関東平野中央部における後期更新世以後の古地理の変遷 (関東平野における第四紀後期の環境変化と文化の発達<特集>)

概要

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It is well known that the tectonic basins called the Kanto Tectonic Basin in the central part of the Kanto Plain has been subsiding during the Quaternary Period. Many previous workers have a firm belief that the rivers of Tonegawa and Arakawa had been running along the Tonegawa Lowland situated in the center of the Basin and flowing into Tokyo Bay before their water-courses were changed artificially into the present courses about 300 years ago.The author pictured a paleogeographic map (Fig. 2) about the central part of the Kanto Plain in the Late Pleistocene basing upon the pattern of valleys dissecting the uplands composed of fluvial and coastal deposits during the Middle Pleistocene, and assumed that the rivers of Tonegawa and Arakawa was flowing along the Arakawa Lowland at that time. The same result was already published by MATSUDA (1974) basing on the subsurface data, who figured some geologic sections traversing the Tonegawa, the Nakagawa, and the Arakawa Lowlands.That is to say, the rivers of Tonegawa and Arakawa took their courses along the Arakawa Lowland from the Late Pleistocene till the Early Holocene. On account of the deposition in the floodplain and the subsidence of the Kanto Tectonic Basin, these rivers changed their courses to the east about 4, 000 years ago. Rapid deposition began in the Tonegawa Lowland area and uplands were buried, and some sites of the Middle Jomon stage on the uplands, too.
日本第四紀学会の論文