Late-glacial fluctuations of South Patagonian Icefield, Torres del Paine National Park, southern Chile

Abstract

Evidence of two Late-glacial advances of the South Patagonian Icefield at Torres del Paine (51°S, 73°W), Chile, challenges the view that climate in southernmost South America was characterised by uninterrupted warming after Termination 1. The advances are identified by ice marginal deposits, including well-defined end moraines, 18–20 km and 10–16 km from modern limits of two southern outlet glaciers from the icefield. Older full glacial limits are marked by moraines ca. 50 km from the modern glaciers. Inclusion in the glacial deposits of pumice clasts derived from an eruption of Reclus volcano at ca. 11,880 14 C years BP provides a close limiting age for the older Late-glacial event, while the younger advance occurred during the interval 11,880-9180 14 C years BP. It is argued that delgaciation occurred slowly in the Torres del Paine area because initial warming was accompanied by increased moisture as precipitation belts migrated southwards. Outlet glaciers then responded to subsequent cooling. Temperature depression is estimated to have been less than 2°C below current values, since Late-glacial moraines at some local glaciers lie within 200 m of the modern termini.