Using Deformation Terraces to Confine the Shortening and Uplift of the Longquan Anticline
详细信息
- 责任者：Li Kang (Key Laboratory of Active Tectonics and Volcano ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Xu Xiwei
- 刊名：Seismology and Geology
- 出版年：2013
- 卷期：35(1)
- 关键词：地壳缩短 ; crustal shortening ; 隆起 ; uplifts ; 龙门山断裂带 ; Longmenshan Fault Zone
- 页码：p.22-36
- 图表：illus., 2 tables, 28 refs.
- 分类号：0300
- issnNo：ISSN0253-4967
- isbnNo：CN11-2192/P
摘要
Located at east of the Longmen Mountains Thrust,the Longquan anticline is a foreland uplift of Sichuan foreland basin. Three terraces have formed along the Kaijiang River across the Longquan anticline. According to optically stimulated luminescence(OSL)and \{14C\} samples,the age of the terrace T1 and T2 is 4.6ka and(11.7±0.4)ka,respectively. With growing of the anticline,terrace surfaces deformed obviously,which is characterized by folding scarps.The longitudinal profiles of the terraces at the Kaijiang River have been measured by differential GPS.We interpret the subsurface fault and fold geometries using petroleum seismic reflection profiles,our data suggest that the Longquan anticline grows laterally through kink-band migration and depth-to-detachment is about 6 kilometers.The cumulative shortening along the direction of tectonic transport is estimated to be 0.8km. We can confine that the crustal shortening and the uplift rate in late Pleistocene is(1.36±0.41)mm/a and(0.64±0.19)mm/a. India colliding with Eurasia results in the strong resistance from the South China block against the E to SEE extrusion of Bayan Har block,most of the energy has released in the form of uplifting of Longmen Mountains,and part,by the decollement,has been transferred to form the Longquan anticline.The 12 May 2008 Wenchuan earthquake(MW=7.9)of China occurred in the Longmen Shan thrust belt and is a consequence of the ongoing uplift process of the eastern margin of Tibetan plateau. After the earthquake,stress was reduced on the northern section and increased on the southern section of Longquan Fault.The event clearly illustrates that the Longquan anticline and the Longmen Shan thrust belt is an integral whole.The mechanism of uplift of Longquan Mountains provides some evidence for the orogenic model of brittle crustal thickening in the eastern Tibet Plateau.
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