Migration of Kuroshio Front and Paleoenvironment during the late Quaternary

本研究的目的是从黑潮锋迁移的角度重建西北太平洋晚第四纪以来的古环境变化，并通过有孔虫测试的微化石组合和氧碳同位素来识别。在苏加鲁湾、博苏半岛和鹿儿岛附近海域采集了四个海相岩心。对岩心进行了详细的分析，包括微型浮游动物、硅藻、放射虫和有孔虫的微化石组合，以及有孔虫测试的氧-碳同位素。结果表明，黑潮锋面的波动特征如下：1.黑潮锋面于公元前14000年到达苏鲁加湾附近。在公元前12000到10000年间，锋面撤退到苏加鲁湾附近的西南部地区。锋面在公元前10000年穿过包苏半岛附近的地区。锋面在公元前7,000到5,000年间到达鹿岛附近。本文还对包索半岛日本海沟8800m水深的沉积物圈闭样品中硅藻和浮游有孔虫的分布进行了重要的基础性研究。

The objective of this study is to reconstruct the paleoenvironmental change of the northwestern Pacific Ocean since the late Quaternary in terms of the migration of the Kuroshio front which is discriminated by the microfossil assemblages and oxygen-carbon isotopes of foraminiferal test. Four marine cores were collected from off the Sugaru Bay, Bousou Peninsula, and Kashima-NAda. The detailed analyses of the cores were performed on microfossil assemblages of nannoplankton, diatoms, radiolarians, and foraminifera, as well as oxygen-carbon isotopes of foraminiferal tests. Consequently, it was revealed that the Kuroshio front had fluctuated as follows:1. The Kuroshio front reached near the region off the Suruga Bay at 14,000 years B.P.2. The front retreated to the southwestern region off the Sugaru Bay between 12,000 and 10,000 years B.P.3. The front passed through the region off the Bousou Peninsula at 10,000 years B.P.4. The front reached near the region off the Kashima-nada between 7,000 and 5,000 years B.P.5. The same oceanographic condition as the present one was established after 5,000 years B.P.In the present study, an important and fundamental study was also carried out concerning the distribution of diatoms and planktonic foraminifera in the sediment trap samples which was recovered from water depth of 8,800 m at the Japan Trench off the Bousou Peninsula.