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

通过用碎屑锆石 U-Pb 年龄种群对冰川碴进行指纹识别，解开南极洲麦克默多干谷的冰川历史

• 批准号: 1842542
• 负责人: Daniel Morgan
• 金额: $ 42.74万
• 依托单位: Vanderbilt University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1842542&HistoricalAwards=false
• 关键词: Unlocking; Glacial; History; McMurdo; Dry

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.

本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源区，以确定过去的冰川流动方向。了解冰流对于确定南极冰盖过去的行为至关重要。这样的洞察力是科学家预测南极冰盖将如何演变的基础，反过来，预测海平面上升的幅度和速度。该项目的研究地点是麦克默多干谷，它包含了至少1400万年前陆地上冰川沉积物的大量记录。冰川沉积物中岩石的化学成分为沉积物质的冰的来源提供了线索。对冰川沉积物的化学分析将有助于绘制以前冰川作用范围的地图，从而更好地了解冰流历史。绘制麦克默多干旱山谷过去1400万年来最大的冰盖扩张图对全球气候变化界具有广泛的意义。本科生组成了大部分的现场团队，并将负责样品制备和分析在实验室。该项目利用新的地球化学技术来测试有关南极洲麦克默多干谷冰川冰碛物沉积的冰川冰的来源、范围和流动模式的假设。MDV包含了一个无与伦比的冰川沉积物的陆地档案，记录了沉积它们的多种冰源。这些变化包括东北流冰覆盖了横贯南极山脉，东南极冰盖向东扩张，罗斯冰架向西延伸代表了西南极冰盖的扩张，以及当地高山冰川的增长。南极洲的冰碛物和冰碛物通常以斑块或脱节的露头模式孤立存在，这使得很难将冰碛物联系起来并确定其来源。本项目将对麦克默多干河谷的冰碛物进行系统研究，以利用各种地球化学技术确定其来源，包括用X射线荧光、重矿物成分、土壤盐浓度进行主元素和次元素分析，并确定这些冰碛物中所含锆石砂的铀铅年龄。主要的工具将是冰川漂移中碎屑锆石人口的年龄分布，因为它反映了冰碛物的来源，并提供了一个独特的地球化学“指纹”，用于区分源区，同时将不同地点的单元相关联。该项目的一项成果是，为极地岩石储存库中存档的样品绘制的冰川冰碛物的锆石指纹库，以及MDV中系统收集的样品。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。