Calcareous Nannoplankton Fossils and their Stratigraphic Meaning

Abstract

Modern calcareous nannoplanktons have an important role in marine food chain as a primary producelr. Fossils nannoplankton played an important part of the Mesozoic and Cenozoic biological world, and are now accepted as a very useful and accurate index fossil from the Jurassic to Recent Period.In this article recent advance of nannoplankton micropaleontology and biostratigraphy were briefly reviewed. And a calcareous nannoplankton biostratigraphy of the Upper Cenozoic sections in Japanese Pacific coast was presented.In the sections drastic changes of some calcareous nannoplankton species are recognized clearly ; that is, the first appearances of Reticulofenestra japonica, Gephyrocapsa caribbeanica, Gephyrocapsa oceanica, Gephyrocapsa protohuxleyi and Emiliania huxleyi in ascending order, and the disappearances of Sphenolithus abies, Reticulofenestra pseudoumbilica, Discoaster surculus, Discoaster pentaradiatus, Discoaster brouweri, Cyclococcolithus macintyrei. Cyclolithella annula, Reticulofenestra japonica, Reticulofenestra pacifica and Pseudoemiliania lacunosa in ascending order.Based on the first appearances of these species, we can distinguish five calcareous nannoplankton zones in Japan ; that is, Reticulofenestra pseudoumbilica Zone, Reticulofenestra japonica Zone, Reticulofenestra pacifica Zone, Gephyrocapsa oceanica Zone and Emiliania huxleyi Zone in ascending order.Range chart of some important species and calcareous nannoplankton zonation are presented in figure 3, and a stratigraphic correlation is also shown in figure 4.