Late Quaternary megafans, fans and fluvio-aeolian interactions in the Bolivian Chaco, Tropical South America

Abstract

The Chaco is a huge plain and a main biogeographic biome of South America dominated by subtropical semi-deciduous vegetation that spreads on the Andes footslope on more than 800,000km 2 through Bolivia, Argentina and Paraguay. The climate is tropical wet-dry and the South American Summer Monsoon (SASM) leads to intensive convective rainfall during the summer season. Some of the world's largest river-fans such as the Parapeti and Grande rivers megafans developed in the Bolivian Chaco. Our research was based on morpho-sedimentary information and sustained by 25 OSL dating of fluvial and aeolian sediments. We demonstrate that these megafans are bigger than previously postulated by some authors...