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，有些地方超过两英里厚。这块冰隐藏着一片不像火星表面那么广为人知的景观，代表着地球上最后几个未被探索的边界之一。穿透冰层的雷达图像提供了这一景观的远程一瞥，包括比欧洲阿尔卑斯山更大的冰盖山脉和比大峡谷深两倍的巨大峡湾。该项目的目标是收集来自这些景观的沉积物样本，以确定这些特征形成的时间和条件。具体地说，该项目试图在覆盖的冰盖和过去的造山事件的历史和动态的背景下了解这一景观。该项目通过分析以前在南极洲海岸进行海底钻探探险时收集的沙子来实现这一目标。这些沙子在3400万年前没有冰的时候是由古老的河流从大陆内陆提供的，后来又由冰川提供。该项目还将研究横贯北极山脉罕见的无冰地区的基岩样本。主要的活动是将多种先进的测年技术应用于这些沙子和岩石中包含的单一矿物颗粒。不同的方法和矿物产生不同的日期，让我们深入了解南极洲S的景观是如何在几千万年的时间里被侵蚀的，在此期间，沙子被沉积在近海。正在为这项研究开发和改进的测年技术在地学研究和工业的许多分支中都有广泛的应用。该项目经济高效地利用了美国国家科学基金会设施中已有的样本收集，这些设施包括美国极地岩石库、墨西哥湾沿岸岩心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，包括美国四所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讲习班的形式支持外联活动，使十名学生有机会访问亚利桑那大学，就南极项目开展基于STEM的分析工作和培训。该项目和讲习班的成果将通过在专业会议上的发言、同行评议的出版物以及通过公众宣传和媒体传播。该项目的主要目标是重建东南极冰下地貌演变的年表，以了解地貌变化背后的构造和气候驱动力，以及它如何影响过去的冰盖开始和动态。我们的方法侧重于获取南极东部衍生的碎屑矿物颗粒和南极冰川开始之前和之后沉积的近海沉积物中的碎屑中包含的冷却和侵蚀历史的记录。样品将从威尔克斯近海(100°E-160°E)和罗斯海现有的钻探岩心和海洋沉积物岩心材料中提取。将利用多种地质和热年代学方法重建源区冷却历史，包括锆石和磷灰石的U-Pb、裂变径迹和(U-Th)/He年龄，以及角闪石、云母和长石的40Ar/39Ar年龄。这一近海记录将通过将同样的方法应用于从美国极地岩石储存库获得的横跨北极山脉的陆上基岩样本并通过实地工作来扩大和测试。陆上的工作还将解决有争议的大型冰槽切割历史，这些冰槽切断了山脉，现在被排干东南极冰盖的冰川占据。这包括从几个年龄标高断面收集样本，磷灰石4He/3He热计时，以及Pecube热运动学模拟。获取一个广泛的地理和热年代学数据库还将提供有关东南极冰下鲜为人知的冰层隐藏地质和构造的宝贵新信息，这对改进超大陆重建和了解大陆解体具有重要意义。

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.