Mesozoic Yanqi Basin Original Features Explore Its Evolution And Post-transformation

Yanqi Basin is a typical reformed residual basin where several oil and gas fields with commercial value and some product energy have been found in recent years. There existed several strong reformation of Late-Yanshan Movement and Himalaya Movement The generation, development, disappearance and reformation are tightly related to Tarim Block, Tianshan Belt and Tethyan tectonic zone, especially Tianshan Belt, which makes the great difference between present and original basin.The base of studying original appearance and its dynamic evolution is sedimentary body of residual basin. By studying the lithologjcal and mineral parameters (Pebbled elastics percent ratio, Clastic maturation index, Heavy crop stability factor) of Mesozoic sedimentary strata, the result shows that the northern boundary of present basin is near to the boundary of original basin and the moving distance of elastics is short, But the southern boundary of present basin is far from the boundary of original basin and the moving distance of elastics is long. The fades of northern basin are mainly delta fades and the fades of middle and southern basin are lacustrine fades. The research on the lithologjcal and mineral parameters and the sedimentary fades of different periods of Mesozoic strata shows that the northern boundary of Yanqi Basin is almost the same, but great differences existed in the southwestern Yanqi Basin, that is, the sedimentary range of Mesozoic original basin is more bigger than present basin.By the comparison of the residual strata, sedimentary evolution and source rocks among Kuche Depression, Kumishi Basin, U'erdusi basin and Yanqi Basin, die result shows that Mesozoic sedimentary environment of these basins has tightly relationship which all belongs to Tarim Basin. From Late-Mesozoic to Eogene, northern edge of Mesozoic Tarim Basin became uplift gradually and the sedimentary range migrate to south. Present U'erdusi Basin, Yanqi Basin, Kumishi Basin became uplift one by one and experienced strong deformation, denudation and reformation and some strata are denuded.By the integrated research on sedimentary-tectonic evolution and reformation of Yanqi Basin and the comparison of die evolution of northern Tarim Basin and Tianshan Belt, the result shows that Yanqi Basin experiences five evolution stages include Forland Basin(T2-3),Extensional Basin(J), Compression and denudation stage(K), Regional depression stage(E), and Broken intracontinental Forland Basin(N+Q). At Mesozoic, Kuche Basin and Yanqi Basin belonged to a unity. At Miocene, southern Tianshan include Kuluketage Mountain uplifted quickly and experienced the stages of independent developing intracontinental Forland Basin and Broken intracontinental Foriand Basin individually.