Sedimentary Responses to Late Cenozoic Thrusting and Strike-slipping of Longmen Shan along Eastern Margin of Tibetan Plateau
LI Yong~ 1 ZHOURong-jun~ 2 Densmore A L~ 3 Ellis M A~ 4 LI Bing~ 1 (1.National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059; 2.Institute of Earthquake Engineering,Seismological Bureau of Sichuan Province,Chengdu 610041; 3.Institute of Geology, Department of Earth Sciences, ETH Zentrum,CH-8092 Zürich, Switzerland; 4.Center for Earthquake Research and Information, University of Memphis,3890 Central Avenue, Memphis, TN 38152,USA)
Chengdu basin developed ahead of Longmen Shan along the eastern margin of Tibetan Plateau, lying between the Longmen Shan and Longquan Shan, and extends from southwest to northeast with the long axis of the basin parallel to Longmen Shan. The filling in the basin with a maximum thickness of 541m include Dayi conglomerate, Yaan gravel layer and Late Pleistocene and Holocene gravel layer. In the transverse section of the basin(vertical to Longmen Shan), the wedge shaped sediments in the basin were derived from Longmen Shan and gradually northwestwards thickening, the depocenter is located in the northwestern part of the basin. As thrusting progressed southeastwards, the northwestern margin and the depocenter of the basin had been progressively migrated southeastwards. According to this evidence, it can be inferred that the direction of trusting and tectonic shorting was from NW-SE and vertical to Longmen Shan. In the longitudinal section (parallel to Longmen Shan), there are many minor echelon depressions and uplifts, as dextral strike-slipping progressed northeastwards, the minor depression (rhombocham) and fan had been progressively migrated northeastwards. According to these lines of evidence, we can infer that the direction of dextral strike-slipping was from SW-NE and parallel to Longmen Shan. So we draw a conclusion that the Chengdu basin is one of typical transpressional basin controlled by thrusting and strike-slipping along Longmen Shan since 3.6Ma.