UPPER QUATERNARY LANDSCAPE AND CLIMATE EVOLUTION IN THE NORTE CHICO (NORTHERN CHILE) - AN OVERVIEW

The distribution of geoecological units in the Norte Chico is the resu lt of a complex evolution, which is reconstructed here for Upper Quate rnary time, based on geomorphologic and pedologic studies. A humid pha se around 30,000 B.P. is documented within the Andes only, followed by arid conditions throughout the Norte Chico during the Last Glacial Te mperature Minimum (LGTM; 19,000 B.P.). The main phase of soil developm ent from the coast up to 3,400 m occurred during the Late Glacial peri od. Following that, the climate became more arid and warmer, manifeste d by a less dense vegetation cover and increasing influence of heavy r ains, leading to severe soil erosion and activation of alluvial fans. Outside the Andes these arid conditions prevailed during the Early- to Mid-Holocene, while above 2,500 m a warm Holocene climatic optimum ac companied by greater humidity is documented from the soils at that tim e; this indicates a strong contrast between the Andes and their wester n foreland. The present semi-arid conditions developed some 3,000 year s ago, leading to semi-stable geoecological conditions which have beco me increasingly influenced by human activity.