榆林河地貌演化及其对阿尔金断裂扩展的响应

The Altyn Tagh Fault is a giant sinistral strike-slip fault in central Asia, and it controls the growth of the Tibetan Plateau as the northwest boundary. The thrust structures, the lateral propagation of the fault, are parallel or oblique to it on its two sides, and their profile shows a flower structure. The structure and landform of the Dunhuang Basin has been influenced deeply by the NW-trending propagation of the Altyn Tagh Fault. Our present proposal will focus on the quantitative study on the propagation of the Dongbatu Shan anticline-a reflection of the Altyn Tagh Fault propagation in the Dunhuang Basin. The fluvial landforms of the Yulin He have not been fully studied and we will therefore investigate and study the stream terraces, paleo-channel, lacustrine sediments and alluvial fans in detail in our present proposal. Based on the high resolution satellite images and combined with field geological survey and Quaternary dating techniques, the periodization and chronology of the fluvial geomorphology of the Yulin He are planned to be confirmed. We expect to build the relationship between the geomorphological evolution process of the Yulin He and the formation and extension of the Dongbatu Shan anticline, and analyse the space-time process of the geomorphological development and evolution of the Yulin He and Dongbatu Shan anticline. Furthermore, we will discuss how the formation and deformation of the landforms of the study area responded to the NW-trending propagation of the Altyn Tagh Fault.

阿尔金断裂是亚洲内部一条巨型左旋走滑断裂带，作为青藏高原西北边界的主控断裂控制着高原的生长。该断裂两侧分布着平行或斜交于它的逆冲构造，在剖面上呈花状构造样式，它们是阿尔金断裂的侧向扩展。敦煌盆地的构造和地貌受到阿尔金断裂NW向扩展的深刻影响。本申请以阿尔金断裂在敦煌盆地的扩展表现之一-东巴兔山背斜扩展的定量研究为切入点，重点选择研究程度较弱的榆林河河流地貌，以河流阶地、古河道及湖相沉积物、洪积地貌为研究对象。利用高分辨率卫星影像，结合野外地质调查和第四纪测年技术，确定榆林河河流地貌分期和年代序列。建立榆林河河流地貌演化过程与东巴兔山背斜的形成、扩展之间的关系，构建榆林河地貌与东巴兔山背斜的发育和演化时空过程，进而探讨该地区地貌形成和变形对阿尔金断裂北西向扩展过程的响应。

阿尔金断裂两侧分布着平行或斜交于它的逆冲构造，在剖面上呈花状构造样式，它们是阿尔金断裂的侧向扩展。敦煌盆地的构造和地貌受到阿尔金断裂NW向扩展的深刻影响。本项目以阿尔金断裂在敦煌盆地的扩展表现之一，东巴兔山背斜扩展的定量研究为切入点，重点选择研究程度较弱的榆林河河流地貌，以河流阶地、古河道及湖相沉积物、洪积地貌为研究对象，开展了地貌学、沉积学和年代学等工作。取得的初步认识主要如下：(1)东巴兔山顶上的古河道的阶地和河床形成年代分别为~160ka和80ka，表明河道废弃与80ka；(2)榆林河两侧Q2的洪积扇废弃于~160ka，并发育一系列晚更新世以来的阶地；(3) 东巴兔山北缘断层和南缘断层的滑动速率分别为0.1±0.009 mm/a和0.094~0.106 mm/a；(4)榆林河上游、中游和下游的的下切速率分别为0.63-1.42mm/a， 0.31-0.58mm/a，0.62-0.67mm/a；(5)阶地的形成主要受控于气候事件；(6)河道迁移受控于阿尔金扩展影响的东巴兔山山体隆升。