PALEOGEOGRAPHIC EVOLUTION OF THE JAPANESE ISLANDS IN THE NEOGENE

本研究的目的是阐明日本列岛晚第三纪的构造变形及其引起的古地理演化，根据古地磁研究，本州岛的变形主要表现为本州岛西南部的顺时针旋转和东北部的逆时针旋转，它起源于日本海的开放。但是，在日本诸岛的外围地区，如北海道和九州岛等，构造旋转的运动却比本州岛西南和东北地块的旋转运动复杂得多。虽然两年的研究时间似乎太短，不足以阐明日本列岛新近纪如此复杂的构造变形，但整个日本列岛新近纪构造变形的轮廓已变得更加清晰。本研究组一直在发挥IGCP（国际地质对比计划）-246项目日本工作组的作用。作为工作组的一项活动，我们于1992年8月25日在京都举行的国际地质大会（IGC）上举行了一次关于“太平洋和全球新近纪事件（IGCP 246）”的特别会议。会议非常成功，来自世界各地的许多科学家出席了会议。

The aim of the present research is to clarify the tectonic deformation of the Japanese Islands in the Neogene time and to figure out the paleogeographic evolution as consequence of the deformation.Essentially, the deformation of the island was expressed by a rotation of clockwise of the southwestern Honshu Island and that of counter- clockwise of the northeastern part as inferred from paleomagnetic study, which was originated by the opening of the Japan Sea. But the tectonic rotations are found to have undergone more complex movements, for example, at the peripheral parts of the Japanese islands such as the Hokkaido and the Kyushu islands rotated differently from the rotations of the southwestern and the northeastern blocks of the Honshu Island. Although a two-years research project seems to be too short to clarify such a complex tectonic deformation of the Japanese islands in the Neogene, the outline of the tectonic deformation in the Neogene becomes more clear over the whole Japanese islands.Present research group has been playing the role of the Japanese Working Group of IGCP(International Geological Correlation Program)-246 project. As an activity of the Working Group, we had a special session on "Pacific and global Neogene events (IGCP 246)" on 25, August, 1992, at the International Geological Congress (IGC) held in Kyoto. The session was very successful with the attendance of many scientists from the world.