BIOESTRATIGRAFÍA DE LA FORMACIÓN SANTA CRUZ (MIOCENO INFERIOR) EN EL EXTREMO SUDESTE DE LA PATAGONIA

Abstract

"The Santa Cruz Formation is one of the South American stratigraphic units with more abundant and diverse of continental vertebrate fossils. Although, its palaeofauna is one of the most studied since the last century, biostratigraphic studies of this formation are really scarce. Two members have been recognized: a lower one, where pyroc1astic deposits and epiclastic claystones and mudstones with plenty of marnmalian fossils predominate; and an upper one, principally made of epiclastic claystones, mudstones and sandstones poor vertebrate remains. A biostratigraphic scheme is proposed based on 22 fossiliferous levels, 20 of which have vertebrate remains determinable at specific level as well as on the record of 60 species included into 44 genera, 25 families and 13 orders, representing arnphibians, birds and marnmals. Preliminary, two Interval Biozones, each based on one taxon, are distinguished: the Protypotherium attenuatum Biozone and the Protypotherium australe Biozone. Probably, two subzones can be reconognized in the former. The P. australe Biozone is coincident with the Protypotherium australe -Proeutatus oenophorus Association Biozone. "