库车前陆冲断带盐构造区平衡剖面研究

Balanced Cross-sections of Salt Structures in Kuqa Foreland Thrust Belt in Northern Part of Tarim Basin

通过计算库车前陆冲断带古近系库姆格列木组含盐层系初始沉积厚度．并以此作为地质约束条件，采用分层复原法对该区地质剖面进行平衡复原。复原结果表明，库车前陆冲断带南北向总缩短量为18～31km，缩短率为16％-34％。其中新生代变形强度最大，缩短率接近15％。新生代最强烈的构造变形又是发生在库车组开始沉积后的喜马拉雅运动晚期，该时期缩短量已超过新生代缩短量的80％，缩短速率达到2．43mm/a。

Compared with the restoration of balanced cross-sections in ordinary structural settings,the balancing of salt structural sections faces more difficulties because of the viscous flowage of salt bodies. It is addressed that the balanced cross-sections of salt structures,which are restored on the basis of the original thickness of salt layers and growth strata and triangles in the Kuqa foreland thrust belt in the northern part of Tarim Basin.The results reveal that the Paleogene Kumugeliemu Formation commenced depositing without spatial variations in original thickness of about 1,130m. The growth strata and triangles show that the strongest structural distortion of salt structures occurred during later Himalayan orogeny from the Kuqa period to Quaternary. Under the influence of SN-trending compressional stresses, the SN-trending shortening strains are 20-35 km and the shortening rates are 20%-35% in the Kuqa foreland thrust belt. On the whole, the differential structural distortion in varying structural belts,sectors and layers are obvious.The intense structural distortion in the supra-salt and subsalt strata happened in the Qiulitage and Kelasu structural belts,respectively. The salt layers acted as important detachment and harmonizer in the differential structural distortion.