COLLABORATIVE RESEARCH:Relationship Between Subglacial Geology and Glacial Processes in West Antarctica: Petrological and Geochemical Analyses of Subglacial and Basal Sediments

该奖项由极地项目办公室的南极地质和地球物理项目提供，支持加州大学圣克鲁斯分校、德克萨斯大学奥斯汀分校和俄亥俄州立大学之间的合作研究项目，以调查从南极西部冰盖（WAIS）底部回收的沉积物样本。西南极洲是一个遥远的极地地区，但其动态冰盖、复杂的构造历史和新生代冰川沉积记录使其成为冰川学家和地质学家特别感兴趣的地方。冰川学家担心，在不久的将来，西洋带的物质平衡可能会发生重大变化，这可能会导致全球海平面持续上升。地质学家正在南极洲西部调查大陆伸展的基本过程，并以该地区为主要的现代例子，构建极地海洋沉积体系的模型。西南极洲的冰下部分没有直接的地质调查，所有对冰下地质的了解都来自地球物理遥感。最近获得的新的、高质量的地球物理数据产生了几个诱人的模型。例如，冰下存在高强度、短波长的磁异常，这促使人们提出在冰盖下可能存在大量（100万立方千米）晚新生代洪水玄武岩的主张。另一个重要的模式表明，在WAIS内观测到的快速冰流（~100米/年）和缓慢冰运动（~1-10米/年）的模式是由沉积盆地和抵抗基岩的冰下分布控制的。这些基于地球物理学的新模型应该通过直接观测进行检验，因为它们对我们了解南极西部的构造历史和预测西海的未来行为的能力非常重要。这项研究是一项试验性研究，旨在提供新的地质数据，这些数据可能有助于检验最近从地球物理观测中推断出的模型。通过对先前从七个地点收集的基底和冰下沉积物的岩石学和地球化学分析，将获得冰下地质及其与WAIS相互作用的新限制。这项调查将在测试以下三个假设的背景下进行：(A)冰川沉积物样品中的基岩碎屑主要来自南极西部，(B)南极西部冰下沉积物中的一些碎屑和泥是由（推断的）晚新生代冰下洪水玄武岩的侵蚀作用产生的。(C)南极西部冰流下的沉积物是由冰期前沉积盆地的冰川侵蚀产生的，而从WAIS缓慢移动部分下方回收的沉积物是由抗性基岩侵蚀产生的。将通过收集以下数据来检验各个假设：(A)花岗岩类碎屑的岩石学、地球化学和年龄；(B)玄武岩碎屑的岩石学、地球化学和年龄结合泥浆地球化学；(C)粘土矿物学/共生结合砂粒和粉粒的结构成熟度。这些试验的结果将有助于评估一种有趣的可能性，即冰下地质可能对西沙区内快速冰流的模式具有一级控制。新的数据也将有助于确定西南极洲的冰下部分是否是一个晚新生代洪水玄武岩省。通过结合南极西部冰川学和地质学方面的研究，拟议的合作项目将有助于美国正在进行的努力，以建立对这一极地地区的多学科理解。

0087393SternThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research project between the University of California-Santa Cruz, the University of Texas-Austin, and the Ohio State University to investigate sediment samples recovered from the base of the West Antarctic Ice Sheet (WAIS). West Antarctica is a remote polar region but its dynamic ice sheet, complicated tectonic history, and the sedimentary record of Cenozoic glaciation make it of particular interest to glaciologists and geologists. Glaciologists are concerned with the possibility of significant near-future changes in mass balance of the WAIS that may contribute to the ongoing global sea level rise. Geologists are investigating in West Antarctica the fundamental process of continental extension and are constructing models of a polar marine depositional system using this region as the prime modern example. The subglacial part of West Antarctica has escaped direct geological investigations and all that is known about subglacial geology comes from geophysical remote sensing. Recent acquisitions of new, high-quality geophysical data have led to generation of several enticing models. For instance, subglacial presence of high-magnitude, short-wavelength magnetic anomalies has prompted the proposition that there may be voluminous (1 million cubic km), Late Cenozoic flood basalts beneath the ice sheet. Another important model suggests that the patterns of fast ice streaming (~100 meters/year) and slow ice motion (~1-10 meters/year) observed within the WAIS are controlled by subglacial distribution of sedimentary basins and resistant bedrock. These new geophysics-based models should be tested with direct observations because they are of such great importance to our understanding of the West Antarctic tectonic history and to our ability to predict the future behavior of the WAIS.This research is designed as a pilot study to provide new geologic data, which may help to test the recent models inferred from geophysical observations. The new constraints on subglacial geology and on its interactions with the WAIS will be obtained through petrological and geochemical analyses of basal and subglacial sediments collected previously from seven localities. This investigation will take place in the context of testing the following three hypotheses: (A) the provenance of bedrock clasts in the glacial sediment samples is primarily from West Antarctica, (B) some clasts and muds from the West Antarctic subglacial sediments have been derived by erosion of the (inferred) subglacial Late Cenozoic flood basalts, and (C) the sediments underlying the West Antarctic ice streams were generated by glacial erosion of preglacial sedimentary basins but the sediments recovered from beneath the slow-moving parts of the WAIS were produced through erosion of resistant bedrock.The individual hypotheses will be tested by collecting data on: (A) petrology, geochemistry and age of granitoid clasts, (B) petrology, geochemistry and age of basaltic clasts combined with mud geochemistry, and (C) clay mineralogy/paragenesis combined with textural maturity of sand and silt grains. The results of these tests will help evaluate the interesting possibility that subglacial geology may have first-order control on the patterns of fast ice flow within the WAIS. The new data will also help to determine whether the subglacial portion of West Antarctica is a Late Cenozoic flood basalt province. By combining glaciological and geological aspects of West Antarctic research the proposed collaborative project will add to the ongoing U.S. effort to create a multidisciplinary understanding of this polar region.