FEATURES OF FAULT STRUCTURE IN SOUTHERN MARGIN OF WEST SEGMENT OF THE SOUTH TIANSHAN,AND ITS CONTROL TO EVOLUTION OF THE WUSHI SAG
Zheng Min1, Lei Ganglin2, Huang Shaoying2, Wu Chao2, Luo Shenchao2, Li Yuejun3
1. Lanzhou Oil-Gas Resource Centre, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000; 2. Tarim Oilfield Branch Company, China National Petroleum Corp., Korla, Xinjiang 841000; 3. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029
The Wushi Sag situated to the south of the western segment of the Chinese South Tianshan,with the East Sub-Sag being its main body,and generally being regarded as westward extension of the Kuqa Depression(a Cenozoic molasses basin of intracontinental orogeny in South Tianshan area).Controlled by the Cenozoic intracontinental orogeny in area of the Tianshan Mountains,the Wushi Sag created with the same basin-forming dynamics of the Kuqa Depression.In Wushi,the Cenozoic deformation had different features from the Kuqa Depression,because there was the Wensu Rise,to the south of the Wushi Sag,which resisted southward expanding of the compressional stress,and a NW-striking structural transfer belt(the West Qiultag structural belt) separated the Wushi Sag from the Kuqa Depression. The Meso-Cenozoic strata in the Wushi Sag could be divided,by the gypsum-salt bed in the Miocene Jidike Formation,into two structural layers.Generally speaking,the deformation in the upper structural layer was characterized with back-thrust,and a basement-evolved ramp thrust occurred in the lower structural layer.In addition,a thrust in the Pre-Mesozoic basement should be emphasized,since the Wensu Rise acted once a provenance to the Wushi Sag during Meso-Cenozoic.These deformation features in Wushi might be related to westward migration of the Cenozoic compressional stress,and some thrust deformation absorbed by the strike-slipping along the northern and southern boundaries of the Wushi Sag,which indicated an inheritance of Cenozoic structures to the Hercynian-Indosinian collisional tectonics in the Chinese South Tianshan.The paper expressed briefly tectonic evolution of the South Tianshan orogen,introduced main chatacterictics of boundary fractures of the Wushi Sag,reconstructed Meso-Cenozoic evolution of the Wushi Sag and compared with that of the Kuqa Depression.Based on what mentioned,the paper explored the basin-formation dynamics,analysed the coupled evolution between the Wushi Sag and the South Tianshan orogen,and pointed out that the main target for the oil-gas exploration in Wushi should be Triassic Huangshanjie Formation.
Zheng Min,Lei Ganglin,Huang Shaoying et al. FEATURES OF FAULT STRUCTURE IN SOUTHERN MARGIN OF WEST SEGMENT OF THE SOUTH TIANSHAN,AND ITS CONTROL TO EVOLUTION OF THE WUSHI SAG[J]. Chinese Journal of Geology, 2007, (4): 639-655.