Optical microscope revision of the morphostructural features of nannoliths Incertae Sedis presenton Paleocene/Middle Eocene section of the Espírito Santo Basin

Abstract

Most of the nannolith species described in this paper present undoubtedfy biostratigraphic importance both in international and PETROBRAS biozonal schemes. In the latte, they are used in routine dating of Paleogene strata in Brazilian marginal basins. The studied nannofossils have all been recovered from cuttings of lhe Paleocene /Meso Eacene section of wells in the Espírito Santo Basin (eastem Brazilian continental margin). The basic aim of this study is to present detailed O.M. (optical microscope) descriptions of these calcareous nannofossils in arder to optimize their use in the routine biostratigraphic dating. Altogether. nine species have been identified, of which one is new( Ellipsolithus  gomidel) , and two other are recorded for the first time in Brazil (Ellipsolithus bollii and Trochastrites hohnensis). The identified species belong to the following genera: Ellipsolithus, Nannotetrina, Tribrachiatus, and Trochastrites. All of them are considered incertae sedis. because they can not be assigned to any nannofossil families recognized so far.