Long, linear, high-relief escarpments mark many of the world's passive margins. These Great Escarpments have been interpreted to be the result of isostatic flexure, parallel slope retreat, and divide migration which accompanies rifting. It is unclear whether all these escarpments share this origin. Also uncertain is whether these features are formed via stable, steady-state processes or by climatic shifts or tectonic rejuvenation. The Blue Ridge Escarpment, eastern North America's great escarpment, is no different. A number of hypotheses attempt to explain the Blue Ridge Escarpment. These include lithologic variation between Blue Ridge and Piedmont rocks, the distance to ultimate base level, as well as, escarpment retreat resulting from post/syn-rift warping or faulting. We approach this problem from two directions. The first involves topographic comparisons and geologic observations to recognize and track divide migration. The second approach uses U-Th/He thermochronometry along two scarp-normal transects. Topographic analysis used data extracted from DEMs to compare three zones - the Upland, the Piedmont and the scarp zone itself. Parameters such as relief, drainage density, hypsometry, and slope are often used as proxies for relative erosion rates and the degree of maturity of a landscape. Results from these analyses indicate that the Upland and Piedmont zones are distinct landscapes, sharing very few topographic similarities, yet neither appears significantly more erodible than the other. Examination of parameters in the proximity of the escarpment point toward more rapid erosion here. Field evidence of this rapid scarp erosion (and thus divide migration) lies in the presence of beheaded stream channels, cobble roundness, and clast provenance. U-Th/He thermochronometry is a low temperature technique that allows us to calculate when rock cooled below 60-70C. Temperature is used as a proxy for depth, from which we can extract an exhumation rate. This method allows us to further test scarp genesis hypotheses. Preliminary results show older ages (~160) from the Upland surface than on the Piedmont lowland (~100 Ma). This confirms that the Piedmont surface is distinct from the Upland and demonstrates that it has experienced greater erosion. There is also some indication that ages "jump" across the Bowens Creek/Brevard fault system. Lastly, the ages appear to become younger approaching the escarpment which is indicative of scarp migration. As these results are preliminary, more data is required to prove or disprove these conclusions. / Master of Science

The Pigeon River watershed has been the focus of a ¬¬major recovery project to reintroduce fish and other aquatic species into the river where they were historically present. A paper mill at Pigeon River Kilometer/Mile (PRKM 102.1/PRM 63.2) began operations in 1908 and discharged effluents which had a detrimental impact on the aquatic wildlife. Recent modifications to the mill have significantly improved effluent quality such that most aquatic organisms are recolonizing the river. The present study is a baseline survey of crayfish species in the Pigeon River and its tributaries; it also includes a comparison of the mean Catch Per Unit Effort (CPUE) in four different reaches of the stream and documents diversity upstream and downstream of the paper mill. Crayfish are important to the aquatic ecosystem and food web because they serve as cutters that help to break down leaf litter and carrion and are also a food source for predators. Crayfish were collected using modified minnow traps and electroshocking and by snorkeling along ‘turning’ rocks; the method used was based on characteristics of the stream reach sampled, including water depth, flow, transparency, and type of substrate. A total of 1,320 crayfish specimens representing seven species was collected during the eight month study. Crayfish were found in nine Pigeon River tributaries , in the main stem of the Pigeon River upstream of the paper mill (PRKM 102.1/PRM 63.2), and below the Progress Energy Dam (PRKM 61.1/PRM 38.0). No crayfish were found downstream of the paper mill in the river itself; however, crayfish were found downstream from the Progress Energy Dam down to the Pigeon River’s confluence with the French Broad River.

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