Late and postglacial vegetational and paleoclimatic changes in subantarctic, temperate, and arid environments in Argentina

Abstract

A paleoclimatic chronology for southern South America is suggested by comparison of dated pollen records from Argentina (lat 32° to 34°S, 41°S and 51° to 54°S). The paleoenvironmental phases distinguished for the last 13,000 years are interpreted as paleoclimatic phases and explained as latitudinal shifts of atmospheric circulation anomalies by using the correlation of modern precipitation patterns with atmospheric circulation anomaly patterns over Argentina and Chile. The lateglacial type environment is characterized at all sites in the high southern latitudes by pollen assemblages of grasses, composites, sedges, and heath, suggesting climates as cold and wet as the modern Magellanic Moorland uniformly throughout Tierra del Fuego and southern Patagonia. At latitude 41°S the lateglacial pollen assemblages are dominated by rainforest types west of the Andes, suggesting cold and wet conditions, while east of the Andes grasses and herb pollen dominated the assemblages, suggesting conditions colder and drier than today. Lateglacial pollen assemblages at latitude 32°S are dominated by grasses, composites, and desert shrub pollen, suggesting colder and wetter climates than today. Postglacial type environments replaced the lateglacial ones at 12,000 yr B.P. at latitudes 32° and 41°S, but only at 8,500 yr B.P. at latitudes 51° to 54°S. The postglacial environments at all latitudes resemble the modern environments, with Nothofagus pollen dominating at high southern latitudes and latitude 41°S and desert scrub pollen at latitude 32°S, suggesting precipitation and temperature values similar to the modern ones. Environmental changes during the Holocene occurred at 8,500 yr B.P., 6,000 yr B.P., 5,000 yr B.P., and 3,000 yr B.P., but are of much smaller amplitude than the change from lateglacial to postglacial environments.