石灰質ナンノ化石群集からみた北極海および北半球中-高緯度海域の後期鮮新世寒冷化(<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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I reconstruct the late Pliocene to Quaternary paleoceanography of the north Pacific, Arctic, and north Atlantic Ocean based on geographical distribution of cold water nannofossil Coccolithus pelagicus (Wallich) Schiller. Since the species drastically increased at 2.75 Ma in the Arctic Ocean and high latitude regions of western marginal sea of both Pacific and Atlantic Oceans, it decreased at the central to eastern north Atlantic Ocean at 2.9-2.8 Ma just before 2.75 Ma event. This indicates that strengthening of north Atlantic thermohaline circulation just before 2.75 Ma induced an intensified moisture supply to northern high latitude, and resulted in drastically increase of Northern Hemisphere glaciation at 2.75 Ma. Although the abundance of C. pelagicus in the central to eastern north Atlantic Ocean is low until 2.38 Ma, it suddenly increased just after the time. The same characteristics are also found in the middle latitude region of eastern Pacific Ocean at that time. These results indicate that the influence of the late Pliocene glaciation increased in two steps at 2.75 Ma and 2.38 Ma in the Northern Hemisphere.
2007-10-15