MIDDLE EOCENE - OLIGOCENE GASTROPODS OF THE SARMIENTO FORMATION, CENTRAL PATAGONIA

MIQUEL, S.E.; BELLOSI, E.S.

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia. eds. R. Madden, A. Carlini, M. Vucetich and R. Kay. Cambridge University Press.

Cambridge University Press

Lugar: Cambridge; Año: 2010; p. 61 - 68

Diverse fossil gastropods are preserved in the lower and middle sections of the continental Sarmiento Formation in Chubut Province, Argentina. The assemblage is dominated by land specimens assigned to five families (15 genera). A new genus and species of Charopidae,Colhueconus simpsoni, is described. The presence of Austroborus sp. (Strophocheilidae) and Plagiodontes sp. (Odontostomidae) is noted for the first time. Stratigraphic distribution and ecological affinities with related living specimens allow us to infer that warm–temperate andhumid environments prevailed in the late middle Eocene (Casamayoran SALMA), with species of Strophocheilidae, Orthalicidae, and Chilinidae. In the Mustersan SALMA (middle–late Eocene) a significant increase in diversity is observed, mostly dominated by Charopidae, which indicates cooler conditions in accordance with the global climatic trend. The absence of gastropods in Tinguirirican SALMA deposits could be related to the enhanced cooling and drying at the terminal Eocene – early Oligocene. The fauna preserved in Deseadan SALMA beds (late Oligocene)is similar but less diverse than the Casamayoran fauna, indicating a return to probably locally wetter and warmer conditions.