Foraminíferos del Oligoceno inferior de los Andes Fueguinos, Argentina: su significado tectónico-ambiental

two early oligocene assemblages of calcareous foraminifera from the estancia maría cristina beds, critical in the chronology and paleoecological events of the fuegian andes, are described. these assemblages indicate the environmental setting and the early oligocene age of the beginning of the deepest foredeep in the upper cretaceous-miocene of the fuegian andes and mark out the age of the fuegian fold-thrust belt. these beds were deposited mostly below the compensation calcite depth and bear mainly agglutinated foraminifera that testify the incursion of corrosive antarctic waters. from restricted levels that have escaped to dissolution inland and near to the farm, one of the assemblage was recovered, it is composed of abundant planktonic foraminifera typical of high latitude dominated by subbotina angiporoides and catapsydrax dissimilis, which together with "chiloguembelina" cubensis and the nannofossil isthmolithus recurvus, indicate an age between 30 and 34 ma (lower part of the zone of subbotina angiporoides, or antarctic zone ap13); the co-occurring benthic foraminifera are dominated by uvigerina subproboscidea. another calcareous assemblage was recovered from an horizon of a section on the atlantic coast, near cerro colorado; which is composed of a similar planktonic assemblage and an outer shelf benthic calcareous association strongly dominated by globocassidulina pseudocrassa and with abundant u. subproboscidea and stilostomella spp. it is remarkable that at least in the mid-high latitudes of the southern hemisphere, "chiloguembelina" cubensis and chiloguembelina ototara are morphologically and chronologically differentiable species, the former one restricted to the oligocene and the latter one mostly to the upper eocene.