Unlocking the Glacial History of the McMurdo Dry Valleys, Antarctica by Fingerprinting Glacial Tills with Detrital Zircon U-Pb Age Populations

这项研究的目的是识别和区分南极洲麦克默多干谷冰川沉积物的不同来源区域，以确定过去冰川流动的方向。了解冰流对于确定南极冰盖过去的行为至关重要。这种洞察力是让科学家预测南极冰盖将如何演变的基础，进而预测海平面可能上升的幅度和速度。该项目研究地点麦克默多干谷包含了至少1400万年前陆地上冰川沉积的巨大记录。冰川沉积物中岩石的化学成分提供了沉积物质的冰来源的线索。对冰川沉积物的化学分析将有助于绘制以前的冰川范围图，从而更好地了解冰川流动的历史。麦克默多干河谷过去1400万年来最大的冰盖扩张地图引起了全球气候变化界的广泛关注。本科生构成了实地小组的大多数，他们将负责实验室的样品准备和分析。该项目利用新的地球化学技术来测试有关南极麦克默多干谷(MDV)冰川冰块的来源、范围和流动模式的假说。MDV包含了无与伦比的冰川沉积的陆地档案，其中记录了沉积它们的多个冰源。其中包括覆盖在横跨南极山脉的东北流动冰、东南极冰盖的东延、罗斯冰架的西延，代表西南极冰盖的扩张，以及当地高山冰川的生长。南极的冰川耕作和漂流通常是以斑块或不连续的露头模式隔离的，这使得很难将冰耕相互关联并确定它们的来源。该项目将对麦克默多干河谷的碎屑进行系统研究，以利用各种地球化学技术确定其来源，包括X射线荧光主次元素分析、重矿物组成、土壤盐分浓度，以及测定这些碎屑中所含锆石砂的铀铅(U-铅)年龄。主要的工具将是冰川漂流中碎屑锆石群体的年龄分布，因为它反映了冰川碎屑的来源，并提供了一个独特的地球化学“指纹”，用于区分来源区域，同时将不同地点的单位进行对比。该项目的成果将是一个社区可用的锆石指纹库，用于从极地岩石储存库的存档样品中绘制冰川碎屑图，并在MDV中系统地收集样品。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this study is to identify and distinguish different source areas of glacial sediment in the McMurdo Dry Valleys, Antarctica to determine past glacial flow direction. Understanding ice flow is critical for determining how the Antarctic Ice Sheets have behaved in the past. Such insight is fundamental for allowing scientists to predict how the Antarctic Ice Sheets will evolve and, in turn, forecast how much and how fast sea level may rise. The project study site, the McMurdo Dry Valleys, contain a tremendous record of glacial deposits on land that extends back at least 14 million years. Chemistry of the rocks within the glacial deposits hold clues to the sources of ice that deposited the material. The chemical analyses of the glacial deposits will allow mapping of the former extent of glaciations providing a better understand of ice flow history. The mapping of the largest ice sheet expansion of the past 14 million years in the McMurdo Dry Valleys is of broad interest to the global climate change community. Undergraduate students comprise the majority of the field teams and will be responsible for sample preparation and analysis in the laboratory. This project utilizes new geochemical techniques to test hypotheses about the source, extent, and flow patterns of the glacier ice that deposited glacial tills in the McMurdo Dry Valleys, Antarctica (MDV). The MDV contain an unparalleled terrestrial archive of glacial deposits, which record multiple sources of ice that deposited them. These include the northeast flowing ice that overrode the Transantarctic Mountains, the eastward expansion of the East Antarctic Ice Sheet, the westward extension of the Ross Ice Shelf representing an expansion of the West Antarctic Ice Sheet, and the growth of local alpine glaciers. The glacial tills and drifts in the Antarctic are typically isolated in patches or disjointed outcrop patterns making it difficult to correlate tills and determine their source. This project will undertake a systematic study of the tills in the McMurdo Dry Valleys to determine their provenance with a variety of geochemical techniques including major and minor element analyses with X-ray fluorescence, heavy mineral composition, soil salt concentration, and determining the uranium-lead (U-Pb) ages of zircon sands contained in these tills. The primary tool will be the age distribution of the population of detrital zircon in a glacial drift because it reflects the source of the tills and provides a unique geochemical "fingerprint" used to distinguish source areas while correlating units across different sites. A deliverable from this project will be a community available library of zircon fingerprints for mapped glacial tills from archived samples at the Polar Rock Repository and the systematic collection of samples in the MDV.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.