JpGU-AGU Joint Meeting 2017

講演情報

[EE] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS06] [EE] アジア・モンスーンの進化と変動、新生代寒冷化との関係

2017年5月23日(火) 10:45 〜 12:15 ポスター会場 (国際展示場 7ホール)

コンビーナ:多田 隆治(東京大学大学院理学系研究科地球惑星科学専攻)、Christian Betzler(University of Hamburg)、Peter Dominic Clift(Louisiana State University)

[MIS06-P03] Latitudinal changes of radiolarian assemblage in the Japan Sea during Pliocene to Pleistocene

*板木 拓也1新野 薫2本山 功2松崎 賢史4上栗 伸一3 (1.産業技術総合研究所、2.山形大学、3.茨城大学、4.東京大学)

The Japan Sea (3,700 m maximum water depth) is a marginal sea of the northwestern Pacific, connected to adjacent marginal seas and the Pacific Ocean through four shallow straits (sill depth<130 m). The only inflow of oceanic water is derived from the Tsushima Warm Current (TWC), which enters the Japan Sea through the Tsushima Strait (130 m in depth) in the south.

Radiolarians are one group of the planktic Protista distributed in the world oceans and their fossil records are widely used as a proxy for paleoceanographic study. In the summer 2013, IODP Exp. 346 drilled seven sites in the Japan Sea and two sites in northern part of the East China Sea. We have analyzed radiolarian fossils for all these sites. In this study, geographic distributions of radiolarian assemblage in the Japan Sea during Pliocene to Pleistocene are discussed, such as their relation to global climatic changes and topographic changes with local/regional tectonics.

Significant variations of the well-preserved radiolarian assemblage recorded in the drill sites imply unique oceanic circulation changes in this sea through the examined period. The radiolarian species such as Dictyocoryne spp. and Tetrapyle spp., which characterize the TWC water occurred commonly during interglacial periods since 1.7 Ma suggesting a beginning of warm water inflow from the southern strait. Relative abundance of these subtropical radiolarians tends to be much higher at the southern sites than at northern sites, related to the relative contribution of the TWC. On the other hand, during the Pliocene period, minor influence of subtropical water was only recognized at the southern site suggesting influence of the TWC restricted to the southern coastal area.