Affiliation: College of Arts and Sciences, Department of Geological Sciences
The Appalachians have a complex history involving a wide range of geologic processes. In recent decades the story of how this ancient orogen has been built up and broken down through multiple cycles of collision and rifting has become richer with investigations into the apparent enigma of mountain building in the absence of obvious tectonic forces. There are features that cannot be explained if the Appalachians are simply the remnants of a once Andean-scale range that has eroded steadily since it was in proximity to a plate margin, such as fracture zones that cut through the mountains that have been studied but not well understood, or active seismic zones that do not seem to belong in a passive margin setting. Many landscapes in the mountains resemble those found near plate margins and have led previous workers to conclude that parts of the Appalachians are the result of a Cenozoic topographic rejuvenation. In this dissertation, I use a multi-faceted approach to propose an explanation of how and why the southern and central Appalachians have uplifted in recent geologic time. In chapter 1, I use an automated analysis of longitudinal stream profiles and flow directions to show how fractures and faults associated with topographic lineaments crossing the mountains can influence erosional processes and landscape development in the Blue Ridge of western North Carolina. In chapter 2, I present the first documented evidence of a seismically active, Cenozoic brittle fault zone associated with blocky uplift of the Appalachians. In chapter 3, I link young landscapes to mantle delamination and attempt to explain why there is a mismatch of topography along the geologic provinces.