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Active Tectonics in Southern Xinjiang, China: Analysis of Terrace Riser and Normal Fault Scarp Degradation Along the Hotan-Qira Fault System

Avouac, Jean-Philippe and Peltzer, Gilles (1993) Active Tectonics in Southern Xinjiang, China: Analysis of Terrace Riser and Normal Fault Scarp Degradation Along the Hotan-Qira Fault System. Journal of Geophysical Research B, 98 (B12). pp. 21773-21807. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:20120911-103543102

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Abstract

The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan-Qira oases, by a set of normal faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan-Qira normal fault system vertically offsets the piedmont slope by 70 m. Highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwalls have formed inset terraces. We have leveled topographic profiles across fault scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient τ, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 ± 4 m^2. Profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model. The analysis shows that (1) rate of fault slip remained essentially constant since the aggradation of the piedmont surface and (2) the occurrence of inset terraces was synchronous at all studied sites, suggesting a climate-driven terrace formation. Observation of glacial and periglacial geomorphic features along the northern front of the western Kunlun range indicates that the Qira glaciofluvial fan emplaced after the last glacial maximum, during the retreat of the Kunlun glaciers (12–22 ka). The age of the most developed inset terrace in uplifted valleys is inferred to be 10 ± 3 ka, coeval with humid climate pulses of the last deglaciation. The mass diffusivity constant (k=τ/T, being time B.P.) in the Hotan region is determined to be 3.3 ± 1.4 m^2/10^3 years, consistent with other estimates in similar climatic and geologic environments of western China. These results imply a minimum rate for the Tarim subsidence of 3.5 ± 2 mm/yr. If Western Kunlun overthrusts the Tarim platform on a crustal ramp dipping 40°–45° to the south, it would absorb at least 4.5 ± 3 mm/yr of convergence between western Tibet and Tarim.


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Additional Information:© 1993 American Geophysical Union. Received October 10, 1990; revised July 26, 1993; accepted July 30, 1993. The research described in this paper was carried out by the Institute de Physique du Globe de Paris (France) and the Jet Propulsion Laboratory, California Institute of Technology, respectively, under contract with the Centre National de la Recherche Scientifique and the National Aeronautics and Space Administration. We are grateful to Paul Tapponnier who discovered the Hotan fault on Landsat images and pinpointed the interest of the site. Numerous discussions with him were essential and enlightening. Special thanks goes to Pierre Gentelle for supporting one of us (J>P>A.) during the field campaign, and Liang Kuang Yi for the organization of the field program. We also benefitted from discussion with Tom Farr, Diane Evans, and Pierre Gentelle. Guy Aveline drafted the figures and maps. Comments by Thomas Hanks were very helpful. We thank Thomas Hanks and lark Burchfiel for reviewing the paper. This IPGP contribution 1267.
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Record Number:CaltechAUTHORS:20120911-103543102
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120911-103543102
Official Citation: Avouac, J.-P., and G. Peltzer (1993), Active Tectonics in Southern Xinjiang, China: Analysis of Terrace Riser and Normal Fault Scarp Degradation Along the Hotan-Qira Fault System, J. Geophys. Res., 98(B12), 21,773–21,807, doi:10.1029/93JB02172.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33990
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:11 Sep 2012 18:04
Last Modified:26 Dec 2012 16:08

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