OSTRACODOS DE LA FORMACION ÑIRIHUAU (OLIGOCENO), CUENCA DE ÑIRIHUAU-ÑORQUINCO-CUSHAMEN: SIGNIFICADO PALEOAMBIENTAL

Abstract

The ostracods of the Ñirihuau Formation found around the outskirts of San Carlos de Bariloche, Río Negro Province, Argentina, are analyzed. The preservation of the ostracods is very poor presenting closed, recrystallized and deformed carapaces. The identified species are: Eucypris? sp., Candona? sp., Limnocythere? sp., Chlamydotheca? sp. and Darwinula sp. These ostracods are typical of limnic environments. The assemblages show either a reduced number of species, or a dominant taxon in certain leveIs. The presence of these assemblages and/or monofaunas with Eucypris? sp., Candona? sp. and other species on the one hand, and Dorwinula sp. on the other, suggests not only that each assemblage excludes the other, but also that their presence in the sediments are the result of changes of energy in the rythm of sedimentation. KEY WORDS. Argentina. Río Negro Province. Ñirihuau Formation. Oligocene. Ostracoda. Palaeoecology.