西昆仑山前印支运动期构造对后期构造和沉积的影响

Influences of Indosinian Structures on Later Structural Deformation and Sedimentation in Piedmont of Western Kunlun Mountains

印支运动期古构造对塔里木盆地西南缘西昆仑山前后期的构造变形和侏罗纪—白垩纪的沉积都具有十分重要的控制作用。但由于新生代以来的强烈改造,研究区印支运动期构造特征识别较为困难。选择新生代构造活动相对较弱的西昆仑山前中段,野外露头调查、钻井和地震资料等综合研究表明,西昆仑山前发育印支运动期褶皱冲断带,形成一系列逆冲断层和北东翼陡、南西翼缓的背斜,这与晚三叠世塔里木板块与羌塘地体最终完成陆—陆碰撞形成的北—北东向挤压有关。印支运动期发育的古断层在喜马拉雅运动晚期挤压下复活,从而造成两期背斜上下叠置,构造高点重合。因此,印支运动期构造格局极大地限制了喜马拉雅运动晚期的构造变形。印支运动期古构造奠定了中生代的古地形格局,并对侏罗纪—白垩纪沉积起到了重要的控制作用。受深部印支运动期逆冲断层控制的北西—南东向斜列式分布的古隆起,是造成该区白垩系分布和储集层物性差异的重要原因。

The Indosinian structures exert important controls on the structural deformation in the late stages and sedimentation during Ju?rassic to Cretaceous in the piedmont of the western Kunlun Mountains in the southwestern margin of Tarim basin.It is very difficult to iden?tify the structural features during Indosinian period in the study area due to the strong reworking since Cenozoic.The middle segment of the western Kunlun Mountains where the tectonic activity was relatively weak is selected to be the study object.Based on the comprehensive study on field outcrop,drilling and seismic data,fold thrust belts were developed in the piedmont of the western Kunlun Mountains and a series of thrust faults and the anticlines with steep north and east flanks and gentle south and west flanks were formed,which may be relat?ed to the N?NE compression resulted from the continental collision between the Late Triassic Tarim plate and Qiangtang terrane.These In?dosinian structures were reactivated due to the compression during the Late Himalayan movement,resulting in the superimpositions of the anticlines of two periods and the coincidence of structural highs.Therefore,the structural framework during the Indosinian movement signif?icantly constrained the structural deformation during the Late Himalayan movement.The paleostructure during the Indosinian period laid a foundation for the paleotopographic framework of Mesozoic and played an important control action on the sedimentation during Jurassic to Cretaceous.The NW?SE trending paleohigh controlled by deep?burial thrust faults during Indosinian is the main factor resulting in the dif?ferences in distribution and physical properties of Cretaceous reservoir.