Late-Holocene paleolimnological study of a shallow-lake at the Pampa grasslands (Laguna La Brava, Buenos Aires, Argentina)

PRIETO A.R.; IRURZUN M.A.; GOGORZA C.S.G.; CHAPARRO M.A.E.; NAVAS A.; LIRIO J.M.; SINITO A.M.

La Plata (Argentina)

Congreso; IV Congreso Argentino de Cuaternario y Geomorfología, el XII Congresso da Associação Brasileira de Estudos do Quaternário y la II Reunión sobre el Cuaternario de América del Sur; 2009

AACyG - ABEQUA

Laguna La Brava (37º 52’S; 57º 59’W) is one of the freshwater shallow-lakes of the Pampa grasslands classified as permanent because it has never dried up during historical times (Dangvas, 2005). This allowed the sampling of continuous long cores for paleolimnological studies. This shallow lake (4.5 km2) has had significant water level fluctuations related to both hydrometeorological conditions and to human activities. We have used pollen and no-pollen palynomorphs (NPPs), magnetic susceptibility, grain size analysis, total organic carbon (TOC) and total sulphur (TS) from a 550 cm long core (Br-4) to evaluate the potential usefulness of these proxy data for paleolimnological reconstruction. The chronology is based on five AMS-radiocarbon dates. A temporal extent of 4700 calendar years has been calculated for the core. The sedimentary accumulation rate averaged 1.22 mm/yr. Relationships between pollen from emergent, floating-leaved and submerged aquatic macrophytes, NPPs (green algae, cyanobacteria and fungal spores), geochemical, magnetic and sedimentological data have been analysed to infer lake-level fluctuations, trophic conditions and precipitation changes.