EXPLORING THE ORIGINS OF MODERN TOPOGRAPHIC RELIEF IN THE SOUTH APPALACHIANS

The southern Appalachian Mountains share many characteristics associated with tectonically active settings, including locally high topographic relief, steep slopes, incised river gorges and frequent mass-wasting events, yet tectonic active in the region presumably ceased shortly after the initiation of rifting of the North Atlantic Margin in the Triassic. Two competing hypotheses are commonly invoked to explain their modern rugged topographic expression. One suggests that topography has persisted though time in a dynamic equilibrium, with relief largely controlled by varying lithologic resistance to weathering. The second forwards that modern relief is a recent product of a period of rejuvenation; however, whether the process governing this resurgence is climate change or dynamic mantle flow is debated. We present results from a drainage basin in the southern Appalachians demonstrating that relief has increased > 100 % in the late Cenozoic and pre-dates the shift to rapidly changing climate conditions. This evidence suggests that climate change is not the fundamental process responsible for the modern Appalachian topography, and instead favors a model where relief develops as the landscape is dynamically uplifted. This research illustrates that the earth’s surface records relevant spatial and temporal information about processes possibly acting in the earth’s lower-crust and upper-mantle. This investigation brings forward multiple hypotheses about the late Cenozoic evolution of the southern Appalachians, some that are testable with the arrival of the EarthScope USArray seismic observatory experiment in the eastern United States. Our findings encourage future collaboration between the geomorphic and geophysical communities to answer questions related to the post-orogenic evolution of the southern Appalachians.