南天山造山带的同碰撞和碰撞后构造——塔里木盆地北部地震解释成果

南天山位于中亚造山带的南缘，是一条增生—碰撞型造山带。其碰撞造山的时间，是中亚造山带研究的一个关键构造问题，引起广泛的关注。以往关于碰撞造山的时间证据，基本上都来自造山带自身，即南天山前新生界露头区。前陆区广泛覆盖着巨厚的新生界，无法直接考察，很少从前陆区碰撞相关构造的角度研究南天山碰撞造山的时间。塔里木盆地北部是南天山碰撞造山带的前陆区。经认真系统地解释这里的地震资料，发现了南天山碰撞造山带的同碰撞构造和碰撞后构造。同碰撞造构造由二叠纪末—三叠纪冲断层及其相关褶皱组成。三叠系/二叠系和侏罗系/三叠系两个不整合给出了二叠纪末—三叠纪初和三叠纪末—侏罗纪初两期挤压冲断的时间。造山后构造为侏罗纪—白垩纪正断层组成。正断层活动起始于三叠纪末—侏罗纪初，持续至白垩纪中期。根据同碰撞构造和碰撞后构造的形成时间推论，南天山碰撞造山作用起始于二叠纪末，结束于三叠纪末；侏罗纪—白垩纪中期为造山后应力松弛构造演化阶段。

Syn- and post-collision structures of the South Tianshan orogenic belt: Results of the seismic interpretation in the northern Tarim Basin along the South Tianshan

The South Tianshan on the southern margin of the central Asian orogenic belt （CAOB） is a complicated accretionary-collisional orogenic belt. The final collision occured between the Tarim continent and Ili-central Tianshan volcanic arc. The initial time of the collision is a significant for the CAOB tectonics and remains debated. Almost all the previous studies on it were carried out within the South Tianshan Mountains, few within the related basins covered with think Cenozoic deposits. The northern Tarim Basin along the South Tianshan is the foreland of the South Tianshan orogenic belt. Both syn- and post-collision structures were discovered there after careful and systematic seismic interpretation. The syn-collision structures are the End Permian-Triassic thrusts. They are fairly seen as the syn-collision compressional structures of the South Tianshan collisional orogen. Timed with the Triassic/Permian and Jurassic/Triassic unconformities, there are two thrusting phases occurred at End Permian-beginning Triassic and End Triassic-beginning Jurassic, respectively. The post-collision structures are the Jurassic-Cretaceous normal faults. According to the growth indexes, the normal faulting began at beginning Jurassic, lasted to Middle Cretaceous and then ceased. On the basis of these observed syn- and post-collision structures, it can be fairly inferred that the collision between Tarim and Ili-central Tianshan initiated at End Permian, lasted in Triassic and ceased at End Triassic, and then evolved into the Jurassic-Middle Cretaceous extensional tectonic stage.