Eocene land microgastropods (Pulmonata, Charopidae) of the Sarmiento Formation at Gran Barranca (Central Patagonia)

MIQUEL S.E. AND E.S. BELLOSI

La Plata

Congreso; XV Congreso Geológico Argentino; 2005

Asociación Geológica Argentina

ABSTRACT The Sarmiento Formation possesses an unusually rich record of terrestrial microgastropods, recovered from a massive and thick calcrete horizon of the Rosado Member (Middle-Late Eocene). This interesting and unique assemblage of microgastropds includes ten species: the oldest record of the genera Rotadiscus, Stephadiscus, Stephanoda and Zilchogyra, and the first Paleogene record of Radiodiscus. Other records of this family are few and far between, and are only known from the Miocene of Polynesia and the Pleistocene of North America. The fossil assemblage includes species closely related to recent living Argentine species, particularly those that occur in Andean NW Patagonia and farther south in the Magellanian region. This stock also shows affinities with faunas from New Zealand, Tasmania and Australia. Rosado Member microgastropods suggest a humid cool-temperate climate, probably with brief fluctuations to warmer conditions. Rotadiscus, Stephadiscus, Stephanoda and Zilchogyra, and the first Paleogene record of Radiodiscus. Other records of this family are few and far between, and are only known from the Miocene of Polynesia and the Pleistocene of North America. The fossil assemblage includes species closely related to recent living Argentine species, particularly those that occur in Andean NW Patagonia and farther south in the Magellanian region. This stock also shows affinities with faunas from New Zealand, Tasmania and Australia. Rosado Member microgastropods suggest a humid cool-temperate climate, probably with brief fluctuations to warmer conditions.