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的淡水。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，例如通过大型冰坝湖泊排水事件。大量冰川融水的快速释放是非常重要的，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。在冰盖生长、末次盛冰期和消冰期的不同时期，在巴塔哥尼亚冰盖的东侧翼形成了大型冰川湖。随着冰盖形状和大小的改变，融化的水周期性地从巴塔哥尼亚冰盖周围的湖泊排放到南太平洋，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这些大型冰川湖的轮廓和演变，这些冰川湖形成于智利和阿根廷巴塔哥尼亚冰盖以东，在最后一次冰川极大期的衰退时期。通过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的范围及其主要融水排水路线（例如，前三角洲、海岸线、溢洪道和排水渠道）。该提案寻求资金（实地考察旅费和生活费用、技术支持和实验室分析费用），以使用一种称为单粒光激发光（OSL）的测年技术，从前冰湖边缘收集冰湖沉积物样本并确定其日期。我们进行了一项概念验证研究，使用了2006年从前冰川湖沿岸收集的两个样本。这些样品表明，OSL定年法在次千年时间尺度上为冰湖沉积物定年提供了一种很好的方法。获得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时期的时间，因为冰川前进时湖泊会充满（阻塞湖泊），冰川后退时湖泊会清空（允许湖泊自由排水）。因此，将地貌学与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。这是很重要的，因为这种消冰的性质和时间是有争议的，因为它与北半球的消冰事件的同步性（或其他）是有争议的。通过确定湖泊排水事件的年代，我们还将能够计算出每次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.