CONICET | Buscador de Institutos y Recursos Humanos

The sedimentary record of Melincué Lake (33°S/61°W), an alkaline and shallow lake located in central Argentina is analyzed to disentangle past and present hydroclimate variability. In this area, changing precipitation-evaporation ratios are ruled by the variability of the South America Monsoon system. A dataset including elemental X-ray fluorescence variations (Ca, Sr, Al, K, Si, Ti and Fe), physical properties (magnetic susceptibility and dry bulk density) and carbon and nitrogen contents, is analyzed and contrasted with instrumental information from Melincué Lake in order to reconstruct the main hydroclimatic changes from the Little Ice Age (LIA) to the Current Warm Period (CWP). Very low sedimentation rates and discontinuities indicate episodes of probable lake-floor subaerial exposures and ephemeral conditions that prevented a long time-scale model for the LIA period. Historical documents and deposits of organic matter-poor and massive sediments evidence the development of very shallow lake conditions by the end of the LIA. Bedded and laminated organic-rich muds accumulated after ca. AD 1880 reveal an environmental shift into perennial lake conditions concurrent with the onset of the CWP. Sediment composition and instrumental record during the 20th century indicate enhanced detrital input and carbonate precipitation processes occurred during shallow saline-lake stages in dry periods. In turn, enhanced organic lake productivity and lower carbonate precipitation were promoted during higher lake levels in wetter phases. This reconstruction with decadal resolution in the CWP provides data to evaluate regional hydroclimate models and environmental changes in central Argentina related to the dynamics of the South American Monsoon system.