東海地方の沖積海岸平野とその形成過程

概要

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Alluvial plains on the coast of the Tokai region can be classified into two types of deltaic fans and deltas. The former extends on lower drainages of large rivers which are carving steep hinter mountains of the region and flowing abruptly into the sea without middle courses, and the latter is formed on lower courses of small rivers or lateral side areas of deltaic fans. Deposits of deltaic fan type plains consist largely of fluvial gravels owing to plentiful supply of materials from the mountains, those of deltas are, however, composed mainly of marine or estuarine silt. From the view point of the geology of terrace deposits of the region, the shift of locations of lower drainages of the present large rivers since middle Pleistocene is closely related to the Quaternary undulatory movement of the region. Most of alluvial coastal plains of the region has been formed in areas of down-warping since the latest geological ages. As an example of alluvial plains of the region, stratigraphy and geologic history of the lower drainage of Kano River, north of the Izu Peninsula, is presented mainly by means of fossil diatom flora which were obtained from a boring core of 44m long in a central part of the area. Two sedimentary cycles which represent marine invasions are recognized in the area.
日本地質学会の論文
1972-12-25