The Pamir Frontal Thrust System: Rates, Style, and Controls on Deformation

该项目重点关注位于中国最西部帕米尔高原和天山交界的结构走廊。这两个相对的造山带逐渐相互碰撞，在它们之间，困住了该地区最大的河流，克孜勒苏河。在一个空间紧凑的区域，各种各样的构造和不同的变形机制有利于快速收敛，包括低角度逆冲断层、逆断层、褶皱陡坡、褶皱和弯曲滑动断层。帕米尔锋面逆冲系统在紧邻克孜勒苏河的地方，是帕米尔造山带的前缘，在其他地方，主断层位于距离克孜勒苏河数公里的地方。这种沿走向的可变性提供了一个机会来评估有效的河流侵蚀可以集中变形的概念。离轴向河流越远，越快的变形速率将倾向于否定侵蚀-变形假说。在天山南缘靠近克孜勒苏的地方，与更远的地方相比，结构的加速速率支持侵蚀变形假说。为了确定变形率，研究小组将：利用InSAR在年代际尺度上描绘区域变形模式；利用光激发发光法测定地表断裂活动断层；利用光激发发光、宇宙成因放射性核素和放射性碳方法测定台地和扇的变形；利用磁地层学和(U-Th)/He测年确定长期滑动速率；并利用地震剖面来约束地下结构。尽管许多数值模型预测了集中侵蚀促进局部和加速变形这一概念上很有吸引力的观点，但很少有明确的案例研究证明了这种联系。这项在帕米尔高原-天山的研究可能为侵蚀和变形之间的联系提供明确的实地证据，因为该地区有许多有利的属性，应该允许对河流系统的变形模式和速率进行明确的评估。除了提供对山带动力学的洞察和评估流行的构造地貌学范式之外，对几个大型活动断层的古地震分析将提高对这些断层所造成的地震危害的理解，其中一些断层已经产生了致命的地震。最后，该项目将涉及与中国科学家的实质性合作，为研究生和本科生提供研究机会，并与学校和博物馆进行接触。

This project focuses on the structural corridor that lies at the interface between the Pamirs and the Tian Shan in westernmost China. These two, oppositely facing orogens are progressively impinging on each other, and between them, have trapped the largest river in the region, the Kezilesu. Across a spatially compact zone, a diverse array of structures and contrasting deformation mechanisms accommodate rapid convergence, including low-angle thrust faults, reverse faults, fold scarps, folds, and flexural slip faults. Representing the leading edge of the Pamir orogenic wedge, the Pamir Frontal Thrust system is in places immediately adjacent to the Kezilesu River and at others the primary fault lies many kilometers from the river. This along-strike variability provides an opportunity to assess the concept that efficient fluvial erosion can focus deformation. Faster deformation rates farther from the axial river would tend to negate the erosion-deformation hypothesis. Accelerated rates on structures across the southern margin of the Tian Shan that are proximal to the Kezilesu compared to more distal sites would support the erosion-deformation hypothesis. To determine deformation rates, the research team will: delineate regional patterns of deformation at decadal time scales using InSAR; date active surface-rupturing faults using optically stimulated luminescence methods; date deformation of terraces and fans using optically stimulated luminescence, cosmogenic radionuclide, and radiocarbon methods; determine long term slip-rates using magnetostratigraphy and (U-Th)/He dates; and use seismic sections to constrain subsurface structure.The role of active erosion in modulating deformation is still actively debated Whereas the conceptually attractive idea that focused erosion promotes localized and accelerated deformation is predicted by many numerical models very few unequivocal case studies exist that demonstrate such a linkage. This study in the Pamir-Tian Shan may provide unequivocal field evidence for a linkage between erosion and deformation because the region has many favorable attributes that should permit a clear assessment of the pattern and rate of deformation with respect to the river system. In addition to providing insight on the dynamics of mountain belts and assessing a popular tectonic geomorphology paradigm, paleoseismic analysis of several large active faults will improve understanding of the seismic hazards posed by these faults, some of which have produced deadly, recent earthquakes. Finally, the project will involve substantial collaboration with Chinese scientists, research opportunities for graduate and undergraduate students, and outreach to schools and museums.