PALEOHYDROLOGY OF THE LAGUNA LEJIA (NORTH CHILEAN ALTIPLANO) AND CLIMATIC IMPLICATIONS FOR LATE-GLACIAL TIMES

Paleoenvironmental and sedimentological data from Laguna Lejia (23-deg rees-30'S, 67-degrees-42'W, 4325 m) in the high Altiplano of the Chile an Atacama desert indicate that climatic conditions during late-glacia l times were significantly wetter than today. A water and energy budge t model was used to simulate climatic scenarios that would have result ed in the observed changes in the water levels, water surfaces, water volumes and salinity during that time interval. Different climatic sce narios for the Laguna Lejia catchment include precipitation increases of over 100% up to 400- > 500 mm/yr (today 200 mm/yr) to account for t he late-glacial lake levels with shorelines 15-25 m higher than at pre sent, and a lake surface of 9-11 km2 compared to the present 2 km2. Du ring the lake maximum about 13,500-11,300 yr B.P. finely laminated sed iments consisting of Mg-calcite, diatoms and sometimes gypsum were dep osited. The paleoenvironmental evidence indicates that (north)easterly wind direction prevailed, and the summer rainfall resulted from a sea sonal poleward shift of the tropical circulation. The lake history of Laguna Lejia is representative for the Altiplano area between 21-degre es and 24-degrees-S.