石灰質ナンノプランクトンによる第四系化石帯区分  [in Japanese] Calcareous nannofossil zones of the Quaternary  [in Japanese]

Twelve calcareous nannofossil biohorizons were recognized in the Quaternary sequences at six sites drilled in the Northeast Atlantic Oeean during DSDP-IPOD Leg 94. Correlation of these biohorizons with the magnetostratigraphy was also established for the same cores, and ages of all these biohorizons were estimated by interpolation between magnetic reversals (TAKAYAMA and SATO, 1987). The calcareous nannofossil assemblages of the Quaternary sequences distributed in the Oga Peninsula, Akita and Niigata 0il fields, Kanazawa area and the Boso Peninsula were studied. The most of these calcareous nannofossil biohorizons abovementioned were detected in these sequences. We clarified the relationships of coc-colith bio- and magnetostratigraphy and radiometric age assignments of the sediments in these areas and demonstrated the usefulness of nannofossils as biostratigraphic indicators.