Biostratigraphy of the quaternary nannofossils of the Campos Basin

Abstract

Seven biostratigraphic intervals have been identified through biostratigraphic studies based on calcareous nannofossils from samples of the Quaternary section of Campos and Santos basins. These intervals (named A to G) are based mainly on biological events such as extinction, first appearance, and prevalence (acme zone) of cosmopolitan taxa. In view of this, almost alI recognized sections have an identity with colval biozones that have been described in the bibliography, making easier their correlation with magnetastratigraphic units and the inference of absolute ages. Nevertheless, intervalo has not been consistently identified. According to what was observed it is possible to further divide the section. Such detailing would be based mainly on the appearance of Helicosphaera inversa (in interval C) and form B of H. carleri var. wallichii (al the base of interval F), and an the abundance of H. carteri s.l. (in interval G). It is possible that other subdivisions will be delineated through quantitative investigation. However, these would be based on "anomalous" concentrations of some species with strong environmental connotation. This is the case, for example, of sharp variations in the absolute frequency of Coccalithus pelagicus which, for the time being, have been detected in intervals F and G. According to the bibliography, this species altains maximum proliferation during glacial epochs.