COSMOGENIC ³HE AND 10BE SURFACE EXPOSURE DATING OF MORAINES AT EL TATIO, CHILE

Paleoclimatic reconstructions of the extension of alpine glaciers during the Last Glacial Maximum in the subtropical Andean Regions, specifically the Chilean Altiplano, are still uncommon. While the Chilean Altiplano has an elevation >4,000 masl, the current annual precipitation is too low to sustain glaciers. However, the occurrence of prominent moraines, indicates the past presence of alpine glaciers. A colder and more humid environment may have been required to accommodate the creation and growth of glaciers. Previous studies in Chile, utilized glacial features south of the El Tatio and within the Chajnantor Plateau to constrain the age of moraine stabilizations of ca. 25-40 ka, 15-17 ka, and 12-14 ka, but these datasets are still limited to produce good chronologies. To advance these previous studies and further constrain the age of moraines and their relation to glacial extent, we collected 18 samples from andesite boulders in ~5-6 moraines in the El Tatio area. A recent study done in dolerites from Antarctica, used ¹⁰Be and ³He exposure dating on pyroxenes showing promising results that can aid in understanding glacial histories. Same methodology, ³He and ¹⁰Be cosmogenic dating, will be applied to pyroxenes from the sampled andesite boulders. Assuming that glaciers were present in the Chilean Altiplano during the Last Glacial Maximum (~24-18 ka), dating the glacial moraines will provide useful information on the timeline of the glaciers, which can further improve the reconstruction of paleoclimate records in the Atacama Desert, as well as the Southern Hemisphere. Additionally, this work will assist with future research on the local effects of glacial accumulation and retreat on the surrounding areas of the El Tatio.