Southern South American hydroclimatic units, their recent continental ostracod association characterisation: useful for palaeohydrological studies

Southern South America is known for its extensive arid and semi-arid regions, determined by it is current geography and the Andes mountain range in it is western part. This work consists of six parts: (1) sampling of ostracods and water physicochemical parameters from 51 sites, (2) statistical analysis to establish the relationships of ostracod associations to each type of environment, (3) determination and delimitation of hydroclimatic units, (4) compilation of published ostracod works in Argentina, (5) characterisation of each hydroclimatic unit by an exclusive ostracod assemblage, and (6) determination of ostracod species as palaeohydrological indicators. The results show that the main factors influencing the separation of the different environments were the water salinity, the altitude and the Ca concentration. This study allows the division of Argentina into three major units based on climatic conditions, geological characteristics and hydrological catchment delineation. These units have been designated as hydroclimatic units characterised by an ostracod assemblage of at least 12 exclusive species. Thus, ostracods are good indicators of environmental characterisation and the exclusive ostracod assemblage in each hydroclimatic unit are useful as modern analogues. The present contribution will help to better understand the changes that occurred during the glacial/interglacial periods, responding to the current climatic changes. Palaeolimnological reconstructions can now be made more precise by relating basin types, environments present, climates and ostracod assemblages.