Biostratigraphic and paleoceanographic analyses using planktonic foraminifers were made on a total of 148 samples from Ocean Drilling Program (ODP) Leg 170, Cores 170-1039B-1H through 18X (~160 m in thickness), and a total of 92 samples from Cores 170-1043A-18X through 30X (~130 m in thickness). The sediments from Cores 170-1039B-1H through 18X are assignable to Zones N19-N23 (Pliocene to Pleistocene) and sediments from Cores 170-1043A-18X through 30X to Zones N17-N23 (late Miocene to Pleistocene). In Zone N19, surface seawater temperature temporarily and abruptly drops and high salinity-tolerant species decrease. The divergence of both surface- and intermediate-water dwellers is recognized around the base of Zone N22. These changes in planktonic foraminiferal assemblages might be related to the closing of the Central American Seaway.
1Ibaraki, M., 2000. Pliocene-Pleistocene paleoceanography in the East Pacific off Costa Rica determined by planktonic foraminifers. In Silver, E.A., Kimura, G., and Shipley, T.H. (Eds.), Proc. ODP, Sci. Results, 170 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/170_SR/chap_06/chap_06.htm>. [Cited YYYY-MM-DD]
2Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan. sbmibar@ipc.shizouka.ac.jp
Initial receipt: 6 January 2000
Acceptance: 13 July 2000
Web publication: 13 October 2000
Ms 170SR-010