Primer registro de algas dulceacuícolas del Paleógeno de la Cuenca de Ñirihuau, Argentina: descripciones sistemáticas y análisis palinofacial

MARTÍNEZ, MARCELO A.; FERRER, NORA; ASENSIO, MARCOS

AMEGHINIANA

Asociación Paleontológica Argentina

Lugar: Buenos Aires; Año: 2008 p. 719 - 735

0002-7014

The first record of Paleogene freshwater algae from Ñirihau Basin is presented. The microflorawas recovered from the Salto del Macho Formation (Middle Eocene - Early Oligocene). Palynological and palynofacial analysis were carried out in order to establish the characteristics of the depositional environment. Thirteen taxa of Chlorophyta and Charophyta belonging to Botryococcaceae (Botryococcus sp. cf. B. braunii), Hydrodictyaceae (Pediastrumsp. cf. P. boryanum), Oedogoniaceae (Oedogonium sp. cf. O. cretaceum) and Zygnemataceae (seven species of Spirogyra, Lecaniella irregularis, Schizosporis sp. cf. S. reticulatus and gen. et sp. indet.) are described and illustrated. The palynological association suggests a freshwater, mesotrophic, shallow, probably stagnant and temporary body with neutral to slightly alkaline pH, under seasonally intense evaporation and temperate climatic conditions reaching, temperaturesover 20ºC. The palynofacies is dominated by amorphous organic matter of algal origin suggesting a reducing (at least temporarily disoxic-anoxic) environment under stagnant conditions. The low fluorescence suggests that the prevalent depositional conditions were not adecuate for kerogen preservation. The present data confirm the wider environmental variability of the Salto del Macho Formation, which varies from freshwater bodies (this contribution) to marginal-marineenvironments (previous record).