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[D-1.3.1 Research on Long-term Changes in Biogeochemical Cycles of Elements in the Oceans based on Chemical Components of Marine Sediments]

[Contact Person]

Takejiro Takamatsu
Section Director, Soil Science Section
Water and Soil Environment Division
National Institute for Environmental Studies
Environment Agency
16-2 Onogawa, Tsukuba, Ibaraki 305, Japan
Phone +81-298-50-2469, Fax +81-298-51-4732

[Total Budget for FY1993-1995]

23,100,000 Yen (FY1995 7,789,000 Yen)

[Abstract]

　Sediment cores collected from the shelf of the Weddell Sea(GC808) and from ca. 3500m depths of the Weddell Sea(GC801), the Ross Sea(GC1208) and off the Enderby Land(GC1OO2) in the Antarctic Ocean were analyzed for opal, calcium carbonate, carbon, nitrogen and for 25 major and trace elements by neutron activation analysis. Foraminiferal tests were isolated from calcareous ooze layers of the cores and AMS ¹⁴C ages were determined. As the results, opal contents varied remarkably from <2% in the lower part of Core GC1002 to ca. 45% of Core GC808, which correspond to the average accumulation rates of from ca. 0.6cm/kyr to ca. 200cm/kyr, respectively. Ba contents showed positive correlation relative to opal contents in each core but the slopes were quite different among the four cores. Relationship between opal and Br showed a linear correlation for the four cores. Based on the AMS ¹⁴C ages and opal contents, biological productivity due to diatom increased abruptly at 12 kyr BP in the Weddell Sea. It has been revealed that opal contents as well as Ba and Br contents will become very good proxies of paleoproductivity in the oceans.

[Key Words]

Antarctic Ocean, Sediments, AMS ¹⁴C ages, Productivity, Opal, Trace Elements