Late-glacial history of Lago Argentino, Argentina, and age of the Puerto Bandera moraines

In the west-central part of Lago Argentino, the Puerto Bandera moraines are clearly detached from longer, more prominent moraines of the last glaciation and from shorter and smaller Neoglacial moraines, Scientists have long speculated about the age of the Puerto Bandera moraines, Detailed geomorphologic studies in the western area of Lago Argentino, including stratigraphic profiles at Bahia del Quemado in the northern branch (Brazo Norte), indicate that the Puerto Bandera moraines were deposited by three pulses of ice. Each of the three pulses is represented by single moraine ridges and belts of tightly arranged ridges. The timing of the three glacier advances was established by radiocarbon dating, including data published by John Mercer. The oldest moraine system, formed during the Puerto Bandera I substade, was deposited ca. 13,000 C-14 yr B.P. Moraines of the Puerto Bandera II substade were deposited ca, 11,000 C-14 yr B.P. The youngest moraine system was deposited during a minor readvance, shortly before 10,390 C-14 yr B.P., and thus appears to have occurred some time during the European Younger Dryas interval. After this third substade, the ice tongues retreated into the interior branches of Lago Argentino and have remained there since. Evidence found at Bahia del Quemado, together with data provided by other authors, attests to a significant climatic change by the middle Holocene, which we believe occurred during the Herminita advance, the first Holocene glacial readvance recognized within the area. (C) 2000 University of Washington.