FORAMINÍFEROS DE AMBIENTE ANÓXICO DE LA FORMACIÓN RÍO MAYER (CRETÁCICO INFERIOR), PROVINCIA DE SANTA CRUZ

Abstract

FORAMINIFERS OF EUXINIC ENVIRONMENT FROM THE RIO MAYER FORMATION (LOWER CRETACEUS), SANTA CRUZ PROVINCE.- A fossil assemblage found in one sample from the upper part of the Rio Mayer Formation (Barremian, Pratian local stage) contains 28 calcareous benthic and one planktonic foraminifers and two ostracods. More than 90 % of the foraminifer specimens belong to Epistomina caracolla. It is not known if the lack of agglutinated foraminifers in this sample can be attributed to insufficient oxygen or to unavailabilíty of material to form the test. Cretaceous sediments of the Austral basin contain three maín foraminiferal associations, as follows: 1) agglutinated foraminifers, of flysh sequences, related to the Andean areas; 2) agglutinated foraminifers, of the Textularia-Spiroplectammina group, related to regressions; and 3) low díversity calcareous microfaunas contained in euxinic sediments, to which the material here described belongs.