Collaborative Research: What Created the Southern Tibetan Plateau Drainage Divide? Integrated Tectonic and Geomorphic Investigation of the Gangdese Range and Yarlung River

板块之间的碰撞运动使地壳变形，在数百万年的时间里形成了山带。这一过程在构造板块之间的边界上最为明显，但也发生在离板块边界更远的地方，那里更微妙的特征反映了更深层次的构造运动。这个项目的重点是西藏南部的冈底斯山脉，那里有青藏高原的一些最高的山脉。这些山脉位于喜马拉雅山脉最高峰以北200公里处，但由于与印度和亚洲构造板块碰撞有关的深部断裂作用，这些山脉正在积极上升。这条山脉形成了青藏高原低起伏、相对平坦的内陆和南部由雅鲁藏江-雅鲁藏布江-雅鲁藏布江排出的高起伏地区之间的边界。通过绘制地质结构图，确定岩石在地表暴露的时间和速度，并将这些数据与降雨和河流切割造成的侵蚀模拟进行比较，项目调查人员将确定深层构造运动的细节，以及这些运动如何影响青藏高原和亚洲最大的水系之一的景观。该项目的更广泛影响将包括在这项研究的基础上开发教学模块，为三名博士后和一名博士后研究员加入熟练的科学队伍做准备，以及通过博物馆主办的教学模块和公共研究演示向公众宣传。这项研究试图了解中新世至现代构造如何以及在多大程度上影响青藏高原南部的景观和水系。该项目将检验这一假说，即至少自中新世以来，冈底斯山脉之下的主要地壳斜坡或双重构造推动了喜马拉雅造山带内部沿高原南缘的岩石抬升。研究将集中于岩石抬升是否超过侵蚀，并建立排水分水岭，目前将广阔的内部排水地区与雅鲁藏布江-雅鲁藏布江-雅鲁藏布江水系南面分开。为了解决这一假说和其他替代假说，研究人员将进行一项综合研究，涉及现场构造地质学、热年代学、地貌演化建模和碎屑宇宙成因放射性核素测年。这些假设为岩石暴露的几何形状和变形历史、岩石冷却的时间和速率、对各种构造和/或气候驱动因素的预期地貌演变以及集水盆地千年尺度的侵蚀速率提供了一套可检验的预测。如果数据支持建立南部流域边界的构造驱动因素，那么构造也与雅鲁藏布江-雅鲁藏布江-雅鲁藏布江系统的演变有关，雅鲁藏布江是世界上最大的河流之一。这项研究将促进我们对山脉和高原如何形成对构造的响应，山脉景观如何演变并对不同的构造影响做出反应，以及主要水系如何在百万年到千年的时间尺度上发展的集体理解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Collisional motions between tectonic plates deform the Earth's crust, forming mountain belts over millions of years. This process is most visible along the boundaries between tectonic plates, but also occurs further away from plate boundaries, where more subtle features reflect deeper-seated tectonic movements. This project focuses on the Gangdese Mountains in southern Tibet, which host some of the highest mountains of the Tibetan Plateau. These mountains are located 200 kilometers north of the high peaks of the Himalayas, but are actively rising due to deep-seated faulting related to collision between the Indian and Asian tectonic plates. This range forms the boundary between the low-relief, relatively flat interior of the Tibetan Plateau that retains all precipitation in lakes, and the higher-relief region to the south that is drained by the Yarlung-Siang-Brahmaputra river. By mapping the geologic structures, determining when and at what rate rocks were exposed at the surface, and comparing these data to simulations of erosion due to precipitation and river incision, the project investigators will determine the details of the deep-seated tectonic motions and how these motions affected the landscape of the Tibetan Plateau and one of the largest river systems in Asia. Broader impacts of this project will include the development of teaching modules based on this research, the preparation of three PhD students and one postdoctoral researcher to join the skilled scientific workforce, and outreach to the public through museum-hosted instructional modules and public research presentations. This research seeks to understand how and to what extent Miocene to Recent tectonics affected the landscape and river systems of the southern Tibetan Plateau. The project will test the hypothesis that a major crustal ramp or duplex beneath the Gangdese Mountains drove rock uplift along the southern boundary of the Plateau, in the interior of the Himalayan orogenic belt, since at least Miocene time. Research will focus on whether rock uplift outpaced erosion and established the drainage divide that currently separates the expansive internally-drained region from the Yarlung-Siang-Brahmaputra river system to the south. To address this hypothesis and other alternative hypotheses, the researchers will conduct an integrated study involving field-focused structural geology, thermochronology, landscape evolution modeling, and detrital cosmogenic radionuclide dating. The hypotheses provide a set of testable predictions for the geometry of rock exposures and the history of deformation, timing and rates of rock cooling, expected landscape evolution in response to various tectonic and/or climatic drivers, and millennial-scale erosion rates for catchment basins. If a tectonic driver for establishment of the southern drainage boundary is supported by the data, then tectonics is also implicated in the evolution of the Yarlung-Siang-Brahmaputra River system, one of the largest in the world. This research will advance our collective understanding of how mountain belts and plateaus form in response to tectonics, how mountain landscapes evolve and respond to variable tectonic influences, and how major river systems develop during million-year to millennial timescales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.