Collaborative Research: Pleistocene East Antarctic Ice Sheet History as Recorded in Sediment Provenance and Chronology of High-elevation TAM Moraines

本研究将研究横跨横跨横贯南极山脉（TAM）的两个同心序列的更新世冰碛物的冰碛物成分随时间的变化。这项工作的年代学框架将由突出的山脊上的巨石的宇宙暴露年龄产生。pi假设，冰碛物成分的变化可能表明冰流方向的变化或原始源区成分的变化，而冰碛物的年龄提供了长期陆地冰盖动力学的视角。这两个结果对于旨在重建南极东部冰盖和评估其在全球气候系统中的作用及其对全球海平面上升的潜在影响的模拟实验至关重要。随着时间的推移，土壤成分的变化也使得对罗斯海和南大洋沉积物岩心的解释更加准确。此外，一些东南极洲出口冰川顶部的暴露物已被证明含有来自东南极洲基岩的冰下物质，这为透过冰层观察东南极洲提供了一个窗口。难以接近的基岩。Till样本将从两个保存完好的冰碛峰顶序列中收集，分别位于Howe山（Scott冰川的头部）和Achernar山（Beardmore和Nimrod冰川之间）。冰碛物中的每一种粒度都提供了潜在的有价值的信息，pi将测量碎屑和砂组分的岩石学，破碎2mm组分的定量x射线衍射，粉砂/粘土组分的元素丰度，以及砂组分中碎屑锆石的U/Pb。数据收集将依赖于以前在该地区使用的既定方法，并且pi还将探索评估其有效性的新方法。在相同的冰碛垄上取样进行物源研究，PIs将取样进行宇宙形成表面暴露分析，以提供一个时间框架，在这些地点进行物源随时间的变化。更广泛的影响拟议的研究涉及研究生和本科生在实验室方法多样化的训练。学生和pi将向社区和校园团体进行演讲，并接受当地新闻媒体的采访。拟议的工作还在IUPUI和LDEO的科学家之间建立了一种新的、潜在的长期合作，并为南极地球科学领域带来了一位新的PI （Kaplan）。

Intellectual Merit The proposed work will investigate changes in the compositional variation of glacial tills over time across two concentric sequences of Pleistocene moraines located adjacent to the heads of East Antarctic outlet glaciers in the Transantarctic Mountains (TAM). The chronologic framework for this work will be generated from cosmogenic exposure ages of boulders on prominent morainal ridges. The PIs hypothesize that variations in till composition may indicate a change in ice flow direction or a change in the composition of the original source area, while ages of the moraines provide a long-term terrestrial perspective on ice sheet dynamics. Both results are vital for modeling experiments that aim to reconstruct the East Antarctic Ice Sheet and assess its role in the global climate system and its potential impact on global sea level rise. The variation of till compositions through time also allows for a more accurate interpretation of sediment cores from the Ross Sea and the Southern Ocean. Additionally, till exposures at the head of some East Antarctic outlet glaciers have been shown to contain subglacial material derived from East Antarctic bedrock, providing a window through the ice to view East Antarctica?s inaccessible bedrock. Till samples will be collected from two well-preserved sequences of moraine crests at Mt. Howe (head of Scott Glacier) and Mt. Achernar (between Beardmore and Nimrod Glaciers). Each size fraction in glacial till provides potentially valuable information, and the PIs will measure the petrography of the clast and sand fractions, quantitative X-ray diffraction on the crushed 2mm fraction, elemental abundance of the silt/clay fraction, and U/Pb of detrital zircons in the sand fraction. Data collection will rely on established methods previously used in this region and the PIs will also explore new methods to assess their efficacy. On the same moraines crests sampled for provenance studies, the PIs will sample for cosmogenic surface exposure analyses to provide a chronologic framework at the sites for provenance changes through time. Broader Impact The proposed research involves graduate and undergraduate training in a diverse array of laboratory methods. Students and PIs will be make presentations to community and campus groups, as well as conduct interviews with local news outlets. The proposed work also establishes a new, potentially long-term, collaboration between scientists at IUPUI and LDEO and brings a new PI (Kaplan) into the field of Antarctic Earth Sciences.