YOUNG TOPOGRAPHY, NEW FAULTS, AND MANTLE REORGANIZATION IN AN ANCIENT MOUNTAIN RANGE: A CASE STUDY FROM THE APPALACHIANS

The high topography of the southern and central Appalachians does not coincide with the geologic provinces but instead cuts across them. Located in the Appalachian Plateau of Pennsylvania, the Valley and Ridge of Virginia and West Virginia, and then in the Blue Ridge of North Carolina, this band of rugged topography correlates to areas of high slope and local relief, as well as surfaces we identified with a type of map designed to highlight high peaks and plateaus. We present multiple geomorphic maps to show that the surface of the Appalachians does not always match the underlying bedrock geology, and believe that although currently located in a passive margin, this ancient orogen has undergone a topographic rejuvenation, likely associated with a delaminating mantle. To support our claim that Appalachian topography is partly controlled by drip structures in the mantle, we compare our surface maps to tomographic maps ranging from 36 to 455 km depth. There is a reasonably good fit between the swath of high topography and a seismic anomaly that was recently interpreted as a descending piece of lithospheric mantle (Biryol et al., 2016). It is our interpretation that upper mantle reorganization has driven a Cenozoic rejuvenation of topography and caused many of the structures and landforms that would not exist if the ancient orogenic belt has slowly eroded since the Paleozoic. If mantle deformation is the main driver of the current landscape, it may also be responsible for the formation of the anomalous topographic lineaments that cross the mountain belt and contain young faults, clusters of earthquake epicenters, and abundant landslides within the North Carolina Blue Ridge province.