Irregular End-Pliocene Discoasters in Sediments of the Southwest Atlantic

Abstract

Nannofossils were studied, recovered from Late Pliocene–Pleistocene sediments at station 3316 on cruise 46 of the R/V Akademik Ioffe north of the Rio Grande Rise in the Southwest Atlantic. The presence of irregular discoasters in a narrow horizon at the end of the Discoaster brouweri zone of the Upper Pliocene indicates dramatic changes in the living conditions of these organisms, which led to deviations in the regular structure of their skeletons and subsequent extinction at the end of the Pliocene.