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Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau.

Densmore, A.L. and Ellis, M.A. and Li, Y. and Zhou, R. and Hancock, G. S. and Richardson, N. (2007) 'Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau.', Tectonics., 26 . TC4005.

Abstract

The steep, high-relief eastern margin of the Tibetan Plateau has undergone rapid Cenozoic cooling and denudation yet shows little evidence for large-magnitude shortening or accommodation generation in the foreland basin. We address this paradox by using a variety of geomorphic observations to place constraints on the kinematics and slip rates of several large faults that parallel the plateau margin. The Beichuan and Pengguan faults are active, dominantly dextral-slip structures that can be traced continuously for up to 200 km along the plateau margin. Both faults offset fluvial fill terraces that yield inheritance-corrected, cosmogenic 10Be exposure ages of <15 kyr, indicating latest Pleistocene activity. The Pengguan fault appears to have been active in the Holocene at two sites along strike. Latest Quaternary apparent throw rates on both faults are variable along strike but are typically <1 mm yr−1. Rates of strike-slip displacement are likely to be several times higher, probably ∼1–10 mm yr−1 but remain poorly constrained. Late Quaternary folding and dextral strike-slip has also occurred along the western margin of the Sichuan Basin, particularly associated with the present-day mountain front. These observations support models for the formation and maintenance of the eastern plateau margin that do not involve major upper crustal shortening. They also suggest that activity on the margin-parallel faults in eastern Tibet may represent a significant seismic hazard to the densely populated Sichuan Basin.

Item Type:Article
Keywords:Tibetan Plateau, Geomorphology.
Full text:PDF - Published Version (1110Kb)
Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1029/2006TC001987
Publisher statement:© 2007 American Geophysical Union. Densmore, A. L., M. A. Ellis, Y. Li, R. Zhou, G. S. Hancock, and N. Richardson, (2007), Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau, Tectonics, 26, TC4005, 10.1029/2006TC001987. To view the published open abstract, go to http://dx.doi.org and enter the DOI
Record Created:06 Aug 2010 10:05
Last Modified:10 Oct 2013 12:32

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