Calcareous nanno plankton bio stratigraphy around the pliocene pleistocene boundary in the southern part of okinawa jima japan

Nishida, S.

Journal of the Geological Society of Japan 86(8): 525-536

1980


ISSN/ISBN: 0016-7630
Accession: 004865663

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Abstract
Calcareous nannoplankton biostratigraphy around the Pliocene-Pleistocene boundary in a sub-tropical land-based section was revealed with scanning electron microscopy. Studied sequences develop in the southern part of Okinawa-jima, stratigraphically ranging from the Pliocene Shinzato Formation up to the Pleistocene Chinen Sand. Their boundary is between underlying cross-laminated gray fine sandstone and overlying light brown sandstone and situated 2.5 m above the Kudeken Tuff. Calcareous nannoplankton events (7) were recognized: the disappearance of Discoaster pentaradiatus, the appearance of Acanthoica quatrospina, the occurrence of Gephyrocapsa caribbeanica, the appearance of G. protohuxleyi, the disappearance of Cyclococcolithus macintyrei, the extinction of D. brouweri and the 1st appearance of G. oceanica in ascending order. The extinction of D. brouweri and the 1st appearance of G. oceanica are noticeable in relation to the 1st appearance of planktonic foraminifer Globorotalia truncatulinoides and the paleomagnetic Olduvai Event. These micropaleontological events around the Pliocene-Pleistocene boundary are discussed, and time-transgressive appearance of G. oceanica is suggested.