|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1998 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1997 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1996 : ¥1,100,000 (Direct Cost : ¥1,100,000)
AMS 14C dating on more than 20 horizons of three cores raised from the continental slope of the eastern East China Sea (ECS) revealed that cores KH82-4-14 and BO94-20 PN-3 contain continuous records of the last 24, OOOyrs, while core RN8O-PC3 covers the last 14, OOOyrs. Three faunal phases distinguished by characteristic downcore planktic foraminiferal assemblages suggest three major paleoenvironmental stages of the surface water of the eastern ECS since 24, OOOyrs B.P., (1) a stage influenced by coastal water from 24,000 to 16, OOOyrs B.P., (2) a stage also influenced by coastal water and extremely low salinity from 16,000 to lO,OOOyrs B.P., and (3) a stage controlled by the modem open-sea water related to the Kuroshio with both higher temperature and higher salinity since l0,000-8,0OOyrs B.P.
Oxygen isotope records in G.bulloides from the northernmost core KH82-4-14 show that the three planktic foraminiferal faunal phases correspond to the last glacial, deglacial and postglacial stages, respectively. Planktic foraminiferal assemblage during the deglacial stage which is represented by extremely high percentages of G.quinqueloba, is quite different from those during the glacial and postglacial stages, linked to surface water in low salinity. A negative oxygen isotope excursion in G.bulloides during the same period is highly correlated to the 'G.quinqueloba anomaly', also indicating a decrease in surface water salinity. In contrast to core KH82-4-14, the 'G.quinqueloba anomaly' in the two southern cores RN8O-PC3 and B094-20 PN-3 is less remarkable, implying the northernmost ECS was more severely diluted during 16,000-l0, OOOyrs B.P.In cores KH82-4-14 and B094-20 PN-3, sedimentation rates during 20,000-16, OOOyrs BP are as low as those during the period younger than 8,000-6, OOOyrs BP, suggesting a small sediment supply during the LGM.