Late Quaternary environmental changes in patagonia as inferred from lacustrine fossil and extant ostracodes

CUSMINSKY , G. C.; SCHWALB, A; P. A. PÉREZ; PINEDA, D; VIEHBERG, F; WHATLEY R.; MARKGRAF, V; GILLI, A; ARIZTEGUI, D; ANSELMETTI, F

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: London; Año: 2011 vol. 103 p. 397 - 408

0024-4066

We compare modern and Quaternary ostracodes from two lacustrine basins, Laguna Cari-Laufquen (41¨¬S) and Lago Cardiel (49¡ÆS) in Patagonia. Taxonomic and quantitative analyses along with isotopic and chemical studies of the extant ostracode fauna indicate that distinct ostracod associations can be identified as a function of conductivity. Three ostracod associations can be distinguished: 1) springs, ponds and small creeks, characterized by low conductivity (e. g. 1015 ¥ìscm-1); 2) lakes and permanent ponds, characterized by medium conductivity (e.g. 1625 ¥ìscm-1) and 3) ephemeral lacustrine environments, generally characterizerd by higher conductivity (e.g. 16480 ¥ìscm¡©1) These modern ostracod associations were also identified in older sequences from sediments outcropping in the Laguna Cari-Laufquen current shoreline as well as in sediment cores from Lago Cardiel. The predominance of Limnocythere rionegroensis Cusminsky & Whatley in the Cari-Laufquen sections suggests the development of a saline and turbid lake during the Late Pleistocene and Early Holocene suggesting higher precipitation at these latitudes. Changes in ostracode abundance and associations have been observed in Lago Cardiel during the last ~16,000 cal yr B.P . Conductivity is known to change as a function of the ratio of precipitation to evaporation (P/E) and a decrease in conductivity from the Late Pleistocene to the Middle Holocene suggests substantial hydrological variations (i.e. increase of the precipitation/evaporation ratio suggests minor conductivity). These two examples show that ostracodes provide an excellent proxy for interpreting paleoclimatic and paleoenvironmental changes in Patagonia.