Post-6 Ma Tectonic Evolution of the Bhutan Himalaya

尽管过去几十年在碰撞山带进行了大量研究，但关于气候和构造过程对地表的影响，或者这些过程如何相互交织，几乎没有达成共识。最近在喜马拉雅中部--一个研究得很好的典型碰撞山带--对于什么是对地表过程最重要的控制产生了相互矛盾的观点。再往东，不丹喜马拉雅山脉还没有被详细研究过，但与经典的喜马拉雅山脉形态和地质学相比，经常被贴上离群点的标签。然而，不丹明显的反常特征使其成为检验有关气候、构造和地表过程相互作用的一些突出假设的绝佳环境。非典型的高海拔，但低起伏的景观栖息在不丹中纬度地区，并被切割得很深的峡谷所包围。这项研究探讨了这样一个命题，即这些地貌代表着席卷不丹并逐渐改变地貌的侵蚀脉冲。这种侵蚀脉冲标志着构造或气候的变化，或两者兼而有之，瞬变地貌的特征，特别是侵蚀速率的模式，为确定变化的驱动因素提供了一个框架。这一研究项目的重点是根据河沙中的宇宙源放射性核素浓度确定千年尺度的流域平均侵蚀率。抽样战略将涵盖广泛的年平均降雨量、河道陡度和流域起伏。通过将这些侵蚀速率与低温热年代学数据的约束相结合，研究小组将能够区分不丹的气候和构造驱动的模型，并测试关于气候、侵蚀速率、地形和构造之间的关系的假设，这些关系的影响远远超出不丹的现场。这项研究所述问题的积极性质涉及许多社会问题，包括：地震灾害、滑坡灾害、沉积、水库管理、通航能力、土壤侵蚀和对气候变化的反应。对于生活在世界各地活跃山脉或附近的人来说，这些问题有时是令人痛苦的清楚的。不丹，由于其复杂的政治历史和准入问题，是喜马拉雅地区最鲜为人知的地区之一。研究小组正在与不丹国家环境委员会密切合作，以有意义的方式分享调查结果，以便更好地为土地利用管理和减灾决策提供信息。此外，这项研究还解决了理解山地建筑的基本问题。碰撞背景下造山的许多经典模型都预测了断层活动的相对时间；然而，这些假设在某些地区被证明是失败的。广泛的样本收集计划将允许检查不丹各地的隆升模式，以确定这些经典模型是否适用。人们对不丹断层活动的历史知之甚少，因此，有关抬升模式的任何信息对不丹的理事机构来说都是非常宝贵的，因为它们决定了危险评估和控制建筑代码。

Despite the considerable amount of research conducted in collisional mountain belts over the past few decades, little consensus has been reached regarding the influence that climatic and tectonic processes have on the surface, or how these processes are intertwined. Recent studies in the central Himalaya - a well studied, archetypal collisional mountain belt - have produced conflicting ideas regarding what is the most significant control on surface processes. Farther to the east, the Bhutan Himalaya have not been studied in much detail, but are often labeled as an outlier when compared to the classic Himalayan form and geology. However, the apparently anomalous features of Bhutan make it an excellent environment to test some of the outstanding hypotheses regarding the interplay of climate, tectonics and surface processes. Atypical high-elevation, but low-relief landscapes are perched above and surrounded by deeply incised canyons in the middle latitudes of Bhutan. This study explores the proposition that these landforms represent a pulse of erosion that is sweeping through Bhutan and progressively changing the relief. Such a pulse of erosion signals a change in either tectonics or climate, or both and the characteristics of transient landscapes, including especially patterns of erosion rate, provide a framework to determine what the drivers for the change are. This research project focuses on determining basin-averaged millennial-scale erosion rates from the concentration of cosmogenic radionuclides within river sands. The sampling strategy will cover a wide range of mean annual precipitation, river channel steepness and basin relief. By combining these erosion rates with constraints from low-temperature thermochronology data, the research team will be able to discriminate between climate and tectonic-driven models in Bhutan and test hypotheses regarding the relationships between climate, erosion rate, topography and tectonics that carry implications well beyond the Bhutan field site.The active nature of the problem addressed in this research has ramifications for many societal concerns including: seismic hazards, landslide hazards, sedimentation, reservoir management, navigability, soil erosion, and response to climate change. These issues are at times painfully clear to those who live in or near active mountain ranges throughout the world. Bhutan, because of its complicated political history and access issues, is one of the most poorly understood regions of the Himalaya. The research team is working closely with the National Environmental Commission of Bhutan to share findings in a meaningful way that better informs decisions in land use management and hazard mitigation. In addition, this research tackles fundamental problems in the understanding of mountain building. Many of the classic models of mountain building in collisional settings make predictions about the relative timing of fault activity; however, these assumptions have been shown to fail in some areas. The broad sample collection scheme will allow examination of uplift patterns across Bhutan to determine if these classic models hold true. Very little is known about the history of fault activity in Bhutan and therefore, any information regarding the pattern of uplift is invaluable to the governing bodies of Bhutan, who determine hazard assessment and control building codes.