| Co-Investigator(Kenkyū-buntansha) |
HIRAI Yukihiro Lecturer, Ehime University, 教育学部, 講師 (30181134)
UMITSU MASATOMO Associate professor, Nagoya University, 文学部, 助教授 (50127883)
OHMORI Hiroo Associate professor, University of Tokyo, 理学部, 助教授 (60092160)
ENDO Kunihiko Associate profesor, Nihon University., 文理学部, 助教授 (70059781)
MORIYAMA Akio Professor, Aichi Gakugei University, 教育学部, 教授 (60024006)
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| Research Abstract |
The aim of this study is to make clear the change of the landforms and sediments of the alluvial plains, and the relationship between the late Quaternary environmental change and the formation of the alluvial plains and Recent alluvial sediments (Chuseki-so). Regional characteristics of the formation of alluvial fan, and the relationship between the landform pattern of alluvial plains and river form pattern were studied in Japanese wide. Detail analysis on the landforms of alluvial plains and Recent alluvial sediments using tephrochronology, archaeological data, and several kinds of analysis were performed in the mountains and alluvial lowlands by each investigators. Late Quaternary paleoenvironments were also clarified by investigators using pollen, grain size and diatom analyses. Based on these investigations, several geomorphic periods in the late Quaternary are distinguished in both mountain and coastal area. In the Tanigawa mountain region, several depositional periods were observed after the Last Glacial Muximun. Distinct debris formation period were also recognized in the mountain areas in central Japan. On the other hand, several periods of remarkable deposition were shown in some alluvial lowlands. Such as BG period, HBG period, ca 8,000yBP, 7,000-6,000yBP, 5,000-4,000yBP, 3,000-2,000yBP, ca 1,000yBP in the Nakagawa Low-land of the Kanto Plain, ca 5,000-4,000yBP in the Nobi Plain, midle Holocene in the Matsuyama Plain, and so on. Relatively stable periods are also recognized in each alluvial plain. The absolute age of these active and stable periods in the regions are not coinside mutually in the present investigations. The effect of natural environment as climatic change on the land-forms and sediments are not distinctly clarified yet. Recent alluvial sediments in the Ryukyus are fine and less gravels, and the remarkable sedimentary period is not clear in the region.
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