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

摘要

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 (～72-50 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 σ_2 approaches that of σ_1. The concept is supported by both Angelier stereographic analysis and elastic modeling. Tectonically, σ_1 is may have been the result of coupling between the horizontally subducting Farallon slab and the North American plate. The elevated values of σ_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.