The Structural Characteristics And Tectonic Evolution Of Yiyang Basin

Yiyang basin is a Cretaceous continental sedimentary basin under the control of Jiangshao fault zone, the structural deformation and tectonic evolution characteristics has long been a lack of necessary research. Based on previous data, through a lot of field geological work and combined with the regional dynamics background to discuss the structural features, the basin structure, the evolution history and sedimentary basin forming dynamics and other issues in Yiyang basin.Based on the field work, this paper fixed the basin of the four sets of rock stratigraphic unit and key unconformity, detailed analysis on geometry and kinematic characteristics of the tectonic deformation in the basin, identified the different stratigraphic units and different parts of tectonic deformation law. According to the sedimentary and structural characteristics, the Yiyang basin is divided into 3 second-class structural units and 7 third-class structural units. In this basin, overall it is mainly fault-depression structure but the local has fault-super structure in section. Analysis of the basement structure shows that the characteristics of basin basement are significant, and the difference of basal characteristics of different zones is great, which controls the sedimentary and tectonic framework of the basin.With the stress field analysis shows that the Yiyang basin has experienced 4 times of extension and 5 times of extrusion, respectively is NWW-SEE, NW-SE, NNW-SSE and near SN to extensional and NWW-SEE, NW-SE, NNW-SSE, near SN and NE-SW to extrusion. Sedimentary and structural characteristics show that the Yiyang basin has experienced 5 basin-forming stages as volcanic down-faulting stage, sedimentary down-faulting stage, downwarped-faulting stage, fault basin stage and depression basin stage, meanwhile, it has experienced 5 basin inversion stages.Comprehensive analysis shows that the basin forming dynamic factors of Yiyang basin includes back-arc extension of marginal pacific subduction systems the regional lithosphere extension thinning and boundary effect and weakened basement of Jiangshao fault zone. Due to the difference of regional location and control of Jiangshao fault zone, Yiyang basin are obviously different from the same period of Cretaceous basins in southeast coast on shapes of basin, sedimentary characteristics, basin structure, tectonic deformation, evolution history, sedimentary basin forming dynamic characteristics and so on.