The planktonic foraminiferal biostratigraphy of Sites 1150 and 1151 drilled in the Japan Trench region during Ocean Drilling Program Leg 186 has been examined. At these drill sites, more than 1100 m of sediment, reaching to the middle Miocene, were obtained with good core recovery. Although planktonic foraminiferal records of the two sites are discontinuous, probably because of carbonate dissolution beneath the carbonate compensation depth, 16 stratigraphically important taxa of planktonic foraminifers were detected. Eight biohorizons were recognized in same stratigraphic order between these two sites. With respect to the diatom data, these eight planktonic foraminiferal biohorizons are possibly synchronous for correlating marine strata from the upper Miocene to Pleistocene in the Japan Trench region. The last occurrence of Neogloboquadrina asanoi falls within Olduvai Subchron. Therefore, the Pliocene/Pleistocene boundary of both sites is situated a little above this biohorizon.
1Hayashi, H., Morishita, C., and Oda, M., 2003. Neogene planktonic foraminiferal biostratigraphy of the Japan Trench, ODP Leg 186. In Suyehiro, K., Sacks, I.S., Acton, G.D., and Oda, M. (Eds.), Proc. ODP, Sci. Results, 186 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/186_SR/114/114.htm>. [Cited YYYY-MM-DD]
2Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan. Correspondence author: rin@mail.cc.tohoku.ac.jp
Initial receipt: 2 January 2002
Acceptance: 5 August 2002
Web publication:
20 February 2003
Ms 186SR-114