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，在较长的时间尺度内，侵蚀率变得更加稳定。这项研究假设降雨分布的空间变化调节侵蚀率的差异，并且特定的河流功率（流量和河道梯度的乘积）为现代侵蚀率提供了可靠的代表。该项目将使用非常高分辨率的降雨遥感数据以及数字地形来预测河流功率的变化。对侵蚀率的影响将通过对来自流域的样本进行宇宙成因核素（CRN）分析以及对比水流功率来评估。将使用热运动模型对流域横断面的各种矿物的冷却年龄进行分析，以可靠地重建较长时间尺度内侵蚀率的时间变化。喜马拉雅山脉位于活跃的构造区域，该提案提出了这样的假设：由于构造板块的持续碰撞，地形发生横向平流。据推测，这种平流会导致喜马拉雅河流域和相关地形的重大重组。由于平流导致溪流捕获并形成新的跨喜马拉雅河流，侵蚀力大大增强，其他干流河道将被斩首，从而失去动力。河流功率的这种变化应该通过侵蚀率和地形起伏的变化来表达。该项目将通过使用地势断面和等高断面的基岩冷却年龄重建地形地貌的变化来测试这些想法。该项目的重点是山带如何生长和腐烂，以及气候调节的侵蚀如何影响其中发生地震的地点。最近的理论表明，在积极变形的山带中，降雨的空间变化模式会导致侵蚀速率的差异，而这些侵蚀差异会影响变形发生的位置。喜马拉雅山拥有强烈的季风降雨、大面积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。卫星数据地面观测显示，喜马拉雅山脉的长度和宽度上的降雨量都发生了突变。通过将降雨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侵蚀应该快速或缓慢的地方。当前喜马拉雅山沿线降雨量的空间变化大部分是由横穿喜马拉雅山的大河谷的作用造成的：它们提供了引导降水进入山脉的地形通道，从而似乎或多或少地影响了侵蚀的地方激烈的。该提案认为，这些山谷并不是永久锁定的，但它们可以移动和改变排水模式。现场和实验室调查将记录侵蚀率随时间的变化以及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水。这项工作将提供有关偏远地区（目前鲜为人知）的降雨、降雪和水平衡的见解，并将有助于更好地预测河流的动态，这对印度和尼泊尔人民来说是一项重大利益。