Collaborative Research - Relationship Between Subglacial Geology and Glacial Processes in West Antarctica: Petrological and Geochemical Analyses of Subglacial and Basal Sediments

0087390格鲁诺 该奖项由极地方案办公室南极地质和地球物理方案提供，支持加利福尼亚大学圣克鲁斯分校、德克萨斯大学奥斯汀分校和俄亥俄州州立大学之间的一个合作研究项目，以调查从西南极冰盖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，和新生代冰川的沉积记录，使冰川学家和地质学家特别感兴趣。冰川学家们担心，在不久的将来，WAIS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，并以该地区为现代的主要范例，建立极地海洋沉积体系的模型。南极洲西部的冰下部分已经逃脱了直接的地质调查，所有关于冰下地质的知识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，导致了几个诱人的模型的生成。例如，冰下存在的高量级、短波长的磁异常促使人们提出这样的命题，即冰盖下可能存在大量（100万立方公里）的晚新生代泛滥玄武岩。另一个重要的模型表明，在WAIS内观察到的快速冰流（~100米/年）和缓慢冰运动（~1-10米/年）的模式受到沉积盆地和抗基岩的冰下分布的控制。这些新的基于地球物理学的模型应该用直接观测来检验，因为它们对我们理解西南极构造历史和预测未来WAIS行为的能力非常重要。冰下地质及其与WAIS的相互作用的新的限制将通过以前从七个地方收集的基底和冰下沉积物的岩石学和地球化学分析获得。这项调查将在检验以下三个假设的背景下进行：（A）冰川沉积物样品中基岩碎屑的物源主要来自西南极;（B）西南极冰下沉积物中的一些碎屑和泥质是由冰川的侵蚀作用形成的。（推断）冰下晚新生代泛滥玄武岩，（C）南极西部冰流下的沉积物是由冰前沉积盆地的冰川侵蚀产生的，但沉积物是从缓慢的-WAIS的移动部分是通过抵抗基岩的侵蚀而产生的。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、地球化学和年龄与泥浆地球化学相结合，以及（C）粘土矿物学/共生关系与砂和粉砂颗粒的结构成熟度相结合。这些测试的结果将有助于评估冰下地质可能对WAIS内快速冰流模式具有一阶控制的有趣可能性。新的数据也将有助于确定南极洲西部的冰下部分是否是晚新生代的玄武岩地区。通过结合南极西部研究的冰川学和地质学方面，拟议的合作项目将增加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。

0087390 Grunow This 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.