constructed by southeast directed shortening. Available timing data suggest that all of the uplifts rose at approximately the same time (similar to72-50 Ma). This paper proposes that the different shortening directions are a predictable result of deformation in a three-dimensional stress field where the magnitude of sigma(2) approaches that of sigma(1). The concept is supported by both Angelier stereographic analysis and elastic modeling. Tectonically, sigma(1) is may have been the result of coupling between the horizontally subducting Farallon slab and the North American plate. The elevated values of sigma(2) are attributed to far-field stresses generated by the topographically high Sevier thrust belt which wraps around the western edge of the Colorado Plateau and was active at the time of deformation in the Plateau.