A New Pleistocene Glacial Chronology from Patagonia

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Glacial deposits formed during past expansions of the Patagonian ice fields provide a continuous record of southern hemisphere glaciation and climate change. A precise chronology of these mid-latitude glacial advances is necessary to determine if climate changes were simultaneous in the northern and southern hemispheres, which is a key factor in understanding the triggering mechanism(s) for the ice ages. The common assumption, that glacial advances in the Andes were synchronous with North American glaciations, is based on limited chronological information. This award supports a study to obtain a new high precision chronology of glacial moraines at Lago Buenos Aires, which record Quaternary fluctuations in the Patagonian ice fields. The moraines are extremely well-preserved and have excellent bracketing chronology, due to coexisting Ar-dated lava flows, but there is no direct chronology. This study will obtain surface exposure dates, using 3He, 21Ne, 10Be and 36Cl on boulder samples from the distinct moraine ridges. This research will combine field efforts for sample collection and a laboratory effort to determine the ages of the moraines.