沖積世低位海水準
スポンサーリンク
概要
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There is disagreement concerning sea level changes during the past 7000 years. SHEPARD and CURRAY (1967) take the view that sea level stood -69 m. lower 7000 years ago than at present, and that during this period it has risen gradually to attain the present sea level. Otherwise, FAIRBRIDGE (1961) believes there is evidence that the sea rose to higher levels during the past 6000 years, and that there have been three brief stillstands 3, 1.5 and 0.5 m. above the present sea level within this period. In Japan, the maximum sea level during the postglacial age was suggested to lie at 6 m. above the present sea level in the early Jomonian age. Fujii and FUJI (1967) believe there is a phase of lower sea level between 3000 and 1500 years ago than present sea level as proved by the submerged forests.<BR>The author studied rocky micro-topographies in the shallow sea bottom to obtain any evidence concerning lowered sea levels during the Holocene age.<BR>Submerged spur during the Holocene transgression may be better places to solve the above question. He took the method of projections of the overall depth points along the submarin spurs of the south coast of Shima Peninsula, the west coast of Shimonoseki City, the coast of Ena Harbour, Fukushima Prefecture and the coast of Cape Isone, Chiba Prefecture. In spite of the spurs dissected by grooves, summit level show 4 levels of about -2 m., -35 m., -68 m. and -912 m. with each similar depths. Some of spurs has the recognizables on the summit at each levels, as Hirose and Watari submarin spurs.<BR>About -2 m. plane may be abrasion platform related to the present sea level as pointed out by late Dr. MII (1962). Other three planes are abrasion platform related to the ancient sea levels. It is thought that there may be a possibility that those three levels lower than the present sea level are closely related to the fluctuation of sea level during the past 6000 years.
- 社団法人 東京地学協会の論文