WAS LATE PALEOZOIC DEFORMATION ALONG THE CORDILLERA A DRIVING FORCE FOR ANCESTRAL ROCKY MOUNTAIN UPLIFTS?

Late Paleozoic compressional deformation at the Cordilleran margin may have contributed to the driving forces for uplift of the Ancestral Rocky Mountains (ARM). Synthesis of research in the northern Adobe Range in Nevada and other published data shows that, in general, late Paleozoic thrust faulting at the Cordilleran margin progressively occurred during the Mississippian in extreme northeastern Nevada, during the Pennsylvanian in north-central Nevada, and during the Permian in southern Nevada and the Death Valley region. This progressive thrust faulting reflects not just a significant deformation event at the late Paleozoic Cordilleran margin, but the most important Cordilleran compressional event(s) during the post-Antler to pre-Sonoma interval. The apparent southwestward migration of compressional deformation at the Cordilleran margin is similar both in age and direction to the apparent southwestward migration over time of the ARM uplifts in the continental interior, which is constrained by ages of sediments in associated basins. Additionally, the apparent migration of compressional deformation at the Cordilleran margin and in the interior is similar both in age and direction to the southwestward migrating Ouachita suture between Gondwana and Laurentia. Where constrained, such as in the Uncompahgre uplift, published data show that structures genetically linked to the ARM uplifts were overall either southwest or northeast vergent. Vergence of ARM uplifts was parallel and contemporaneous to the southwestward progressing Cordilleran margin and the Ouachita suture. Compression between two active deformation zones at both the southeast and northwest margins of Laurentia created a relatively high stress region in the adjacent continental interior. Individual ARM uplifts in the continental interior migrated southwestward over time as deformation at the continental margins progressed to the southwest.