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

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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.