CONICET | Buscador de Institutos y Recursos Humanos

We present a multi-proxy record from Laguna Nassau (LN), a shallow lake which developed in a blowout depression in the semi-arid sandy lowlands of the Western Pampas of Argentina . This multi-proxy stacked record reveals the evolution of an incipient water body subjected to warm and dry conditions from ~ 900 to 770 cal yr BP, an interval that is coeval with the Medieval Climatic Anomaly (MCA) period. Vegetation was dominated locally by Typha, and regionally by the Espinal, represented by Celtis, along with psamophytic-halophtytic communities in sand dunes and lowlands. After that, variable depth and unstable conditions occurred in the water body in relation to dry and humid climatic phases until ~ 200 cal yr BP, likely related to a transition from warm and dry conditions, corresponding to the MCA, to colder and wet climatic setting during a period concurrent with the Little Ice Age (LIA). This water body evolved into a shallow lake since then, with a more stable and deeper water level, and regional vegetation characterized by the Espinal and psammophytic-halophytic communities mantling and stabilizing the nearby sand dunes. This evolution suggests complex hydrological responses of LN likely associated with its sensitivity to climatic variability. Comparisons of our records with others from the western and northeastern Pampas showed that, despite different levels of chronological resolution, the environmental, hydrological and climatic conditions during MCA and LIA were not uniform and included dry and wet phases with different timing at the regional scale. Nevertheless, we found that the climatic variations recorded at LN are more similar to those of Salinas del Bebedero, a playa lake located to the west of LN. In contrast, of the climate record of Laguna Mar Chiquita, located at the northeastern Pampas supports a different east-west hydrological regime in the Pampean Plain.