摘要
Quantitative analyses have been carried out on radiolarians from 65 samples of Core 255 in the southern Okinawa Trough. The distribution of taxa and the results of Q-mode factor analysis show that during the last 20 000 years three radiolarian assemblages could be distinguished which can be correlated to high and low productivity levels indicated by the organic carbon content, radiolarian abundance and ratio of Nassellaria/Spumellaria in the sediment. TheTetrapyle quadriloba assemblage of thr last glaciation and deglaciation is associated with high productivity whereas the early HolocenePolysolenia spinosa and the middle and late HoloceneCarposhaera globosa assemblages correspond to low surface productivity. Meanwhile, the variations in the ratio of radiolarian fragments indicate higher SiO2 dissolution during the Holocene than during the last glacial stage.
Quantitative analyses have been carried out on radiolarians from 65 samples of Core 255 in the southern Okinawa Trough. The distribution of taxa and the results of Q mode factor analysis show that during the last 20 000 years three radiolarian assemblages could be distinguished which can be correlated to high and low productivity levels indicated by the organic carbon content, radiolarian abundance and ratio of Nassellaria/Spumellaria in the sediment. The Tetrapyle quadriloba assemblage of the last glaciation and deglaciation is associated with high productivity whereas the early Holocene Polysolenia spinosa and the middle and late Holocene Carposhaera globosa assemblages correspond to low surface productivity. Meanwhile, the variations in the ratio of radiolarian fragments indicate higher SiO 2 dissolution during the Holocene than during the last glacial stage.
