塔里木盆地西北缘古木别孜断裂变形特征和构造转换

Deformation features and tectonic transfer of the Gumubiezi Fault in the northwestern margin of Tarim Basin,NW China

通过野外地质调查、地震反射剖面的精细解释和钻井资料分析,对塔里木盆地古木别孜断裂从东到西的变形差异、构造转换及导致其在空间上差异变化的控制因素进行系统研究。第四纪早期古木别孜断裂开始沿着中新统吉迪克组含膏泥岩层向南挤压滑脱,并在温宿凸起北缘突破到地表,在断裂上盘形成古木别孜背斜。古木别孜断裂滑移量从东段A—A′剖面的1.21 km向西至C—C′剖面减小为0.39 km,并在古木别孜背斜以西区域完全消失。该断裂的滑移量一部分转换为前锋逆冲量,另一部分被上盘古木别孜背斜所吸收。古木别孜断裂的形成与吉迪克组含膏泥岩层的发育和温宿古隆起的阻挡作用有关,而古木别孜构造带自东向西在空间上变形差异受控于吉迪克组含膏泥岩层的发育程度:东段吉迪克组含膏泥岩厚度大,剖面北侧的深部双重构造变形量较多地沿含膏泥岩层向盆地内部滑脱传递;往西吉迪克组含膏泥岩厚度变小,深部双重构造变形量沿含膏泥岩向盆地内部传递逐渐减小;西段D—D′剖面的含膏泥岩不发育,深部双重构造的变形量无法沿吉迪克组向盆地内滑脱传递,深部逆冲断层向地表突破,古木别孜断裂完全消失。古木别孜断裂滑移量向西最终消失是通过侧断坡来实现构造转换的。

Through field geologic survey,fine interpretation of seismic reflection data and analysis of well drilling data,the differential deformation,tectonic transfer and controlling factors of the differential deformation of the Gumubiezi Fault(GF)from east to west have been studied systematically.The study shows that GF started to move southward as a compressive decollement along the Miocene gypsum-bearing mudstone layer in the Jidike Formation at the Early Quaternary and thrust out of the ground surface at the northern margin of the Wensu Uplift,and the Gumubiezi anticline formed on the hanging wall of the GF.The displacement of the GF decreases gradually from 1.21 km in the east AA′transect to 0.39 km in the west CC′transect,and completely disappears in the west of the Gumubiezi anticline.One part of the displacement of the GF is converted into the forward thrust,and another part is absorbed by the hanging wall of Gumubiezi anticline.The formation of the GF is related to the gypsum-bearing mudstone layer in the Jidike Formation and barrier of the Wensu Uplift.The differential deformation of the GF from east to west is controlled by the development difference of gypsum-bearing mudstone layer in the Jidike Formation.In the east part,gypsum-bearing mudstone layer in the Jidike Formation is thicker,the deformation of the duplex structure in the north of the profile transferred to the basin along gypsum-bearing mudstone layer;to the west of the Gumubiezi structural belt(GSB),the gypsum-bearing mudstone layer in Jidike Formation decreases in thickness,and the transfer quantity of deformation of the duplex structure along the gypsum-bearing mudstone layer to the basin gradually reduces.In contrast,on the west DD′profile,the gypsum-bearing mudstone is not developed,the deformation of the deep duplex structure cannot be transferred along the Jidike Formation into the basin,the deep thrust fault broke to the surface and the GF disappeared completely.The displacement of the GF to the west eventually disappeared,because the lateral ramp acts as the transitional fault between east and west part of GSB.