四国沖から採取された2本のIMAGESコアを用いた第四紀後期におけるテフラ層序(<特集>西太平洋におけるIMAGESコアを用いた高時間解像度の環境復元)

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Tephrostratigraphy is very useful tool to reconstruct the past time framework for marine sediment cores. Northwestern Pacific has many widespread tephras that can serve as time markers, because many volcanoes in the region had repeated large eruptions from the middle Pleistocene to the Holocene. Two IMAGES cores MD012422 and MD012423 were collected from the lower part of continental slope basin off Shikoku and from the central Tosa Basin, respectively. Here we report that the lithostratigraphy, age model, and tephrostratigraphy of these cores. Upper 14 m part of core MD012422 was affected by a significant mechanical extension, which was inferred from the magnetic fabric analyses. Six tephra layers are described in core MD012422 and MD012423. Holocene tephras of two cores are correlated to the Kikai-Akahoya (K-Ah) tephra from the Kikai Caldera on the southern Kyushu, and the Aira-Tn (AT) tephra from Aira Caldera was also obtained in core MD012422. The eruption age of AT tephra was estimated to be 28.1-28.3 cal kyr based on AMS ^<14>C dating of planktonic foraminifera. A tephra layer, which is located at near MIS 4/5 boundary in MD012422, is correlated to the Aira-Iwato (A-Iw) tephra, based on the refractive indices of volcanic glass shards, orthopyroxene, and hornblende. A tephra layer, which is corresponded to the late MIS 5.5, is correlated to the Aira-Fukuyama (A-Fk) tephra. Ata-Toihama (Ata-Th) tephra was also identified in the MIS 8.1 section of core MDO12422. Kakuto (Kkt) tephra was also identified in the MIS 9.2 of core MD012422. The relationship between these tephra layers and oxygen isotopic stratigraphy is important for discussing the revised tephrochronology and distribution of widespread tephras during the middle to late Pleistocene.
2006-03-28

四国沖から採取された2本のIMAGESコアを用いた第四紀後期におけるテフラ層序(<特集>西太平洋におけるIMAGESコアを用いた高時間解像度の環境復元)

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