The Tectonic Evolution And Geological Significance Of Xuancheng-Guangde Basin

At present,a large number of meso-cenozoic continental basins in China have been found to contain oil and gas.However,the xuan-guang basin,which is distributed in the inner part of the lower Yangtze plate,has not made a breakthrough in oil and gas field,and its research is relatively low.Based on the analysis and arrangement of the predecessors' research data with the tectonic geology research as the main line,the paper has done a full research on the problems on the structure characteristics,basin structure,the evolution history and dynamic mechanism of forming the basin and so on of XuanGuang basin through a large number of field geological investigation and laboratory analysis combined with the regional dynamics background.lt is believed that the basement of the basin is composed of the marine deposition duriing sinian to Middle Triassic its basement has experienced a series of tectonic deformation including that the foreland deformation engendered by orogenic thrust compression in Indosinian epoch and left-slipping shear occurred in during late Jurassic to early Cretaceous.XuanGuang basin belongs to superimpose rift-subsidence basin formed by extensional faults during early Cretaceous to Paleogene,it has the characteristics of west-faulting east-overlapping and low gravity and magnetism in the area of the basin;Reversals have occurred since the Neogene due to thrust compressions.In this paper,the dynamic background of basin formation is discussed.The basin base is located in the passive continental margin environment from Sinian to Middle Triassic,mainly accepting Marine deposits.The foreland fold and the deformation of thrust compression was developed due to continent-continent collision between South China plate and North China plate caused by Indosinian movement.Since the Mesozoic(J3?K1),the basement has experienced left-row translational shear due to the oblique subduction of the Pacific plate;Regional extensional normal faults(controlling basin formation)were formed due to Pacific plate and upwelling of the regional mantle during late K1 to Paleogene.Since Neogene,the basin has been still uplifted and reversed by oblique subduction of the Pacific plate.