浮遊性有孔虫群集から見た鹿島沖の過去14.4万年間の環境変動

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We reconstructed the oceanographic changes during the last 144 kyr off Kashima, central Japan, utilizing several planktonic foraminiferal species extracted from an IMAGES sediment core of 45.82m long (MD01-2421; 36°02'N latitude and 141°47'E longitude; water depth=2,224m). We proposed the results based on the temporal variation in Tf values, (ratio of warm water species)/(warm+cold water species), relative abundance of Neogloboquadrina pachyderma (Ehrenberg) (sinistral coiling), sea surface temperatures (SST) and the faunal similarity between the present core and the surface sediments along the Pacific side off the Japanese Islands together. These results suggest that the core site has experienced under the water mass condition similar to the present Oyashio Current off southeast Hokkaido (42-43°N) during the glacial maxima and the water mass similar to the present Kuroshio Current off south Kyushu to south coast of the Japanese Islands (31-33°N) during the interglacial maxima. The SST estimates at the core site using regional and global transfer functions indicate that the SSTs were lower by〜10℃ around the Last Glacial Maximum (LGM, in particular 19-18 ka) and Marine Isotope Stage (MIS) 6 maximum (135-129 ka) compared to the modern temperature, while the SSTs were higher by〜1℃ during mid-Holocene (8-7 ka) and at MIS 5a (77-76ka), MIS 5c (〜94 ka), MIS 5d (112-107 ka) and MIS 5e (122-119 ka). Most prominent changes off Kashima have occurred during the cold to warm transitions of MIS 6/5 and MIS 2/1, when the Oyashio Current occupied over the core site as well as during the LGM. However, the influence of the Kuroshio Current was more distinct during most of the last interglacial period (MIS-5) than today except short periods of MIS 5b (〜86 ka) and MIS 5d (〜115 ka).
日本古生物学会の論文
2006-03-28

浮遊性有孔虫群集から見た鹿島沖の過去14.4万年間の環境変動

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