Climatic changes in the South American plains: Records of a continent-scale oscillation

The last glacial/interglacial cycle produced a variety of climates and land scape responses in South America. The present contribution is an attempt to establish broad trends within this complex period. Two points are clear: ( a) In the Cordillera de los Andes temperature variations produced advances and retreats of glaciers, which were coherent with the global climatic chan ges recorded in other continents. (b) The lowlands experienced a series of dry and humid periods. Humid intervals in the north of the continent (exten ding to latitude 10 degrees S) are coeval with dry conditions in the south and vice versa. The broad climatic sequence is as follows: Isotope stage 4 - A massive glaciation affected the whole Cordillera. Humid climate in the north. A large desert developed in the south, associated wi th wind-blown silts which reached a latitude of 25 degrees S in SE Brazil. Isotope Stage 3 - Mountain glaciers were of modest extent in the Andes. A h umid climate with soil development and dune degradation prevailed in the so uth (Pampa and Chaco) while dry conditions dominated the north (Colombia an d Amazonas). Isotope Stage 2 - General advance of glaciers in the Andes, although smalle r than in IS4. Dry and cold in the south, with extension of the Patagonian climate to the NE. Humid in Amazonas. The waning of the glaciation was acco mpanied by a humid environment (pedogenesis) in the Pampa and by a dry phas e in the north (forest retreat in Carajas and in the Colombian Andes). With in the period 14,000 BP to 8500 BP (sensu late Younger Dryas) a glacial adv ance occurred, with humid conditions in the north (pedogenesis in the Orino co and forest readvance in Amazonas) and a dry climate characterized by str ong westerly winds in the Pampa. The Hypsithermal period was humid in the south and dry in the north of the continent. (C) 1999 INQUA/Elsevier Science Ltd. All rights reserved.