LATE QUATERNARY CRUSTAL SHORTENING RATE OF THE BEILUNTAI FAULT IN SOUTHERN TIAN SHAN,XINJIANG |
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| Authors: | YAO Yuan SONG He-ping CHEN Jian-bo LI Shuai JIA Hai-liang |
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| Institution: | 1. Earthquake Agency of Xinjiang Uygur Autonomous Region, Urumqi 830011, China;
2. School of Architecture and Civil Engineering, Xi'an University of Science and Technology, Xi'an 710000, China |
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| Abstract: | The Beiluntai Fault is a Holocene active fault. It is the boundary between southern Tian Shan and Tarim Basin. Since the late Quaternary, steady activities of the Beiluntai fault have resulted in offsets, folds, and uplift of pluvial terraces. We used the high-resolution RTK topographic surveys to reveal that the fault scarp morphology on the Akeaiken(Ak) segment and Zhuanchang(Zc) segment of the Beiluntai fault. We found that the crustal shortening of Ak and Zc segments are dominated by thrusting and folding-uplift, respectively. We employed th optically stimulated luminescence(OSL) dating method to develop a new chronology for the different pluvial terraces, indicating that they formed at 49.14~58.51, 27±3, 13.72~14.64, 7.13±0.88, (3.32±0.43) ka, respectively. These data permitted to estimate the crustal shortening rate(about 2.4mm/a) remains largely constant on the Ak segment, while the crustal shortening rate of Zc segment was 1.43~1.81mm/a since the Fan4 pluvial terraces was abandoned. Compared with the Ak segment, the crustal shortening rate of the Zc segment declined obviously. This shows that the NS-trending crustal shortening rate of the Beituntai fault decreased gradually from west to east. A comprehensive comparison of the reverse fault-fold belt system in the front of southern Tian Shan also indicates that the crustal shortening rate drops from west to east. |
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| Keywords: | Tian Shan Beiluntai fault thrust fold late Quaternary |
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