Climatic and Tectonic Insights from Low-Temperature Thermochronometry Across the Himalayan Rain Shadow, Everest Region, Nepal and Tibet

喜马拉雅雨影区、珠穆朗玛峰地区、尼泊尔和西藏的低温测时法对气候和构造的见解

• 批准号: 1346360
• 负责人: Kip Hodges
• 金额: $ 24.58万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1346360&HistoricalAwards=false
• 关键词: Climatic; Tectonic; Insights; Low; Temperature

The physiographic transition from the Gangetic Plains to the Tibetan Plateau corresponds in space to one of our planet's most profound climate transitions. Several popular geodynamic models for the late Cenozoic evolution of the Himalaya feature a strong feedback relationship between precipitation, erosional rock exhumation, and deformation. If valid, these models predict that the extreme precipitation gradient across the Himalaya should be accompanied by variations in denudation rate and deformational patterns. Previous studies along the southern Himalayan flank conducted to verify these predictions have had mixed results, partly because they were done along the valleys of major rivers that cut across the Himalaya. These 'Transhimalayan' river valleys serve as pathways for northern penetration of monsoon storms, such that erosion rates on either side of the range crest may not truly reflect potential effects of the rain shadow. In addition, extreme incision of the Transhimalayan rivers during uplift of the Himalaya may focus exhumation and obscure broader patterns related to climate and regional tectonics. We endeavor to learn more about exhumation patterns across the rain shadow by applying the (Uranium-Thorium)/Helium thermochronometer to rocks collected along a transect that does not follow a Transhimalayan river. Nearly three decades of research in in the Everest region of central Nepal and southern Tibet by several researcher groups has resulted in an unusually good understanding of the basic structural geology of the region, permitting interpretation of the data obtained in appropriate structural context. Our goal is a comprehensive dataset suitable for thermal-kinematic modeling aimed at providing an improved understanding of the coupled influence of precipitation and dynamics of Himalayan orogenic wedge. We are also taking advantage of a portion of the data produced to explore the timing and slip history of the Lhotse and Qomolangma detachments in the Rongbuk Valley north of Mount Everest. These are two of the best studied of all strands of the South Tibetan detachment system, a major tectonic feature in the Himalaya. While the South Tibetan detachment system is known to have been active throughout the Himalaya in Early to Middle Miocene time, the actual age of youngest movement is poorly constrained in most areas, including the Rongbuk Valley. We are providing new constraints on the low-temperature thermal structure of the footwalls of the two detachments here through (Uranium-Thorium)/Helium and fission track work on accessory minerals. Exposures of the detachments in the Rongbuk Valley are unusual: shallow fault dip angles and high relief conspire to provide sampling opportunities over as distance of greater than 35 kilometers in the direction of transport in the immediate footwall of the South Tibetan detachment system. While much research focuses on the global impacts of climate variations in space and time, some of the greatest frontiers for research are at smaller, regional scales. On those scales, we are addressing questions about how climate variations relate to other natural earth system processes. Of particular interest for this study is how mountain ranges affect local climate and, conversely, how local climate can influence the erosional history of a mountain range. The high mountain ranges of the Himalaya retard the northward track of the South Asian monsoon system, creating two very different landscapes: the heavily forested slopes of the southern Himalayan flank, which receive some of the highest recorded annual rainfall totals on earth, and the high deserts of the southern Tibetan Plateau. Our work is aimed at understanding how far back in time this climatic pattern may have extended and how it might cause variations in erosion rate north and south of the Himalayan crest. The lessons learned here will inform perceptions of the role of regional climate variation in the erosional process both in the United States and abroad. The project is supporting a talented female Ph.D. candidate, thereby contributing to on-going efforts to reduce the gender disparity between male and female doctoral level scientists, a problem that is particularly acute in the physical sciences. In addition, special multimedia displays are being created for public museum exhibitions exploring the science of climate variations in mountainous landscapes.

从恒河平原到藏族高原的物理学转变在太空中对应于我们星球最深刻的气候过渡之一。喜马拉雅山晚期的几种流行的地球动力学模型在降水，侵蚀岩石挖掘和变形之间具有牢固的反馈关系。如果有效，这些模型预测，喜马拉雅山的极端降水梯度应伴随着剥离率和变形模式的变化。先前在喜马拉雅南部侧面进行的研究以验证这些预测的结果不同，部分原因是它们沿着横跨喜马拉雅山的主要河流的山谷进行。这些“ Transhimalayan”河谷是季风风暴北部渗透的途径，因此，山峰两侧的侵蚀率可能并不能真正反映出雨影的潜在影响。此外，喜马拉雅河上升期间，跨性河河的极端切割可能会集中挖掘，并掩盖与气候和地区构造有关的更广泛的模式。 我们努力通过将（铀thorium）/氦气热量器应用于不遵循Transhimalayan河的样带收集的岩石，以了解有关雨阴影中挖掘模式的更多信息。几个研究人员组成的尼泊尔中部和西藏中部珠穆朗玛峰地区的近三十年的研究已经对该地区的基本结构地质进行了异常的了解，从而可以解释在适当的结构环境中获得的数据。我们的目标是一个适合热模型建模的综合数据集，旨在提高对喜马拉雅造影质楔的降水和动力学影响的耦合影响。我们还利用了一部分数据来探索珠穆朗玛峰以北的Rongbuk山谷的Lhotse和Qomolangma支队的时机和滑移历史。这是南藏族分队系统的所有链中最好的两个研究，这是喜马拉雅山中的主要构造特征。虽然众所周知，南藏族支队在中新世的早期至中期一直活跃于整个喜马拉雅山，但最年轻的运动的实际年龄在包括朗布克山谷在内的大多数地区受到限制。我们通过（铀 - 硫群）/氦气和辅助矿物质的疗程进行了两个分离板的脚壁的低温热结构的新约束。隆布克山谷中的支队的暴露是不寻常的：浅断层倾角和高浮雕共谋，在南藏族脱离系统的直接泳衣中，在运输方向上提供了超过35公里的抽样机会。尽管许多研究重点介绍了气候变化在时空的全球影响，但一些最伟大的研究领域是在较小的区域尺度上。在这些尺度上，我们正在解决有关气候变化与其他自然地球系统过程如何相关的问题。这项研究特别感兴趣的是山区范围如何影响当地的气候，相反，当地气候如何影响山脉的侵蚀历史。喜马拉雅山的高山山脉阻碍了南亚季风系统的北向轨道，创造了两个截然不同的景观：喜马拉雅南部侧面的森林森林山坡，在地球上获得了一些最高记录的年度降雨量，以及藏族南部高原的高沙漠。 我们的工作旨在了解这种气候模式可能已经延长了多远，以及如何导致喜马拉雅波峰北部和南部的侵蚀率变化。这里学到的经验教训将为美国和国外的区域气候变化在侵蚀过程中的作用提供看法。该项目正在支持有才华的女性博士学位。候选人，从而为减少男性和女性博士学位科学家之间的性别差异做出了努力，这在物理科学中尤为严重。 此外，正在为公共博物馆展览创建特殊的多媒体展览，探索山区景观中气候变化的科学。