Collaborative Research: The Pleistocene Erosion History of Glaciated Alpine Valleys Interrogated by Apatite 4He/3He Thermochronometry

这项研究将在不列颠哥伦比亚省的海岸山脉和新西兰的南阿尔卑斯山（峡湾地区）这两个巨大的沿海中纬度山脉内重建侵蚀和地形形成的详细历史。深而广的高山峡谷是第四纪冰川作用最壮观的遗产之一。但是，关于这些山谷中侵蚀和地形发展的总规模和时空格局的具体资料很少。然而，这些山谷的侵蚀和地形的发展对形成主要山脉的侵蚀、气候和构造耦合系统的演变至关重要。在数百万年的时间尺度和小于2公里的挖掘厚度上获得这种山谷发育的定量信息，将对解决晚新生代向冰川气候过渡是否伴随着山谷切割速率的增加和地形的增加这一问题作出重大贡献。这项研究将首次系统地应用一种非常有前途的新型地球化学工具——磷灰石4He/3He热时计。这项技术与传统的热时计方法有着根本的不同，因为它对独特低温的敏感性以及从单一矿物颗粒中得出冷却历史的能力。研究结果将与全球气候变化的历史联系起来，并沿山谷网络的纵轴变化的特征模式。该研究将确立一种新的地球化学技术的实用性，该技术在地表过程研究和构造学中具有广泛应用的潜力。该项目将构成初级PI研究计划的重要组成部分，并将成为他的新惰性气体热时计实验室设备的首批科学应用之一。建议的工作将构成研究生博士研究和训练的重要组成部分，并将在本科课堂上作为案例研究。

This research will reconstruct detailed histories of erosion and relief generation at locations within two great coastal mid-latitude mountain ranges, the Coast Mountains of British Columbia and the Southern Alps (Fiordlands region) of New Zealand. Deep and broadly scoured alpine valleys are one of the most spectacular legacies of Quaternary glaciation. However, very little specific information is available about the total magnitudes and the temporal and spatial patterns of erosion and relief development in these valleys. Yet erosion and relief development of these valleys is central to the evolution of the coupled system of erosion, climate, and tectonics that shapes major mountain ranges. Acquiring quantitative information about such valley development over timescales of a few million years and exhumation thicknesses of less than 2 km will be a major contribution toward resolving the question of whether the late Cenozoic transition to glacial climate was accompanied by increased valley incision rates and increased relief generation. This research will be the first systematic application of a very promising new geochemical tool, apatite 4He/3He thermochronometry. This technique is fundamentally different from conventional thermochronometric methods in its sensitivity to uniquely low temperatures and its ability to derive cooling histories from single mineral grains. Results will be examined for connections to the history of global climate change and for characteristic patterns of variation along the longitudinal axes of valley networks. The research will establish the usefulness of a new geochemical technique that has the potential for widespread applications in surface process studies and tectonics. The project will constitute an important part of the research program for a junior PI, and will be one of the first scientific applications of his new noble gas thermochronometry laboratory facility. The proposed work will constitute an important part of a graduate student's doctoral research and training, and will be used as a case study in undergraduate classes.