FORAMINIFEROS (PROTOZOA) y OSTRACODOS (ARTHROPODA) DE LAS "LUTITAS DE RIO FOYEL" (OLIGOCENO) DE LA CUE CA DE ÑIRIHUAU, PROVINCIA DE RIO NEGRO, REPUBLICA ARGENTINA

S. A. BERTELS

Abstract


Chronostratigraphic, paleogeographic and paleoeco logical aspects of the marine sediments informally known as "Foyel River Shales" are inferred. The strata belong to the Leonian Stage and are equivalent to the type Upper Lattorfian and Chattian Stages, although the upper levels could be earliest Miocene in age. This marine sedimentary basin was probably fonned during late Eocene times. Epeirogenic movements, which occured during the early Oligocene, caused the deepening of the Austral Basin and its connection with the Ñirihuau basin at the time of the deposition of the Leonian Stage. The Ñirihuau assemblage shows depositional features of restricted sea conditions and a gradual shaJlowing of the water mass.

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