T21A-2808
Structural geometry, kinematics and deformation mechanism of southwestern Sichuan Basin, China: Implications for the eastward-growth of the southeast margin of the Tibetan Plateau
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Yingqiang Li, The Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism, the Ministry of Education, China University of Geosciences, Beijing 100083, China, Beijing, China, Dengfa He, China University of Geosciences Beijing, School of Energy Resoureces, Beijing, China, Renqi Lu, Department of Geoscience, National Taiwan University, Taipei, Taiwan and Jinwei Gao, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Abstract:
The southwestern Sichuan area is located on the southeastern Tibetan Plateau, including the south segment of Longmenshan Mountains and some secondary structural belts. Based on structural geology, low temperature chronology and fault-related fold theory, integrated with the latest surface geology, magnetic, seismic and drilling data, the paper well interpreted seismic reflection profiles, constrained the tectonic deformation time, analyzed the structural geometrics and kinematics, restored the structural evolution, discussed the formation mechanism, and provided some constraints on the eastward-growth of the southeast margin of the Tibetan Plateau. The southwestern Sichuan area was divided into three tectonic belts from northwest to southeast: the Longmenshan tectonic belt, Xiongpo tectonic belt and the Longquanshan tectonic belt. Each belt produced stratified deformation with the basement ductile shear layer and the Middle-Lower Triassic salt layer as the detachment fault.The tectonic deformation in front of the south segment of Longmenshan Mountains varies along the structural trend. Wedge structures developed in mid-depth of the north part of Gaojiachang－Sanhechang belt, while the shallow dominated by the combination of fault and fold. The deep and mid-shallow layer of the south part characterized by duplex structure and superposed wedge structures. The crustal shortening of south part is much larger than the north, and the shallow layer is larger than the deep, with maximum shortening of 14.5 km (38%). The tectonic history (deformation) experienced sea-land changes in the Late Triassic → the rise of the south segment of Longmenshan Mountains and formation of Longquanshan thrust belt in the Middle Jurassic → the formation of Xiongpo thrust belt during the Late Eocene and Miocene → the expansion of the south segment of Longmenshan Mountains since the Pliocene. Linking structural geometry and deformation mechanism of major structural belts in southwestern Sichuan Basin, we argue an eastward-growth pattern of the southeast margin of the Tibetan Plateau.
