Collaborative Research: The NE Sector of the Laurentide Ice Sheet: Dating Outlet and Local Glacier Moraines at Clyde with Cosmogenic Isotopes

摘要米勒OPP-0004466这是一项与佛蒙特州大学、科罗拉多州大学以及本特利学院合作的提案。我们对劳伦蒂德冰盖的看法已经从一个具有相对稳定的中央核心的厚重的整体圆顶变成了一个更薄、更多圆顶和更动态的冰系，具有内在的不稳定性。冰盖在气候系统中的作用包括随着高度的增加对大气流动的扰动，以及由于反照率的变化而改变行星能量平衡。此外，通过大量的冰山和融水排放，冰盖是北大西洋热盐环流的决定因素。有关大陆冰川形成的时间和类型的主要信息在这一概念演变中发挥了关键作用。沿着劳伦蒂德冰盖的东北边缘，广泛的冰川系列提供了过去冰盖行为的直接记录。早期的研究因无法直接确定这些存款的年代而受到限制。因此，提出了沿冰盖所有边缘的冰川推进的时间和大小相似的论点，以及前冰盖不同部分之间基本上不同步的反应。随着宇宙暴露测年技术的发展，现在可以直接测定冰雹的年龄，并解决这一争论的大部分问题。首席调查人员最近的研究通过确定巴芬岛南部冰川特征的年代确定了该方法的实用性，并证明该地区在最后一次冰川高峰期完全冰化。然而，他们也有证据表明，东北海岸的冰川强度较小，保存的冰川历史要长得多。首席调查员将在东北劳伦蒂德冰盖的典型所在地克莱德地区进行为期一年的研究。在米勒和戴维斯丰富的巴芬岛实地经验以及比尔曼和施泰格的宇宙学专业知识的基础上，他们将绘制冰川沉积、冰流特征和冰川地貌的系统变化图，并收集用于宇宙成因和放射性碳测年的样本。他们的结果将确定宇宙成因暴露测年在该地区的适宜性，最佳样本类型，并解决第一级问题：最后一次冰川最大年龄的前海地区是否保存了大片冰川，或者它们是否代表了更古老的冰川？宇宙学和放射性碳数据与实地冰川沉积和航空照片的直接测绘相联系，将使它们能够更好地确定冰川作用的样式和时间，以及冰川周期初始阶段的性质。

AbstractMillerOPP- 0004466This is a collaborative proposal with the Universities of Vermont and Colorado and Bentley College. Our view of the Laurentide Ice Sheet has changed from a thick monolithic dome with a relatively stable central core to a thinner, multi-domed and more dynamic ice system with inherent instabilities. The role of the ice sheet in the climate system includes perturbations to atmospheric flow as its height increased, and altering the planetary energy balance due to albedo changes. In addition, through massive ice-berg and meltwater discharges, the ice sheet was a determinant on North Atlantic thermo-haline circulation.Primary information on the timing and style of continental glaciation has played a key role in this conceptual evolution. Along the northeastern margin of the Laurentide Ice Sheet, extensive series of moraines provide a direct record of past ice-sheet behavior. Early studies were limited by an inability to date these deposits directly. Consequently, arguments were advanced for both a similar timing and magnitude of glacial advances along all margins of the ice sheet, and for fundamentally asynchronous responses between different sectors of the former ice sheet. With the development of cosmogenic exposure dating, it is now possible to date the moraines directly and resolve much of this debate. Recent studies by the Principal Investigators have established the utility of the method by dating glacial features on southern Baffin Island and demonstrated that this region was completely glaciated at the last glacial maximum. However, they also have evidence that the northeastern coast was less intensively glaciated and preserves a much longer glacial history.The Principal Investigators will conduct a one-year study in the Clyde region which is the type site for the NE Laurentide Ice Sheet. Building on the extensive Baffin Island field experience of Miller and Davis, and the cosmogenic expertise of Bierman and Steig, they will map glacial deposits, ice-flow characteristics, and systematic changes in the glacial geomorphology, and collect samples for cosmogenic and radiocarbon dating. Their results will establish the suitability of cosmogenic exposure dating in this region, the optimum sample type, and address the first-order question: are the extensive moraines preserved on the forelands of last glacial maximum age or do they represent much older glaciations? The cosmogenic and radiocarbon data, linked to direct mapping of glacial deposits in the field and on aerial photographs, will allow them to better define the style and timing of glaciation, and the nature of the inception phase of a glacial cycle.