Late Cenozoic uplift of southeastern Tibet

Recent field work and DEM analysis show that remnant, local areas of a low-relief land scape (or "erosion surface") are geographically continuous across the southeastern Tibetan Plateau margin and can be correlated in order to define the maximum envelope of topogra phy of the margin itself. This observation contradicts earlier notions that the low-gradient plateau margin slope (i.e. the maximum elevation of the margin) is a product of landscape dissection and reduction by fluvial incision due to the presence of major rivers which drain this portion of the plateau and plateau margins. Although initial development of the erosion surface is likely diachronous, we propose that a continuous low-relief landscape existed at low elevations prior to uplift and long-wavelength tilt of the southeastern plateau margin. The modern altitude of the erosion surface provides an excellent datum for constraining the total amount of surface uplift of the southeastern plateau margin. The long-wavelength tilt of the surface across the plateau margin without major disruption mirrors the low-gradient decrease in crustal thickness across the plateau margin, which suggests that crustal thickening has occurred in a distributed manner. Because large-magnitude compressional structures of late Cenozoic age are lacking, we propose that crustal thickening beneath the southeastern plateau margin has largely been accomplished by preferential thickening the lower crust. Perched, relict landscape remnants that reflect slow erosion, low initial elevations and slow uplift rates contrast sharply with the rapidly eroding modern river gorges that incise the surface, indicating that the modern landscape is not in equilibrium. Surface remnants are preserved because incision of the fluvial system has been largely limited to major rivers and principle tributaries, and has not yet progressed throughout the entire fluvial network.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Clark, Marin Kristen, 1973-

Advisor dc:contributor.advisor

• Leigh H. Royden.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29758

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29758