Collaborative Research: EAGER: Development of a Method for Paired Potassium/Argon Geochronology and Strontium-Neodymium-Lead Radiogenic Isotope Geochemistry of Dust in Ice Cores

合作研究：EAGER：开发冰芯尘埃配对钾/氩地质年代学和锶-钕-铅放射性同位素地球化学方法

• 批准号: 2032849
• 负责人: Sidney Hemming
• 金额: $ 8.27万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2032849&HistoricalAwards=false
• 关键词: Collaborative; Research; EAGER; Development; Method

Atmospheric dust and sediment serve as valuable tracers of past Earth and ocean processes because their geochemical compositions reflect their bedrock parent material. Scientists use the compositions of sediments and dust as a ‘fingerprint’, linking materials at downstream sites, such as ice and sediment cores, back to their sources. Through geochemical fingerprinting, scientists have gained insight into the causes and impacts of abrupt climate changes, the stability of ice sheets and their potential contributions to sea level rise, and the mechanisms by which ocean and atmospheric circulation patterns change. This project aims to harness the capabilities of two different techniques used to determine sediment provenance. The approach will allow the team to address critical questions regarding past wind patterns around Antarctica, the roles of different dust sources in supplying nutrients to the Southern Ocean, and the behavior of the West Antarctic Ice Sheet during the last interglacial warm period. In addition, the method has the potential to be applied to extraterrestrial materials such as from the Mars Mission and Moon rocks. Geochemical tracing of dust and other sediment sources is a powerful approach that aids in reconstructing past atmosphere, ocean, and ice-sheet dynamics. However, in some regions such as the Southern Hemisphere, even multi-variate approaches such as those using strontium, neodymium, and lead isotopes yield ambiguous results due to overlapping source-area compositions. The team has found that lead isotopes add great value in distinguishing sources and that combining these with potassium/argon geochronology provides significant additional constraints on sediment provenance. The added value is due to the relative ease of resetting potassium/argon ages during subsequent geologic events such as crystallization of new minerals during diagenesis, or by heating, with resetting occurring at lower temperatures than other isotopic systems. The team will develop and test the proposed approach using rock and mineral standards and fine-grained sediments, then apply it to ice-core dust samples from deaccessioned ice cores and dust from the Last Glacial Maximum at key sites. Beyond the broader scientific impact of this new approach, the project will provide opportunities for Colby College undergraduates to experience complete immersion in the world of discovery, working both in Dr. Bess Koffman’s geochemistry lab at Colby and at the Lamont-Doherty Earth Observatory of Columbia University, where they will engage with a wider cohort of students from around the country and have access to state-of-the-art analytical facilities.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.

大气尘埃和沉积物是过去地球和海洋过程的宝贵示踪剂，因为它们的地球化学成分反映了它们的基岩母物质。科学家们将沉积物和灰尘的成分作为“指纹”，将下游地点的物质（如冰和沉积物岩心）与它们的来源联系起来。通过地球化学指纹图谱，科学家们已经深入了解了气候突变的原因和影响，冰盖的稳定性及其对海平面上升的潜在贡献，以及海洋和大气环流模式变化的机制。该项目旨在利用两种不同的技术来确定沉积物的来源。这种方法将使研究小组能够解决一些关键问题，如南极洲周围过去的风模式，不同的尘埃来源在向南大洋提供营养物质方面的作用，以及南极西部冰盖在最后一次间冰期温暖期的行为。此外，该方法有可能应用于火星任务和月球岩石等地外物质。地球化学示踪的灰尘和其他沉积物来源是一个强大的方法，有助于重建过去的大气，海洋和冰盖的动态。然而，在南半球等一些地区，即使是使用锶、钕和铅同位素等多变量方法，由于源区成分重叠，结果也不明确。研究小组发现，铅同位素在区分沉积物来源方面有很大的价值，将这些同位素与钾/氩地质年代学相结合，可以对沉积物的来源提供重要的额外限制。增加的价值是由于在随后的地质事件中相对容易重置钾/氩年龄，例如在成岩作用期间新矿物的结晶，或者通过加热，重置发生在比其他同位素系统更低的温度下。该团队将使用岩石和矿物标准以及细粒度沉积物开发和测试所提出的方法，然后将其应用于关键地点的脱氮冰芯和末次冰期极大期的冰芯尘埃样本。除了这种新方法的更广泛的科学影响之外，该项目还将为科尔比学院的本科生提供机会，让他们在科尔比的贝斯·科夫曼博士的地球化学实验室和哥伦比亚大学的拉蒙特-多尔蒂地球天文台工作，体验完全沉浸在发现的世界中，在那里他们将与来自全国各地的更广泛的学生接触，并有机会使用最先进的分析设施。该奖项反映了美国国家科学基金会的法定使命，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。