過去64万年間の日本海における深海性放散虫の変遷(<特集>日本海の生物相の変遷と環境変動-過去,現在そして未来へ向けて)

概要

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The assemblage of the recent deep-dwelling radiolarians in the Japan Sea is characterized by the lack of primary deep-water species, which typically occur in the great depths of the world ocean, and by predominance of the secondary deep-water species Actinomma boreale group and Cycladophora davisiana, which usually live in the subsurface or intermediate depths in the high latitude oceans. Such peculiar assemblage was formed with the beginning of active deep-convection in the Japan Sea during the deglacial period. In contrast to this assemblage, during the last glacial maximum, a modem intermediate-water species, Ceratospyris borealis, dominated the radiolarian assemblages and probably had a habitat between low salinity surface water and anoxic deep water. The secondary deep-water species C. davisiana significantly varied in abundance since 640 ka. During the MIS-5 to -3 characterized by millennial scale climatic changes known as the Dansgaad-Oeschegar Cycles, C. davisiana increased frequently at transition periods from interstadial to stadial conditions. Such high abundance of this species might be related to well oxygenated deep waters which were associated with active deep-convection and to a supply of higher organic matter, considering the correlation between the high abundances of the species and the dark laminated layers observed in the studied cores.
日本古生物学会の論文
2007-10-15