South American Great Basin: Limnogeological analysis of the Salina del Bebedero Basin, Argentina (Late Pleistocene-recent)

Abstract

The Bebedero tectonic depression in San Luis province, Argentina, is a closed drainage basin that has formed as a result of block-faulting and rifting processes. The Bebedero lake exhibits notable similarities to the endorheic watersheds of the western United States, particularly those of Death Valley, the Saline Valley and, to a lesser extent, the Great Salt Lake. While it is currently classified as a playa lake, there is evidence of lake levels near the sill that overflowed during the Late Pleistocene. Several lines of evidence suggest that climate is the major controlling factor in the basin's fill. The Salina del Bebedero Basin is an underfilled lake basin type, particularly a discharge lake basin. This assertion is supported by recent findings, including precise topography, stratigraphy, facies associations, radiocarbon ages and palaeontology from one section and two transects. The following presentation comprises stratigraphic correlations, palaeoenvironmental reconstructions and a graphical model of lake stages based on these new results and previously published research. This paper provides a model of lake-level fill from the Late Pleistocene to the present, identifying distinct highstands and lowstands associated with global climate events. The surface and depth of the lake were reconstructed for each stage. The maximum expansion was estimated at 1000 km² during the Pre-Last Glacial Maximum and 782.6 km² during the Last Glacial Maximum, with depths ranging from 60 to 75 m. Lake Bebedero exhibited similar lake-level responses to climate variations as Lake Bonneville, Great Salt Lake, as well as sub-environmental similarities with Death Valley and the Saline Valley. In addition to its palaeoclimate significance, Lake Bebedero has archaeological records of an early settlement dating back ca 10 to 6 cal ka BP. The scarcity of data concerning the early human settlement in southern South America makes archaeological evidence relevant. Therefore, the inferences regarding climate and environment derived from studies of the lake provide important information about the first human groups to populate these regions.