Abstract
A number of studies on lithostratigraphy and marine microfossil biostratigraphy has been conducted on the representative Pliocene to Lower Pleistocene formations in Japan. In recent years, new widespread tephra beds connecting the Pliocene to Lower Pleistocene formations in various areas have been discovered. The present work introduces the latest stratigraphic studies on the Pliocene to Lower Pleistocene formations in various regions. Further, it examines the relationship between extensive tephra beds as contemporaneous marker horizons and biostratigraphy of calcareous nannofossils and diatom fossils.