Late Pleistocene paleolakes in Andean and Extra-Andean Patagonia at mid-latitudes of South America

Late Pleistocene paleolakes on the eastern side of Andes (glacial
lakes) and in the Patagonian Steppe (pluvial lakes)along 41?S latitude
were studied. Natural Dams (glaciers, moraines) that maintained a high
water level in glacial paleolakes were melted or cut by erosion during
Late Pleistocene climate amelioration. With the retreat of the glacier
from the Andean valleys during prominent regional deglaciation, water
levels in glacial paleolakes fell rapidly in stages due to the
outflow from the eastern side of Andes to the Pacific Ocean at
about 13.2 ka BP. These changes were often preceded by
volcanic-tectonic activity, which is suggested to be the "touch of
butterfly" releasing mass balance adjustment in changing
landscape. The lacustrine tephra stratigraphic pattern from the Andes,
comprising more than 50 horizons since the last glaciation, is
presented. The correlation of palaeoenvironmental changes between the
Andes and the Patagonian Steppe is suggested on the basis of two
dacite marker horizons. The glaciation event that led to development
of the new hydrological system in the Andean palaeolakeland formed
several large but short-lived palaeolakes in closed basins in the
Patagonian Steppe probably due to melting of local ice and permafrost
accumulated during glaciation on the sourrounding mountains and
elevated plains.