Collaborative Research: Glacial Erosion in the Patagonian Andes: Testing the Buzzsaw

合作研究：巴塔哥尼亚安第斯山脉的冰川侵蚀：测试圆锯

• 批准号: 0447140
• 负责人: Stuart Thomson
• 金额: $ 29.4万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0447140&HistoricalAwards=false
• 关键词: Collaborative; Research; Glacial; Erosion; Patagonian

The remarkable match between the glacial equilibrium line altitude (ELA) and summit elevations in many active mountain ranges of the world has led to the supposition that glaciers act as an erosional buzzsaw. Since most observed rates of glacial erosion are very high they are thought to be able to effectively remove most topography tectonically uplifted through the ELA. However, the glacial buzzsaw idea is based largely on circumstantial evidence. Only preliminary attempts have been made to theoretically simulate quantitative predictions of this process. This proposed research aims to test the glacial buzzsaw hypothesis using modern technical and computational methods. Understanding the importance of glacial erosion is complicated by the fact that elevated topographies are often the result of plate convergence, and so an appreciation of the feedbacks involved between orogenic wedge mechanics and surface processes is required. Development of a coupled geodynamic and surface process model that incorporates glacial erosion in an active critical orogenic wedge is proposed to examine these feedbacks. Preliminary model predictions indicate that the temporal and spatial patterns of uplift and erosion for both a weak and strong glacial buzzsaw in an active orogen contrast significantly with erosion patterns of an orogen that responds to the buzzsaw by passive isostasy. Testing the model predictions to judge whether glacial erosion acts as a 'strong' or 'weak' buzzsaw will be achieved by applying combined apatite (U-Th)/He and fission-track low temperature thermochronology to evaluate changes in erosion rates and spatial erosion patterns following the onset of late Cenozoic glaciation in the Patagonian Andes - the orogen where the match between the height of the ELA and summit elevation was first recognized. The Patagonian Andes are an exceptional natural laboratory. As well as having a suitable and well-documented tectonic and climatic history, their north-south range provides an opportunity to study a spatially varying glacial history. Two different transects will be targeted: one at 39S to 41S (Valdivia, Pucn, Bariloche), and another between 46S and 51S (Canal Baker, Lago General Carrera, South Patagonian Icefield). This will include the collection of both near-vertical and trans-orogen sample profiles. The proposed work will address the following research questions: 1) Does the glacial buzzsaw hypothesis explain the behavior of surface erosion in the Patagonian Andes? 2) Was the buzzsaw diachronous or synchronous along the length of the Patagonian Andes? 3) Is the orogen close to steady state, or still responding to the drop in ELA? and 4) How accurate are current models of glacial erosion over regional scales and long time periods?Broader ImpactThe long-term behavior of the earth system is dependent on dynamic interactions between climate, albedo, tectonics, orogenic topography, weathering, and greenhouse gases, such as CO2. In particular, there has been much speculation about the role that erosional fluxes from orogenic landscapes might play in moderating the greenhouse effect, given the important role of silicate weathering in moderating CO2 concentrations in the atmosphere. Orogenic topography as influences the distribution of precipitation, and can also change global atmospheric circulation, if the topography gets high enough, as is presently the case in the Himalaya and central Andes. Thus, there remains broad interest in the factors that might influence the evolution of orogenic topography, or limit the maximum size of the topography. This research will make a significant contribution towards understanding the role that alpine glaciation plays in controlling the maximum height of mountain ranges. The multidisciplinary approach of this proposal will foster a number of national and international educational and research links. Students and researchers from Louisiana State, Yale, GFZ Potsdam, the Universidad de Chile will be involved in this project. Students from two US institutions will have an opportunity to combine field research and theory. The proposed study has the potential to provide research support for an alumnus of the NSF funded Geoscience Alliance to Enhance Minority Participation in the Earth Sciences (GAEMP) project, through co-PI JonathanTomkin's participation in the program at LSU. The results of the research will be integrated into a GAEMP summer school program, which emphasizes the value of ongoing earth science research to minority undergraduates.This award is being supported with funds from the Geomorphology and Land Use Dynamics Program, the Tectonics Program, and the Americas Program in the Office of International Science and Engineering.

世界上许多活动山脉的冰川平衡线高度（ELA）和山顶高度之间的显著匹配导致了冰川作为侵蚀电锯的假设。由于大多数观测到的冰川侵蚀速率非常高，它们被认为能够有效地消除大部分通过ELA构造抬升的地形。然而，冰川电锯的想法主要是基于间接证据。只有初步的尝试已作出理论模拟定量预测这一进程。这项拟议中的研究旨在使用现代技术和计算方法来测试冰川电锯假说。认识冰川侵蚀的重要性是复杂的事实，升高的地形往往是板块会聚的结果，因此，需要了解造山楔力学和表面过程之间的反馈。耦合地球动力学和表面过程模型，结合冰川侵蚀在一个活跃的关键造山楔的发展，建议检查这些反馈。初步的模型预测表明，时间和空间模式的隆起和侵蚀的弱和强的冰川buzzsaw在一个活跃的造山带对比显着的侵蚀模式的造山带，响应buzzsaw的被动等值线。通过应用磷灰石（U-Th）/He和裂变径迹低温热年代学来评估巴塔哥尼亚安第斯山脉晚新生代冰川作用开始后侵蚀速率和空间侵蚀模式的变化，来测试模型预测，以判断冰川侵蚀是“强”还是“弱"。首次发现ELA高度与峰顶高程匹配的造山带。巴塔哥尼亚的安第斯山脉是一个特殊的自然实验室。除了具有适当的和有据可查的构造和气候历史外，它们的南北分布范围为研究空间变化的冰川历史提供了机会。将针对两个不同的断面：一个在39 S至41 S（Valdivia，Pucn，Bariloche），另一个在46 S和51 S之间（Canal Baker，Lago General Carrera，South Patagonian Icefield）。这将包括收集近垂直和跨造山带的样品剖面。拟议的工作将解决以下研究问题：1）冰川电锯假说是否解释了巴塔哥尼亚安第斯山脉表面侵蚀的行为？2)沿着巴塔哥尼亚安第斯山脉的长度，电锯是历时的还是同步的？3)造山带是接近稳定状态，还是仍然对ELA的下降做出反应？4）目前的冰川侵蚀模型在区域尺度和长时间内的准确性如何？更广泛的影响地球系统的长期行为取决于气候、地壳运动、构造、造山地形、风化和温室气体（如二氧化碳）之间的动态相互作用。特别是，有很多猜测的作用，从造山景观侵蚀通量可能发挥缓和温室效应，在缓和大气中的二氧化碳浓度的硅酸盐风化的重要作用。造山带地形影响降水的分布，如果地形足够高，也可以改变全球大气环流，就像喜马拉雅山和安第斯山脉中部目前的情况一样。因此，人们对可能影响造山地形演化或限制地形最大规模的因素仍有广泛的兴趣。这项研究将对了解高山冰川作用在控制山脉最大高度方面的作用做出重大贡献。这项建议的多学科方法将促进一些国家和国际教育和研究联系。来自路易斯安那州、耶鲁大学、GFZ波茨坦、智利大学的学生和研究人员将参与该项目。来自两所美国机构的学生将有机会将联合收割机的实地研究和理论结合起来。拟议的研究有可能通过共同PI JonathanTomkin参与路易斯安那州立大学的计划，为NSF资助的地球科学联盟的校友提供研究支持，以加强少数民族参与地球科学（GAEMP）项目。该研究成果将被纳入GAEMP暑期学校计划，该计划强调正在进行的地球科学研究对少数民族本科生的价值。该奖项由国际科学与工程办公室的地貌学和土地利用动力学计划，构造计划和美洲计划提供资金支持。