THE APPLICATION OF IN SITU COSMOGENIC NUCLIDE EXPOSURE DATING (10BE,26AL), TO GLACIAL DEPOSITS OF THE LAST DEGLACIATION IN THE SOUTHERN ANDES OF CHILE

The timing of high frequency - low amplitude climatic variations during the last glacial/interglacial transition is important to our understanding of the nature of interhemispheric leads and lags in global climate signalling. To this end, the measurement of in situ produced cosmogenic nuclides by AMS provides geomorphologists with an indispensable tool for dating the emplacement of glacial landforms, related to the advance and retreat of glaciers in response to climate.

Fuego Patagonia is one of the only large landmasses to extend beyond 55^o south. It has been suggested that glacial dynamics in this region are controlled by the location, moisture content and intensity of the westerlies, which are themselves controlled by global pressure systems. Knowledge of the timing of glaciation therefore indicates both precipitation and temperature regimes at varying latitudes throughout Patagonia. By constructing an accurate chronology, the nature of interhemispheric climate change during the last glacial termination can be elucidated. This is currently a contentious topic, which continues to be widely debated.

This project applies insitu-cosmogenic nuclide exposure dating to a variety of glacial landforms. These landforms are a product of advancing glaciers during the last glacial cycle. Two sites were selected in southernmost South America; Torres del Paine and The Strait of Magellan based on the findings of geomorphological field studies in this region. These previous studies have identified a series of glacial limits. Attempts to produce a reliable radiocarbon chronology for the Paine and Magellan regions have yielded few useful bracketing dates due to the lack of preserved organic material. A preliminary radiocarbon chronology has been developed from this work, which provides an ideal testing ground for cosmogenic dating.