Multiproxy study of past three centuries of climatic variability and anthropogenic impact on Laguna Pocitos,western Pampa of Argentina

Abstract

The northern sector of the Western Pampean Dunefield (central Argentina), characterized by Late Quaternary to Late Holocene aeolian morphogenesis and sedimentation under drier conditions than present, hosts numerous shallow lakes developed in the deflation basins of blowout dunes. A multi-proxy analysis, including magnetic susceptibility, charcoal, C and N content, stable isotopes, and pollen and non-pollen palynomorphs, was performed on a sediment core from Laguna Pocitos (33° 58.2’S – 65° 34.3’W) to contribute to paleoenvironmental and paleoecological reconstructions of the region. The integrated evidence allows inferences about environmental variability over the past ~350 years (~1670–2015 CE), including the impact of natural and anthropogenic forcings. The first recorded period (~1670–1758 CE) reveals rising water levels under drier conditions than today, with intense fire events within a grassland-dominated landscape. Frequent water level fluctuations were inferred for the next 100 years (~1760–1870 CE), accompanied by diminished grassland cover and more disturbance taxa associated with an increasing anthropogenic presence in the area. After ~1870 CE, a trend toward lower water levels coincides with widespread droughts that culminate in the historically and geologically recognized Pampas Dust Bowl. Since ~1970 CE, multiple core indicators evidence a lake expansion, consistent with remote sensing data and instrumental records. This phase was characterized by clear water conditions synchronous with an intensification of anthropogenic pressure. Overall, hydroclimatic variability inferred from the Laguna Pocitos record is coherent with historical documents and paleolimnological reconstructions from the Pampa plain, revealing the control of regional climate pattern but including distinctive local modulation which needs further studies.