HR: 0830h
AN: T21C-0471    [PDF]
TI: Uplift and River Incision Within the Eastern Margin of the Tibetan Plateau from Regional Patterns of Channel Steepness
AU: * Ouimet, W
EM: wouimet@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
AU: Whipple, K
EM: kxw@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
AU: Kirby, E
EM: ekirby@geosc.psu.edu
AF: Department of Geosciences, Penn State University, University Park, PA 16802
AU: Clark, M
EM: mclark@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, Pasad, CA 91125
AB: Channel profiles extracted from a digital elevation model of the eastern margin of the Tibetan Plateau reveal a zone of steep river channels around the western edge of the Sichuan Basin that continues west into the plateau, linking dynamic geomorphic processes to tectonic deformation within the region. The eastern margin of the Tibetan Plateau is a highly dissected landscape, characterized by steep river gorges cut 2 to 3 km deep into a broadly uplifting margin where mean elevations typically range from 3500 to 4000 m. We created a normalized steepness index for the eastern margin of the Tibetan plateau; the channels we studied are all within major tributaries of the Yangtze River. Moderately high channel steepness values are focused along the topographic front surrounding the Sichuan basin within deep river gorges that dissect the plateau margin. Channels away from the topographic front, which lie higher up on the plateau surface within a low-relief landscape, are characterized by much lower channel steepness values. The highest steepness values within the region are found in two places: within the lower half of the Dadu River basin, on the eastern slopes of the Gonga Mountains, which rise to more than 7500 m, and within the Yalong River Gorge, on tributaries as they enter the main river. Steep channels highlight important aspects of the tectonic and geomorphic evolution of the plateau margin: uplift and river incision. Broad, long-wavelength uplift of the eastern margin of the Tibetan plateau is associated with the India-Asia collision. Recent tectonic and geomorphic investigations suggest that Late Cenozoic, short-wavelength deformation and uplift has been focused in areas adjacent to the Sichuan Basin. Uplift of the eastern margin has induced dramatic changes in the major river systems that drain this landscape, including the re-organization of drainages and consequent river capture, in combination with major down-cutting and increased channel steepness values as rivers adjust to higher uplift rates.
DE: 1824 Geomorphology (1625)
DE: 8107 Continental neotectonics
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2003 Fall Meeting