深海底たい積物の微化石層序と地磁気層序

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  • Micro-biostratigraphy and Magnetostratigraphy of Deep-sea Sediments
  • シンカイテイ タイセキブツ ノ ビ カセキ ソウジョ ト チジキ ソウジョ

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This article outlines the present status of micropaleontology of Quaternary deep-sea sediments of the Pacific in relation to magnetostratigraphy. The occurrance of five groups of planktonic microfossils-foraminifera, calcareous nannofossils, radiolaria, silicoflagellates, and diatoms-has been compared with the geomagnetic polarity record of North Pacific deep-sea sediment cores. The relationship between the first and last appearances of characteristic fossils as well as changes in coiling direction of some planktonic foraminifera and the paleomagnetic reversals has been especially examined.<br>Within the geographic limitations for extending the isochronous surfaces represented by the biologic events, regional sequences have been established. Magnetostratigraphy has allowed the correlation of the land-based Oga and Choshi sections with the oceanic sections. The composite scheme, which has 27 micropaleontologic events during the last 1.8m.y. in the North Pacific, will be useful in the interpretation of local magnetostratigraphic and biostratigraphie intervals.<br>Fluctuation of surface temperatures due to Pleistocene glaciation and interglaciation may be a global phenomenon. Attempts to reconstruct paleoclimates from Pleistocene deep-sea sediments of the Pacific have been based upon various data sources-percent carbonate, diatom flora, foraminiferal fauna, oxygene isotopic ratios. In the Northern Hemisphere the paleontologic evidence suggests cooling commenced near the Jaramillo Event and that the Brunhes Normal Polarity Epoch is characterized by longer cold intervals than in the preceding epochs. Marked interglacial events occurred at about 500, 000 and 120, 000 years ago. The subarctic boundary of the Northern Pacific does not appear to have moved more than 6 degrees in latitude during the Quaternary.

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  • 第四紀研究

    第四紀研究 16 (3), 117-128, 1977

    日本第四紀学会

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