塔里木盆地西部喀什凹陷褶皱冲断带的构造特征

喀什凹陷南部和北部分别发育西昆仑北缘褶皱冲断带和南天山南缘褶皱冲断带,它们具有不同的构造特征。南天山南缘褶皱冲断带南北分带,东西分段,东段变形一般强于西段,同时还受到塔拉斯-费尔干纳断裂的影响。西昆仑北缘褶皱冲断带受到帕米尔弧的影响较大,造山带内部的蛇绿混杂岩已被卷入冲断带,冲断带中的许多地层已经倒转,此外还发育规模较大的乌帕尔-膘尔托阔依背驮盆地。两个褶皱冲断带内部前中生界差异较大,中生界以上的差异逐渐减小,表明喀什凹陷中生代以来才成为一个统一的沉积单元。两个褶皱冲断带中的地层不整合并非严格一一对应,西昆仑北缘褶皱冲断带中的地层不整合多于南天山南缘褶皱冲断带,而且层位偏低,表明西昆仑北缘褶皱冲断带的发育时间稍早于南天山南缘褶皱冲断带,而且冲断活动也强于南天山南缘褶皱冲断带。

Structural features of fold-thrust zone in Kashi depression,western Tarim basin

Fold thrust zones in northern edge of Western Kunlun and in southern edge of Southern Tianshan,with different structural features,are developed in southern and northern Kashi depression,respectively.The fold thrust zone in southern edge of Southern Tianshan is characterized by its S N zonation and E W segmentation;deformation in the eastern segment is generally stronger than that in the western segment,and it is also affected by the Talas Ferghana fracture.The fold thrust zone in northern edge of Western Kunlun is relatively heavily influenced by the Pamir Arc.The ophiolitic melange in the orogenic zone have been involved in the thrust zone where many formations are inverted.Besides,a large Wupoer Piaoertuokuoyi piggyback basin is developed.Difference between the pre Mesozoic in the two fold thrust zones is significant,while it decreases progressively upward,indicating that Kashi depression has evolved into a unique sedimentary unit since Mesozoic.The unconformities do not strictly correspond to each other in the two fold thrust zones.The number of unconformities in the fold thrust zone in northern edge of Western Kunlun is larger,and the horizon is lower than that in the southern edge of Southern Tianshan,revealing that the development of the former is a little bit earlier and the thrusting is stronger than that of the latter.