Quaternary lacustrine ostracods: their use in inferring patagonian paleoenvironments.

CUSMINSKY, G

La Plata

Taller; Taller Paleogeografía y paleoclimatología de la Patagonia: sus efectos sobre biodiversidad.; 2009

Facultad de Cs Naturales y Museo/CONICET

Ostracods are small bivalve crustaceans that are found in all kinds of aquatic environments. Physicol-chemical parameters such us water temperature, pH, salinity, dissolved oxygen, nutrient levels and sediment type control their abundance. Thus, ostracods are very usefull as paleoenvironmental indicators, especially for the recontruction of non-marine Quaternary paleonvirobnments. Systematic and isotopoc studies of Recent ostracods in different areas of Patagonia have allowed to identify associations which are related to environmental parametes. Thus, certain ostracod associations could be recognized in the following environments: 1) spring, ponds or small creeks, characterized by the presence of Darwinula sp, Heterocypris incongruens (Ramdohr); Eucypris fontana (Graf), Amphicypris nobilis Sars and Ilyocypris ramirezi Cusminsky and Whatley; 2) lakes and permanent ponds, with Limnocythere patagonica Cusminsky and Whatley, E. labyrinthica Cusminsky and Whatley, Limnocythere sp and E. fontana as typical species and 3) ephemeral lacustrine environments, characterized by the presence of Limnocythere rionegroensis Cusminsky and Whatley as the dominant species. These associations were recognized both in Late Pleistocene as Holocene sequences of Patagonia, for instance in outcropos of the Cari-lafuquen area , Río Negro , and in cores of Lago Cardiel, Santa Cruz. The variability bhoth in abundance as in the species association along the studies sequences, particularly referring to permanent and ephemeral environments, suggests that in may be showing large climatic variations in the regions during the Late Quaternary