OSL DATING OF SHORELINE DEPOSITS OF LAGUNA CARI-LAUFQUEN GRANDE, ARGENTINA

Laguna Cari-Laufquen Grande is located at 41^o 10’ S and 69^o 25’ W at an elevation of roughly 785 m in Rio Negro Province, south central Argentina. Previous research shows that the lake level rose and fell repeatedly during the late Pleistocene resulting in several ancient shorelines and lake transgressional/regressional sedimentary sequences. The lake level record of Lake Cari-Laufquen Grande is similar to that of other pluvial lakes in the extra-Andean region in general, as well as high-latitude records from the northern hemisphere. The ages of the shorelines are used for comparison to determine whether climate factors such as shifting atmospheric circulation patterns and depressed temperatures could be a common cause for lake expansion in the northern and southern hemispheres during the last glacial maximum (LGM). A set of samples collected from Laguna Cari-Laufquen Grande was dated using optically stimulated luminescence (OSL) in order to determine the age of the most prominent shorelines and to relate them to a deep water phase previously constrained to 27 - 22 ka. Changing atmospheric circulation patterns in the Atlantic domain, and lower temperatures are thought to have caused an increase in precipitation in the region of Cari-Laufquen during the LGM leading to the deep water phase and potentially the creation of the prominent shorelines. OSL dating is a technique that uses dosimetric properties of mineral grains to determine the depositional age of samples. The samples analyzed for this report were very coarse grained and very little quartz in the 90-250 micron fraction, used for the OSL dating, was recovered. Nevertheless dating measurements have been undertaken. This presentation will overview the OSL dating effort and present the preliminary results obtained.