Palaeoenvironmental record of Laguna Llancanelo, Argentina, since the Late Pleistocene

D'AMBROSIO, SABINA; GARCIA, ADRIANA; CHIVAS, ALLAN; CLAPS, MARIA CRISTINA

Congreso; 34th International Geological Congress; 2012

Palaeoenvironmental record of Laguna Llancanelo, Argentina, since the Late Pleistocene Sabina D´AMBROSIO1,2,*, Adriana GARCIA2,*, Allan R. CHIVAS2, Cristina CLAPS1. 1CONICET-ILPLA. Facultad de Ciencias Naturales y Museo, Universidad Nacionalidad de La Plata, Argentina. email: sabina.dambrosio@gmail.com. (*PICT 2006-1311 Agencia Nacional de Promoción Científica y Tecnológica.); 2GeoQuEST, School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia This project reconstructs the palaeoenvironments/palaeoclimate of the Laguna Llancanelo area based on ostracod associations and geochemistry. Laguna Llancanelo (Provincial Reserve, Ramsar Site) is located ~ 400 km south of Mendoza at 1330 m a.s.l and 70 km east of the Andes. The lake developed in an endorheic basin, within the Llancanelo-Payenia volcanic field, is saline and has a mean water depth of 30 cm (deepest area reaches 170 cm). Nine undisturbed sediment cores were extracted by vibracoring. The results of this paper are based on analysis of a 9 m long core from the western shore, representing approximately 30 ka. Samples for sedimentological and micropalaeontological analyses were taken each 10 cm. Fresh to saline facies have been recognised, as well as a distinct pre- and post-LGM ostracod fauna, the former represented by Limnocythere sp.1, several Cyprididae and Darwinula stevensoni amongst others, which were later replaced by Limnocythere cf. staplini, Darwinula stevensoni, Alicenula nov. sp., Candonocypris spp., and Sarcypridopsis sp.. Almost all the levels have an ‘in situ’ ostracod assemblage (all instars present). A preliminary conclusion indicates that before 20 ka the lake was fresher/larger in extent and that during the Holocene the lake became more saline with an increasing influence of El Niño/La Niña events, with i.e. gypsum increasing variably towards the top. Further studies will involve statistical analyses (i.e. cladistic analyses) of the ostracods, as well as ICP-MS analyses of the valves (Sr/Ca, Mg/Ca, Ba/Ca) to determine past salinities, temperature, and pH.