SEDIMENTARY AND MINERALOGICAL INDICATORS OF LATE HOLOCENE PALEOCLIMATE IN SOUTHERN PATAGONIA FROM LAGUNA AMARGA

Laguna Amarga (51° 00' S, 72° 45' W), a small, shallow (~2 m max. depth), low elevation (~148 m.a.s.l) lake, is located just outside of the spectacular Torres del Paine National Park in Chilean Patagonia. This lake is unique for the area in that it is a closed basin lake shut off by ridges and glacial moraines. The lake is supersaturated with respect to gypsum and is bordered by fossilized algal bioherms and interesting mineral springs near its shore. Since Laguna Amarga is not connected to an outside water source, it is very responsive to changes in the regional moisture balance and we expect that its sediment record accurately reflects past conditions in the region where few paleoclimate records have been collected and published. During January of 2005 we recovered two nearly identical one meter-long sediment cores from Laguna Amarga, using a Livingstone corer. Here, we present preliminary results of our sedimentary and mineralogical analysis of the cores to provide insight into the climatic and environmental changes taking place during the late Holocene in the Torres del Paine region. Initial observations of the two cores reveal an intriguing sedimentary history within the lake basin. The sediments in the lake exhibit millimeter- to centimeter-thick laminations which hold a detailed record of local and regional change. Significant changes in the composition of the sediments suggest sharp fluctuations in the lake water balance which is strongly linked to the intensity of the westerly winds providing moisture to the region.