EVOLUTION OF EARLY PLEISTOCENE DEEP WATER CIRCULATION IN WESTERN PACIFIC: EVIDENCE FROM BENTHIC FORAMINIFERA

Benthic foraminifera picked out from the interval of 43.02~26.27 mbsf (meters below seafloor) of ODP 807(3°36.42'N,156°37.49'E,water depth 2 803.8 m,length 822.9 m)on the Ontong-Java Plateau, western Pacific was studied for understanding the changes in paleoproductivity and its relation with deep water circulation during the period of 2.5~1.6 MaBP. The benthic foraminifera accumulation rate (BFAR), Epifaunal/Infaunal ratio (E/I), percentage of Uvigerina spp. and total organic carbon (TOC%) were used as the proxies of paleoproductivity in this study. Results show that the change in paleoproductivity was generaly high in glacials but low in interglacials during the period of 2.5~1.6 MaBP., except Bulimina alazanensis, of which the paleopruductivity was low in glacials but high in interglacials. It may suggest that B. alazanensis, opposite to the others, preferred a warmer environment with lower nutrients. The benthic foraminiferal fauna was dominated by Uvigerina spp. in the samples, indicating that the western Pacific deep water was under the control of the North Pacific Deep Water Mass during Early Pleistocene.