Dunes and dunefields in the Bolivian Chaco as potential records of environmental change
Eastern Bolivia is situated along the southern margin of the Amazon basin where climate is characterized by the strong hydroclimatic seasonality and high wind speeds related to the South American Low Level Jet (SALLJ). In this setting, this paper explores the geomorphology and environmental significance of the aeolian record in the Bolivian Chaco. Based on the analysis of remote sensing imagery, 10 dunefields were mapped. Their size, topography and geomorphic setting reflect long-term interactions with the fluvial system in the Andean foreland. Preserved aeolian morphology includes different types of linear sand streaks and ridges, parabolic and elongate parabolic morphologies, source-bordering dunes, sandsheets, and transverse dunes and/or mega-ripples. This detailed local to regional-scale geomorphic dataset thus provides the necessary base for the establishment of a chronological framework of dune activity versus stability, and the mapping results reflect the spatial and temporal variations of aeolian processes and their environmental controls such as wind, vegetation, and sediment supply. Compared to the extensive area covered by inactive aeolian features, the localized modern dune activity implies that environmental conditions were more conducive for the expansion of dunefields during some periods in the late Quaternary, while the predominance of parabolic forms reflects the variable but persisting control of vegetation on dune formation in the Bolivian Chaco.