Analyzing Symmetry of Stream Valleys to Characterize Possible Neogene Uplift in the Blue Ridge Mountains of North Carolina

Recent work has suggested that parts of the Appalachian Mountains were uplifted during the Neogene, based on stream knickpoint analysis (Gallen et al., 2013; Miller et al., 2013). Analysis of the symmetry of valleys has the potential to indicate tectonic activity by determining migration trends of channels. Tectonic quiescence promotes lateral migration of stream bends. This creates asymmetrical bend valleys with shallow point bars and steep cut banks. Uplift promotes downcutting over lateral migration, producing symmetrical stream valleys. Using LIDAR data and ArcMap software, I quantified the symmetry of stream valleys in the Blue Ridge Mountains of western North Carolina. I calculated the symmetry of valleys by dividing the right valley slope by the left valley slope to form ratios ranging from 0 to 1, with 1 indicative of a symmetrical valley. Where the right slope exceeded the left slope, I inverted the ratio to avoid numbers greater than 1. I measured slope ratios across the Broad, Cullasaja, French Broad, Linville, New, Pigeon, Toe, and Tuckasegee Rivers. To separate similar symmetry values between areas of gentle and steep topography, I multiplied the symmetry value by the average of the right and left slopes. The resultant values were then combined with a knickpoint propagation model to project areas of equilibrating streams and relict topography. Active landscapes were projected across most of the Blue Ridge Mountains in North Carolina, excluding the French Broad river valley, which was either unaffected by Neogene activity or equilibrated in the distant past. These conclusions agree with hypothesized locations of active landscapes, in addition to projecting new potential locations of rejuvenation.Bachelor of Scienc