Exploring the Early History of the South Tibetan Fault System in Bhutan

这项研究的重点是藏南断裂系统，喜马拉雅山最神秘的构造特征之一，在构造学界引起了很大的争议。藏南断层系统似乎是独特的，因为它的运动学是一个低角度的，正常的断层系统，而所有其他喜马拉雅断层系统具有可比的位移（许多10到100公里）具有更可预测的运动学逆冲断层系统通常发现在山区带。像藏南断层系统这样的特征的存在本身就表明了喜马拉雅山脉以及整个山脉如何演变的基本原理。PI和他的同事们通过他们的研究来澄清这一信息。不幸的是，在喜马拉雅山的许多地方，藏南断裂系统的早期历史已经被后期变形所掩盖。不丹的情况并非如此，在那里，PI和其他人已经确定了该系统早期断层的侵蚀遗迹，这些断层相对未受较新变形的影响。本提案介绍了对这些残留物进行的有针对性的研究。一系列广泛的技术将被用来探测使用这些罕见的曝光断层系统的早期历史。它们包括地质填图和结构分析;定量元素分配热压法; 40 Ar/39 Ar和（U-Th）/He热年代学;以及激光消融（U-Th）/Pb年代学。由于喜马拉雅山和青藏高原仍在发展，对这个天然实验室的研究提供了有关山区在地球系统功能中所起作用的关键信息。例如，我们知道青藏高原的自然地理定义了亚洲季风气候的天气模式，这种气候是农业的有利机制，养活了地球上大约60%的人。通过详细描述导致现代喜马拉雅山和青藏高原建立的过程，这里提出的研究为人类社会和山区景观的共同进化提供了更有效的战略。

This research focuses on the South Tibetan fault system, one of the most enigmatic tectonic features of the Himalaya, and one that stirs much controversy in the Tectonics community. The South Tibetan fault system appears to be unique in that its kinematics are those of a low-angle, normal fault system while all other Himalayan fault systems with comparable displacements (many 10s to 100s of kilometers) have the more predictable kinematics of thrust fault systems typically found in mountain belts. The very existence of a feature like the South Tibetan fault system is indicating something fundamental about how the Himalaya, and mountain ranges in general, evolve. The PI and his colleagues work to clarify this message through their research. Unfortunately, in many parts of the Himalaya, the early history of the South Tibetan fault system has been obscured by late-stage deformation. This is not the case in Bhutan, where the PI and others have identified erosional remnants of early faults of the system that have been relatively undisturbed by younger deformation. This proposal describes targeted studies of these remnants. A broad array of techniques will be used to probe the early history of the fault system using these rare exposures. They include geologic mapping and structural analysis; quantitative element-partitioning thermobarometry; 40Ar/39Ar and (U-Th)/He thermochronology; and laser-ablation (U-Th)/Pb geochronology. Because the Himalaya and Tibetan Plateau are still evolving, studies of this natural laboratory provide critical information regarding the role that mountainous regions play in earth system function. For example, we know that the physiography of the Tibetan Plateau defines the weather patterns of the Asian monsoon climate, and this climate is the enabling mechanism for agriculture that feeds roughly 60% of the people on Earth. By detailing the processes that led to the establishment of the modern-day Himalaya and Tibetan Plateau, studies such as the one proposed here inform more effective strategies for the co-evolution of human societies and mountain landscapes.