Glacier advances east of the Southern Andes between the Last Glacial Maximum and 5,000 BP compared with lake terraces of the endorrheic Lago Cardiel (49 degrees S, Patagonia, Argentina)

摘要

Glaciers in southern South America advanced three dines during the late-glacial interval (15,000-10,000 BP) as well as during the early Holocene (10,000-5,000 BP). This was documented by terminal moraines of the Pueyrredon lobe, an outlet glacier of the North Patagonian Icefield, the San Martin lobe, an outlet lacier of the South Patagonian Icefield, and by the valley glacier Belgrano of the southern San Lorenzo Mountains (3,707 in a.s.l.). The terminal moraines deposited during the third late-glacial advance (Younger Dryas stade), and the moraines of the first Holocene advance, which culminated at ca. 8,500 BP, lie nearby, indicating, that an abrupt climatic change did not occur at the end of the late-glacial epoch. The melt-water of the Belgrano Glacier largely drained into endorrheic Lago Cardiel (365 km(2), 49 degrees S; 71 degrees 15'W) until the first late-glacial advance. Afterward, its lake level was mainly controlled by the meltwater of small valley glaciers originating from its northwestern catchment with altitudes between 1,500 and 1,977 m a.s.l. Thus, the melting phases after the second late-glacial advance are related to well known ages of the lake terraces. Therefore, the obtained minimum limit dates of these moraines can be completed by absolute ages. The wealth of advances between 11,000 and 5,000 BP verifies that a "Hypsithermal Interval" did not exist in southern South America.