Optically Stimulated Luminescence (OSL) dating of glacial lake drainage during the deglaciation of the Patagonian Ice Sheet

当冰川和冰盖融化时，它们会向海洋释放大量淡水。有时这种释放是渐进的，例如通过河流，有时这种释放是灾难性的，例如通过大型冰堰湖排水事件。大量冰川融化水的迅速释放非常重要，因为最近的研究强调了它们在影响深海环流从而影响气候方面的作用。在巴塔哥尼亚冰盖东侧，在冰盖生长、末次冰盛期和消融期间的不同时期形成了大型冰川湖泊。随着冰盖的形状和大小发生变化，融化的水定期从巴塔哥尼亚冰盖周围的湖泊流入南太平洋，但我们不知道这些排水事件的确切时间。该项目的目的是重建智利和阿根廷巴塔哥尼亚冰盖以东的这些大型冰川湖泊的轮廓和演化，这些湖泊在从最后一次冰川最大位置开始衰退期间形成。利用卫星遥感图像和实地调查，我们知道我们可以确定这些前冰川湖泊的范围和它们的主要融水排水路线(例如，以前的三角洲、海岸线、溢洪道和排水渠道)。这项提议寻求资金(实地考察、旅行和生活费、技术支持和实验室分析费用)，以便使用一种名为单颗粒光激发发光(OSL)的测年技术，从前冰川湖泊边缘收集冰川湖泊沉积物样本并测定其年代。我们进行了一项概念验证研究，使用了我们在2006年从前冰川湖泊海岸周围收集的两个样本。这些样本表明，OSL测年提供了一种极好的方法，可以在亚千年的时间尺度上测定冰川湖泊沉积物的年龄。获取湖泊生长和排水的日期将使我们能够确定冰川扩张和收缩的时间，因为湖泊在冰川前进时充满(筑坝)，而湖泊在冰川消退时排空(允许湖泊自由排水)。因此，将地貌学和OSL测年相结合，提供了一种重建该地区巴塔哥尼亚冰盖退缩的新方法。这一点很重要，因为冰川消融的性质和时间是有争议的，而且它与北半球冰川消融事件的同时性(或其他)也存在争议。通过对湖泊排水事件的测年，我们还能够计算出每个主要排水事件期间的融水体积和通量。

When glaciers and ice sheets melt, they release large volumes of fresh water into the oceans. Sometimes this release is gradual, for example via rivers, and sometimes this release is catastrophic, for example via large ice-dammed lake drainage events. The rapid release of large quantities of glacial meltwater are very important because recent research has highlighted their role in influencing deep sea circulation and therefore climate. Large glacial lakes formed on the eastern flank of the Patagonian Ice Sheet at various times during ice sheet growth, at the Last Glacial Maximum and during deglaciation. The meltwater periodically discharged from the lakes surrounding the Patagonian Ice Sheet into the Southern Pacific as the ice sheet changed shape and size, but we do not know the precise timing of these drainage events. The aim of this project is to reconstruct the outline and evolution of these large glacial lakes that formed east of the Patagonian Ice Sheet in Chile and Argentina during recession from its Last Glacial Maximum position. Using satellite remote-sensing images and fieldwork surveys we know that we can identify the extent of these former glacial lakes and their principal meltwater drainage routes (e.g. former deltas, shorelines, spillways and drainage channels). This proposal seeks funds (fieldwork travel and subsistence costs, technical support and laboratory analytical expenses) to collect and date samples of glacial lake sediments from around the margins of the former glacial lakes using a dating technique known as single grain Optically Stimulated Luminescence (OSL). We have conducted a proof-of-concept study using two samples that we collected in 2006 from around the shores of the former glacial lakes. These samples indicate that OSL dating provides an excellent means of dating glacial lake sediments on sub-millenial timescales. Obtaining dates for the growth and drainage of the lakes will enable us to determine the timing of periods of glacier expansion and contraction because the lake filled at times when glaciers advanced (damming the lake) and the lake emptied when glaciers receded (allowing the lake to drain freely). Combining geomorphology with OSL dating therefore provides a novel method of reconstructing the recession of the Patagonian Ice Sheet in this area. This is important because the nature and timing of this deglaciation is controversial and because its synchoneity (or otherwise) with deglacial events in the Northern Hemisphere is debated. By dating the lake drainage events we will also be able to calculate the meltwater volumes and fluxes during each of the major drainage events.