Collaborative Research: East Antarctic Glacial Landscape Evolution (EAGLE): A Study using Combined Thermochronology, Geochronology and Provenance Analysis

南极洲几乎完全被冰覆盖，有些地方的冰厚超过两英里。这些冰层隐藏着比火星表面更不为人所知的景观，代表着地球上最后的未探索的前沿之一。透冰雷达图像可以远程一睹这一景观，包括比欧洲阿尔卑斯山还大的冰埋山脉和深达大峡谷两倍的巨大峡湾。 该项目的目标是收集来自这些景观的沉积物样本，以确定这些特征的形成时间和条件。 具体来说，该项目旨在了解上覆冰盖的历史和动态以及过去造山事件的背景下的景观。 该项目通过分析之前在南极洲海岸海底钻探探险期间收集的沙子来实现这一目标。这些沙子是由大陆内部 3400 万年前无冰时期的古老河流提供的，后来又由冰川提供的。该项目还将研究横贯南极山脉稀有无冰地区的基岩样本。主要活动是将多种先进的年代测定技术应用于沙子和岩石中包含的单一矿物颗粒。不同的方法和矿物会产生不同的日期，从而可以深入了解南极洲的地貌在沙子沉积在近海的数千万年中是如何被侵蚀的。本研究正在开发和增强的测年技术在地球科学研究和工业的许多分支中具有广泛的应用。 该项目以具有成本效益的方式利用美国国家科学基金会设施中现有的样本收藏，包括美国极地岩石储存库、墨西哥湾沿岸核心储存库和南极海洋地质研究设施。该项目将为两名研究生和两名本科生的 STEM 培训做出贡献，其中包括四所美国大学之间的合作以及美国和法国之间的国际合作。该项目还以为期两周的开放研讨会的形式支持外展活动，让 10 名学生有机会访问亚利桑那大学，进行基于 STEM 的分析工作和南极项目的培训。该项目和研讨会的结果将通过专业会议上的演讲、同行评审的出版物以及公共宣传和媒体进行传播。该项目的主要目标是重建东南极冰下景观演化的年表，以了解景观改变背后的构造和气候强迫，以及它如何影响过去冰盖的形成和动态。我们的方法侧重于获取南极冰川开始之前和之后沉积的近海沉积物中源自东南极的碎屑矿物颗粒和碎屑中所包含的冷却和侵蚀历史记录。样品将从威尔克斯陆地（100°E-160°E）近海和罗斯海的现有钻芯和海洋沉积物芯材料中采集。将采用多种地质和热天文计来重建源区冷却历史，包括锆石和磷灰石的 U-Pb、裂变径迹和 (U-Th)/He 定年法，以及角闪石、云母和长石的 40Ar/39Ar 定年法。该海上记录将通过对从美国极地岩石储存库获得的横贯南极山脉的陆上基岩样本应用相同的方法并通过实地考察进行增强和测试。陆上工作还将解决有争议的切割范围的大型冰川槽的切割历史，这些冰川槽现在被排干南极东部冰盖的冰川所占据。这包括从多个年龄-海拔横断面收集样本、磷灰石 4He/3He 测温法和 Pecube 热运动学建模。获取广泛的地质和热年代数据库还将提供有关鲜为人知的冰下东南极冰下地质和构造的宝贵新信息，这对于改善超大陆重建和理解大陆分裂具有重要意义。

Antarctica is almost entirely covered by ice, in places over two miles thick. This ice hides a landscape that is less well known than the surface of Mars and represents one of Earth's last unexplored frontiers. Ice-penetrating radar images provide a remote glimpse of this landscape including ice-buried mountains larger than the European Alps and huge fjords twice as deep as the Grand Canyon. The goal of this project is to collect sediment samples derived from these landscapes to determine when and under what conditions these features formed. Specifically, the project seeks to understand the landscape in the context of the history and dynamics of the overlying ice sheet and past mountain-building episodes. This project accomplishes this goal by analyzing sand collected during previous sea-floor drilling expeditions off the coast of Antarctica. This sand was supplied from the continent interior by ancient rivers when it was ice-free over 34 million year ago, and later by glaciers. The project will also study bedrock samples from rare ice-free parts of the Transantarctic Mountains. The primary activity is to apply multiple advanced dating techniques to single mineral grains contained within this sand and rock. Different methods and minerals yield different dates that provide insight into how Antarctica?s landscape has eroded over the many tens of millions of years during which sand was deposited offshore. The dating techniques that are being developed and enhanced for this study have broad application in many branches of geoscience research and industry. The project makes cost-effective use of pre-existing sample collections housed at NSF facilities including the US Polar Rock Repository, the Gulf Coast Core Repository, and the Antarctic Marine Geology Research Facility. The project will contribute to the STEM training of two graduate and two undergraduate students, and includes collaboration among four US universities as well as international collaboration between the US and France. The project also supports outreach in the form of a two-week open workshop giving ten students the opportunity to visit the University of Arizona to conduct STEM-based analytical work and training on Antarctic-based projects. Results from both the project and workshop will be disseminated through presentations at professional meetings, peer-reviewed publications, and through public outreach and media.The main objective of this project is to reconstruct a chronology of East Antarctic subglacial landscape evolution to understand the tectonic and climatic forcing behind landscape modification, and how it has influenced past ice sheet inception and dynamics. Our approach focuses on acquiring a record of the cooling and erosion history contained in East Antarctic-derived detrital mineral grains and clasts in offshore sediments deposited both before and after the onset of Antarctic glaciation. Samples will be taken from existing drill core and marine sediment core material from offshore Wilkes Land (100°E-160°E) and the Ross Sea. Multiple geo- and thermo-chronometers will be employed to reconstruct source region cooling history including U-Pb, fission-track, and (U-Th)/He dating of zircon and apatite, and 40Ar/39Ar dating of hornblende, mica, and feldspar. This offshore record will be augmented and tested by applying the same methods to onshore bedrock samples in the Transantarctic Mountains obtained from the US Polar Rock Repository and through fieldwork. The onshore work will additionally address the debated incision history of the large glacial troughs that cut the range, now occupied by glaciers draining the East Antarctic Ice Sheet. This includes collection of samples from several age-elevation transects, apatite 4He/3He thermochronometry, and Pecube thermo-kinematic modeling. Acquiring an extensive geo- and thermo-chronologic database will also provide valuable new information on the poorly known ice-hidden geology and tectonics of subglacial East Antarctica that has implications for improving supercontinent reconstructions and understanding continental break-up.