第四紀後期の海洋環境と生物生産 縁海の古海洋学 縁海の海洋環境変遷とその重要性

Abstract

Marginal seas, such are located as Bering Sea, Okhotsk Sea, Japan Sea, East China Sea, South China Sea and Indonesian seas, locate along the western rim of the Pacific. They have only a small area but are regions of high biological productivity, and thus expected to play an important role on global environment. Each of them has an unique characteristics on bathymetry, water exchange between the adjacent marginal seas and/or open ocean, primary productivity and volumes of fresh water input and terrigeneous material supply. Because they connect each other and to the open ocean through the shallow straits, characteristics of water masses flowed into the marginal seas were highly influenced by global sea level fluctuations. Furthermore, climatic change affected the volume of terrigenous supply to the seas. Therefore, paleoenvironments of the marginal seas largely changed with long-term sea level changes and short-term climatic changes. Recent studies on paleoceanography of the Japan Sea and the South China Sea suggest the importance of Asian monsoon to control the oceanic environments of the marginal seas. Hemipelagic sediments with higher sedimentation rates in the marginal seas recorded paleoceanographic changes in high resolution. Multidisciplinary studies for large-diameter long piston cores from the East Asian marginal seas may provide good information for global climate changes in the late Quaternary.