EROSION RATE OF THE APPALACHIAN PLATEAU IN THE VICINITY OF THE NEW RIVER GORGE, WEST VIRGINIA

The New River splits the flat-topped Appalachian Plateau of West Virginia in a gorge up to 500 meters deep. This landscape is thought to result from the exceptional erosional resistance of the New River Formation sandstone, which locally caps the plateau. To test this hypothesis, we measured cosmogenic 10Be concentrations in sediment from streams that exclusively drain the New River Formation, as well as from soil on undisturbed hilltops. Because the New River Formation is an important source of coal, great care was taken to avoid watersheds impacted by mining or other development.

Our results indicate that basin-averaged erosion rates range from 7-10 m/My, and that local hilltop erosion rates range from 4-11 m/My. These erosion rates are substantially slower than those measured elsewhere in the Appalachian Mountains, which tend to range from 20-40 m/My. Incision rates of the New River have been measured at multiple sites both upstream and downstream of our study area, yielding rates of approximately 30 m/My over the past 1-2 million years. These results suggest that the New River’s incision rate is in equilibrium with erosion rates in the Appalachian Mountains upstream of the gorge, and that the gorge has developed due to the erosional resistance of the New River formation. Although we cannot justifiably extrapolate our results to the past, if the incision rates and erosion rates of this study have remained constant, then the New River gorge could have formed over the past 20 million years.

During the course of this project, we developed an improved method for separating quartz using heated rollers instead of the customary ultrasonic tank. We will present a brief comparison of these two methods.