| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
It is important how to draw out the oceanic condition of the fossil assemblage to reconstruct the paleooceanographical environment. The coccolithophorid assemblages change according to the seasonal change is clarified by using the sediment trap samples. The assemblages transition by the deposition process is clarified. In addition, it aimed to analyze the coccolith thanatocoenoses in the surface sediment is analyzed in the trap location, and to clarify the relation among the assemblages seasonal change, the vertical transport process, and the dissolution process.
It became clear the following from the sediment trap experimentation result of mooring at depth 1371m and 4787m in northwest Pacific Ocean. It has been understood that the dominant three species, Emiliania huxleyi, Gephyrocapsa oceanica and Florisphaera profunda, from the analysis of the trap during year in this sea area are leveled assemblages. Therefore, it turned out that expecting the environment of the annual mean of surfa
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ce water would be reflected was appropriate in the environmental analysis with these taxa in the surface sediment in this sea area. On the other hand, because Coccolithus pelagicus was recognized increasing from April to May in the trap, it turned out that this species in the surface sediment indicated the period when the biological production from April-June was high.
Increase of Oolithotus fragilis had been confirmed the increasing nutrients periods from the trap experiment. Detailed environmental transition analysis was done about the relation between the seasonal variation of the deposition process of the coccolithophorid and the surface sediment assemblages in the equator Pacific Ocean during past 250,000 years. The increase in the production frequency of this species was recorded in the oxygen stages 1, 3, 5, and 5/6 boundary. This species of increase periods were suggested to be a result of reflecting the influence in winter more strongly in this sediment core, because this species of increase season by the trap experiment has been limited in winter.
The characteristic of the proxy taxa became clear different in each region and the paleooceanographical environmental variation's detailed analysis was enabled based on the result of the depositional processes and the considering of the characteristic coccolithophorid assemblages with the seasonal change. Less
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