Collaborative Research: Orogeny, orography, and unsteady erosion: evolution of the Himalaya

合作研究：造山运动、地形和不稳定侵蚀：喜马拉雅山的演化

• 批准号: 0819709
• 负责人: Jeremy Hourigan
• 金额: $ 18.03万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0819709&HistoricalAwards=false
• 关键词: Collaborative; Research; Orogeny; orography; unsteady

This research attempts to understand how Himalayan rates of erosion vary as a function of space and time. Some initial data suggest that erosion rates become much steadier at longer time scales. This research hypothesizes that spatial variations in rainfall distributions modulate differences in erosion rates and that specific stream power (the product of discharge and channel gradient) provides a reliable proxy for modern erosion rates. This project will use very high resolution remote-sensing data on rainfall along with digital topography to predict variations in stream power. The effect on erosion rates will be evaluated through cosmogenic nuclide (CRN)analyses of samples from catchments with contrasting stream power. Cooling ages of various minerals from transects in the catchments will be analyzed using thermokinematic models to create reliable reconstructions of temporal changes in erosion rates over longer time scales. The Himalayas are in an active tectonic region, and the proposal presents the hypothesis that topography advects laterally in response to the ongoing collision of tectonic plates. This advection is hypothesized to cause major re-organization of Himalayan drainages and related topography. As advection leads to stream capture and creation of new Transhimalayan rivers with greatly enhanced erosive power, other trunk channels will be beheaded, thereby losing power. Such changes in stream power should be expressed by changes in both erosion rates and topographic relief. The project will test these ideas by reconstructing changes in topographic relief using bedrock cooling ages both from their relief transects and from equal-elevation transects. This project focuses on how mountain belts grow and decay and how climatically modulated erosion may affect where earthquakes occur within them. Recent theory suggests that, in actively deforming mountain belts, spatially varying patterns of rainfall cause contrasts in erosion rates and that these differences in erosion influence where deformation occurs. The Himalayas, with their strong monsoonal rains, large-scale topography, and rapid rates of tectonic deformation, are an ideal setting in which to explore these proposed interactions. Satellite data ground-based observation reveal that the amount of rainfall changes abruptly both along the length and breadth of the Himalaya range. By combining the rainfall data with the topography of the Himalaya, this project's numerical models will predict where erosion should be rapid or slow. Much of the current spatial variation in rainfall along the Himalaya appears to result from the role of large river valleys that slice across the Himalaya: they provide topographic conduits that guide precipitation into the mountains and, thereby, appear to influence where erosion is more or less intense. This proposal contends that these valleys are not permanently locked in place, but they can shift and change drainage patterns. The field and laboratory investigation will document changes in erosion rates through time and changes in the topography of the Himalaya. Over 300 million people live downstream from the Himalaya and utilize the waters that flow from it. This work will provide insight on rainfall, snow, and water balance in remote (and currently poorly known) areas, and it will help facilitate better forecasting of river behavior, a significant benefit for the people of India and Nepal.

这项研究试图了解喜马拉雅山脉的侵蚀率如何随着空间和时间的变化而变化。一些初步数据表明，侵蚀率在较长的时间尺度上变得更加缓慢。本研究假设，降雨分布的空间变化调节侵蚀速率的差异和特定的流功率（流量和通道梯度的产品）提供了一个可靠的代理现代侵蚀速率。该项目将使用非常高分辨率的降雨遥感数据沿着数字地形，以预测水流功率的变化。将通过对来自具有对比水流功率的集水区的样本进行宇宙成因核素（CRN）分析来评估对侵蚀率的影响。将使用热动力学模型分析集水区断面中各种矿物的冷却年龄，以建立更长时间尺度上侵蚀率随时间变化的可靠重建。喜马拉雅山位于一个活跃的构造区，该提案提出了一个假设，即由于构造板块的不断碰撞，地形横向平流。这种平流被假设为导致喜马拉雅水系和相关地形的重大重组。由于平流导致河流被捕获，并产生了新的具有极大增强侵蚀力的Transimalayan河流，其他主干河道将被切断，从而失去动力。这种水流动力的变化应该用侵蚀率和地形起伏的变化来表示。该项目将测试这些想法，重建地形起伏的变化，使用基岩冷却年龄从他们的救济样带和等高样带。该项目的重点是山区带如何生长和衰退，以及气候调节的侵蚀如何影响其中发生地震的地方。最近的理论表明，在积极变形的山区地带，降雨的空间变化模式造成侵蚀率的对比，这些差异侵蚀影响变形发生的地方。喜马拉雅山脉有着强烈的季风雨、大规模的地形和快速的构造变形，是探索这些相互作用的理想环境。地面观测的卫星数据显示，降雨量沿喜马拉雅山脉的长度和宽度沿着都有突变。通过将降雨量数据与喜马拉雅山的地形相结合，该项目的数值模型将预测哪里的侵蚀应该是快速或缓慢的。目前沿喜马拉雅沿着降雨量的空间变化似乎主要是由于横贯喜马拉雅的大河谷的作用：它们提供了地形上的通道，引导降水进入山区，从而似乎影响了侵蚀或多或少的强度。该提案认为，这些山谷并不是永久固定的，但它们可以移动和改变排水模式。实地和实验室调查将记录侵蚀率随时间的变化和喜马拉雅山地形的变化。超过3亿人生活在喜马拉雅山下游，并利用从喜马拉雅山流出的沃茨。这项工作将提供偏远地区（目前知之甚少）降雨、降雪和水平衡的洞察力，并有助于更好地预测河流的行为，这对印度和尼泊尔人民来说是一个巨大的好处。