GEOMORPHOLOGICAL RESPONSES TO CENOZOIC SLIP ON THE BOONE FAULT

The WNW-trending Boone lineament swarm spans ~180 km from the Piedmont of North Carolina, through the Blue Ridge, and into the Valley and Ridge of Tennessee. Within this orogen-crossing series of trenches, and along the NW edge of the Grandfather Mountain window, lies the Boone fault, where we mapped a 10 km-long vertical fault zone that is likely Cenozoic in age. Structures associated with the Boone fault include abundant fractures and minor faults and these features have had a significant influence on the geomorphology of this part of the Appalachians. The Deep Gap reentrant along the Blue Ridge escarpment is a major geomorphological feature that is the locus of abundant historical and modern landslides, and likely is a result of the bedrock being strongly fractured within the lineament swarm. To support our claim that the Boone fault has had Cenozoic motion, we extracted longitudinal profiles of streams draining across the fault and into the South New River. The streams contain dozens of knickpoints 200-400m above the fault, as well as hook-shaped headwaters consistent with stream capture driven by divide migration that was the result of south-side-up motion on the fault. We extracted the profiles of the nearby Watauga River and found evidence that this river system was redirected towards the northwest by uplift along the Boone fault, and likely fed into the South New River prior to faulting. The combination of brittle deformation, enhanced erosion along fracture-controlled lineaments, and stream capture and disequilibrium provide evidence of Cenozoic deformation in this area. We think that upper mantle reorganization drove Cenozoic uplift and is the mechanism that formed the Boone lineament swarm, as well as other E-W and WNW-ESE lineaments found throughout the southern Appalachians.