西南天山新生代主要构造变形事件与沉积响应记录

The Cenozoic Tian Shan is one of the most excellent examples of an intracontinental orogen related to the India-Asia collision. The southwestern Tian Shan and its foreland basin constitue the unique tectonic landform of "Range-Basin" . This region represents the strongest tectonic deformation region along the Tian Shan.Thus,the Cenozoic tectonic deformation and sedimentary response in this region is a natural laboratory to understand the uplift processes of Tian Shan. In this study, we shall mainly focus on the tectonic deformation events and its sediemntary response.We shall map the tectonic deformations of the major thrust-and fold zones and klippe structures as well as the Cenozoic sedimentary sequences developed in the southwest Tian Shan and its foreland basin. A interdisciplinary study such as tectonic geomorphology, low-tempreature thermochronology, remote sensing and geochemistry will be used in order to constrian timing of the major tectonic deformation events, provenance analysis of key sedimentray sequences and their geologic ages. These ages, combined with tectnoic deformation and sedimentological data, will provide new evidence on the Cenozoic uplift processes of southwest Tian Shan. By comparing with data from different parts of the Tian Shan, it will be helpful to understand the geodynamics of uplift and formation for the Tian Shan during the Cenozoic.

西南天山及山前盆地构成了典型的山－盆构造特征，是天山新生代构造变形最强的地区，其新生代构造变形与沉积响应是研究天山新生代隆升过程的天然实验室。本研究以"主要构造变形事件及其沉积响应"为切入点，以西南天山主要逆冲褶皱带及飞来峰的构造变形以及前陆盆地数千米厚新生代的陆源碎屑岩为研究对象。拟通过遥感地质学、构造地貌学、低温热年代学和沉积学等学科手段来厘定西南天山主要构造变形事件的时间与前陆盆地主要砾岩的物源和形成时代。结合前期的研究成果，制约西南天山的新生代隆升的整体性和差异性，从而能更深刻地阐明天山造山带新生代复活的地球动力学机制。

本课题通过深入了解天山的新生代构造地质方面的研究现状和最新进展，获取了研究区的卫星遥感数据和数字高程资料，并对这些多源遥感数据进行处理和地质构造及地貌解译。在此基础之上，开展了六次野外考察和样品采集工作，并在实验室内进行低温热年代学（磷灰石裂变径迹）、碎屑锆石及宇宙核素埋藏年代学（10Be和26Al）分析方法，对研究区的构造变形时间与沉积物源进行约束。研究结果表明：西南天山及山前盆地的构造地貌生长具有自北向南逐渐向山前盆地方向扩展的特征，西南天山迈丹断裂构造活动于始新世末期(35-25 Ma)，而后15Ma左右构造活动向南扩展至木兹杜克断裂和阿图什盆地逆冲断裂，生长地层揭示阿图什盆地逆冲断裂以南的柯科塔木背斜的构造变形时间为6-3Ma, 最南侧的阿图什断裂-褶皱带的构造变形发生在2Ma左右。与此同时阿图什盆地新生代地层中至少发育三套厚层砾岩，其地质年代分别为：始新世-渐新世中期(39.9±9.7Ma），上新世（4.7Ma）和早更新世（1.7Ma），表明新生代以来西南天山前陆盆地至少发生三期重要的构造-气候事件。上述研究成果对于深入认识西南天山及山前盆地新生代“山-盆构造”地貌格局的形成过程及地球动力学机制具有重要科学价值。