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

ANDRZEJ TATUR; RODOLFO DEL VALLE; MARIA-MARTHA BIANCHI; VALERIA OUTES; GUSTAVO VILLAROSA; JERZY NIEGODZISZ

QUATERNARY INTERNATIONAL

Elsevier

Lugar: Amsterdam; Año: 2002 vol. 89 p. 135 - 150

1040-6182

Late Pleistocene palaeolakes on the eastern side of Andes (glacial lakes) and in the Patagonian Steppe (pluvial lakes) along 411S latitude were studied. Natural dams (glaciers, moraines) that maintained a high water level in glacial palaeolakes were melted or cut by erosion during Late Pleistocene climate amelioration. With the retreat of the glaciers from the Andean valleys during prominent regional deglaciation, outflow from the eastern side of Andes to the Pacific Ocean was formed about 13.2 ka BP. As a result, the water level in glacial palaeolakes fell rapidly in stages. These changes were often preceded by volcanic-tectonic activity, which is suggested to be the ‘‘touch of butterfly’’ releasing mass balance adjustment in the 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 deglaciation 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 surrounding mountains and elevated plains. r 2002 Elsevier Science Ltd and INQUA. All rights reserved.