Heterogeneous Laramide Deformation in the Uinta Mountains, Colorado and Utah

Previous explanations for the diverse trends of Laramide structures in the Rocky Mountain foreland include reactivation of pre-existing structures, multiple phases of deformation, and complex responses to regional rotations and wrench faults. Recent studies of slickensided minor faults in the east-trending Uinta Arch of the central Rocky Mountains indicate .heterogeneous, oblique-slip displacement and oblique stress orientations. In the northern Uinta Arch near Flaming Gorge Reservoir, minor faults and stress tensor inversions indicate northeast-trending average slip and bl orientations consistent with average regional trends and other foreland studies. In the southern Uintas at Dinosaur National Monument, however, a complex array of minor faults indicates south- to southeast-trending slip and b1 orientations, sub-perpendicular to local faults and folds. A three-dimensional structural restoration confirms "W-SSE shortening in the Dinosaur area. The variable bl directions demonstrate heierogeneous stress within the Uinta c 2) right lateral shear due-to the complex transition in structural vergence between the northeastdirected Uinta Arch and southwest-directed White River Uplift; and/or 3) eastward translation of the Uinta structural block due to impingement of the Sevier thrusts to the west.