Post-6 Ma Tectonic Evolution of the Bhutan Himalaya

不丹喜马拉雅山6 Ma后构造演化

• 批准号: 1049888
• 负责人: Kelin Whipple
• 金额: $ 18.78万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2014-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1049888&HistoricalAwards=false
• 关键词: Post; Ma; Tectonic; Evolution; Bhutan

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.

尽管过去几十年来对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，尚未达成共识。最近对喜马拉雅山中部的研究——一个经过充分研究的典型碰撞山脉带——对于什么是对地表过程最重要的控制产生了相互矛盾的想法。再往东，不丹喜马拉雅山尚未得到详细研究，但与经典的喜马拉雅山形态和地质相比，经常被标记为异常值。然而，不丹明显的异常特征使其成为检验一些有关气候、构造和地表过程相互作用的杰出假设的绝佳环境。非典型的高海拔但低浮雕景观栖息在不丹中纬度地区的深切峡谷之上并被其包围。这项研究探讨了这样一个命题：这些地貌代表了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或两者的变化，瞬态景观的特征，特别是侵蚀速率的模式，提供了一个框架来确定变化的驱动因素。该研究项目的重点是根据河沙内宇宙源放射性核素的浓度确定流域平均千年尺度的侵蚀率。采样策略将涵盖广泛的年平均降水量、河道陡度和流域地形。通过将这些侵蚀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模型，并测试有关气候、侵蚀率、地形和构造之间关系的假设，这些假设具有很好的意义这项研究所解决的问题的活跃性质对许多社会问题产生了影响，包括：地震灾害、滑坡灾害、沉积、水库管理、适航性、土壤侵蚀和气候变化的响应。对于生活在世界各地活跃山脉中或附近的人们来说，这些问题有时是令人痛苦的清晰。由于其复杂的政治历史和准入问题，不丹是喜马拉雅山脉最不为人所知的地区之一。研究团队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研究结果，更好地为土地利用管理和减灾决策提供信息。此外，这项研究解决了理解造山的基本问题。许多碰撞背景下造山的经典模型都对断层活动的相对时间进行了预测。然而，这些假设在某些领域已被证明是不成立的。广泛的样本收集计划将允许检查不丹各地的隆起模式，以确定这些经典模型是否成立。人们对不丹断层活动的历史知之甚少，因此，任何有关隆起模式的信息对于不丹的管理机构来说都是非常宝贵的，他们负责确定危险评估和控制建筑规范。