HR: 1340h
AN: H53C-1404    [Abstracts]
TI: Debris flows as agents of landscape evolution in quartzite terrains of the central Appalachians, Virginia
AU: * Sas, R J
EM: sasrj@sfsu.edu
AF: Department of Geosciences, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, United States
AU: Eaton, L S
EM: eatonls@jmu.edu
AF: Department of Geology and Environmental Science, James Madison University, 800 South Main Street, Harrisonburg, VA 22807, United States
AB: Debris flows that impacted the central Blue Ridge Mountains of Virginia in 1995 provided unique insight into the landscape development of quartzite terrains. A pervasive pattern of bedrock joints and bedding planes forms orthogonal fracture systems that control denudation by debris slides and debris flows. Fracture recharge may serve to substantially increase rock pore pressure during high intensity rainfall, especially when coupled with antecedent moisture. The high-angle wedge-failure observed at debris-flow initiation sites possesses a similar geometry to that of the regional, mountainous landforms. The ubiquity of this geometry at all scales (i.e., outcrop, hillslope, and mountain) indicates that debris-flows are an important process in long term landscape evolution. Furthermore, the large volumes of sediment removed from relatively small basins indicate that debris flows are significant agents of denudation and sediment transport in the study region. Debris flows are episodic in this region as indicated by radiocarbon dating of a buried soil horizon, quantification of soil profile development, and stratigraphic relationships among debris-flow deposits. We estimate an approximate debris flow recurrence interval of 2000 to 4000 years for major regional events in this terrain during the Holocene.
DE: 1130 Geomorphological geochronology
DE: 1810 Debris flow and landslides
DE: 1826 Geomorphology: hillslope (1625)
DE: 1859 Rocks: physical properties
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: 2007 Fall Meeting