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

学术价值拟议的工作将研究位于横贯南极山脉（TAM）的东南极出口冰川头部附近的更新世冰碛的两个同心序列中冰川碛物成分随时间变化的变化。这项工作的年代框架将根据突出的冰碛山脊上巨石的宇宙成因暴露年龄生成。 PI 假设，冰碛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，而冰碛的年龄提供了冰盖动力学的长期陆地视角。这两项结果对于旨在重建东南极冰盖并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。蒂尔成分随时间的变化也使得能够更准确地解释罗斯海和南大洋的沉积岩芯。此外，事实证明，一些东南极洲出口冰川顶部的裸露物含有来自东南极洲基岩的冰下物质，为观察南极洲东部难以接近的基岩提供了一个透过冰层的窗口。样品将从豪山（斯科特冰川顶端）和阿彻纳山（比尔德莫尔冰川和尼姆罗德冰川之间）两个保存完好的冰碛嵴序列中采集。冰碛物中的每个尺寸部分都提供了潜在的有价值的信息，PI 将测量碎屑和砂部分的岩相学、破碎的 2mm 部分的定量 X 射线衍射、粉砂/粘土部分的元素丰度以及砂部分中碎屑锆石的 U/Pb。数据收集将依赖于该地区先前使用的既定方法，PI 还将探索新方法来评估其功效。在为起源研究采样的同一冰碛顶部，PI 将采样进行宇宙成因表面暴露分析，以便为不同时间的起源变化提供一个年代框架。更广泛的影响拟议的研究涉及对研究生和本科生进行各种实验室方法的培训。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、可能长期的合作，并将新的 PI (Kaplan) 引入南极地球科学领域。

Intellectual MeritThe 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 ImpactThe 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.