Glacial, vegetational, and climatic history in Torres del Paine National Park since 14, 000 years BP: the Vega Ñandú record
by
Rodrigo Villa Martínez
Centro de Estudios del Cuaternario, Universidad de Magallanes, Punta Arenas, Chile
Coauthors: Patricio I. Moreno (Departamento Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Chile)

The Vega Ñandú site (50º55’58’’S; 72º45’55’’W; 200 m elevation), located in the Torres del Paine area, shows ~8 m of laminated glaciolacustrine mud, deposited in a small lake dammed by the Río Paine ice lobe during the D stage (Marden, 1997). An abrupt concordant transition gives way to a ~4 m-thick organic unit that spans the last 12,600 years. This transition implies that the ice-dammed lake disappeared as the Río Paine ice lobe abandoned the D position, most likely driven by a warming event.

A high-resolution pollen and charcoal record was developed on the organic unit to document the vegetation, fire, and climate history in an area adjacent to the modern forest-steppe ecotone. The record shows an open landscape dominated by Gramineae, low shrubs, and herbs between 12.6-10.8 ka (ka: 1000 cal yr BP), thus suggesting scrubland-steppe vegetation under cold/dry conditions. An abrupt and variable expansion of Nothofagus occurred between 10.8-7.8 ka, implying a highly dynamic woodland with intense fire activity, and/or frequent shifts in the forest-steppe ecotone. Climate conditions during this interval are interpreted as warm and humid. A gradual and sustained increase in Nothofagus started at 7.8 ka, punctuated by an abrupt rise at 3.7 ka implying further increases in westerly precipitation, and an eastward shift in the forest-steppe ecotone that persisted until ~1890 AD. Severe fire disturbance and livestock grazing over the last 100 years led to a decline in forest cover and the establishment of an “anthropogenic steppe”.

In summary, our results suggest that: (i) glacial recession in Torres del Paine coincided with the onset of the Younger Dryas and the end of the Antarctic Cold Reversal; (ii) precipitation increased in discrete pulses at 10.8, 7.8, and 3.7 ka, and (iii) the modern forest-steppe ecotone in this area is largely the result of European disturbance. Financial support: Fondecyt 1040204, NGS 7416-03, Iniciativa Científica Milenio P02-051.

Marden, C. (1997). Late glacial fluctuations of South Patagonian Icefield, Torres del Paine National Park, Southern Chile. Quaternary International 38-39, 61-68.

Date received: November 20, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caod-41.