Preliminary report on the Tertiary larger foraminiferal biostratigraphy in Chichi-jima (Peel Island) and Haha-jima (Hillsborough Island), Ogasawara Islands, Japan

The Tertiary larger foraminiferal biostratigraphy of Chichi-jima and Haha-jima is examined and preliminary discussed. In Haha-jima, two larger foraminiferal horizons are existed at least as follows: Discocyclina (s.l.)-bearing rocks and Nummulites boninensis-bearing rocks in descending order. From the Minamizaki Limestone distributed in Minamizaki, southwest part of Chichi-jima, three larger foraminiferal zones are defined as follows: Nephrolepidina Zone, Spiroclypeus-Miogypsinoides Zone and Eulepidina Zone in descending order. Moreover, two letter stages of Tertiary e 1-4 and Tertiary e 5, respectively are recognized from the stratigraphical position of the extinction of Heterostegina borneensis into the Spiroclypeus-Miogypsinoides Zone