Strike-slip faulting has played a major role in the tectonic evolution of the northern Cordillera, however the timing, location and mechanisms of much of the strike-slip motion is not well established. Prior work has identified major dextral slip of Cretaceous age along the Border Ranges Fault, Alaska. Preliminary evidence indicates that the present level of erosion exposes the fault near the brittle-ductile transition at the time of motion. Recent models have proposed major subhorizontal detachments in strike-slip systems at this transition, in addition to the steep, strike-slip detachment normally envisioned. Because of the deep level of exposed crust and exceptional outcrop exposure this area affords the opportunity to test these models of the role of subhorizontal detachments in strike-slip shear zones. Results are expected to be applicable to many large-scale strike-slip zones.
