最終氷期以降の日本沿岸域の風成堆積層
海水準との関連について
1982 年 21 巻 3 号 p. 223-227
詳細
1982 年 21 巻 3 号 p. 223-227
The eolian sand members along the coast of the Japan represent at least five major periods of accumulation. These deposits include well-defined paleosols which divide individual eolian sand members into five parts. The five major periods of eolian sand accumulation can be found as follows: 4, 000-5, 000y.B.P. (the youngest); 18, 000-20, 000y.B.P.; 30, 000y.B.P.; 50, 000y.B.P.; and 70, 000y.B.P. (the oldest). Among these eolian sand members, members of 70, 000y.B.P., 50, 000y.B.P., and 4, 000-5, 000y.B.P. cover a wide area. These periods of accumulation are correlated with the early stage of regression phase during the period of the Last Glacial Age and Holocene. On the other hand, the distribution patterns of eolian sand members of 30, 000 and 18, 000-20, 000y.B.P, are limited in a few coastal areas. As coast lines in two periods were located more than 50km apart from the present coast line, sand could not be transported by the prevailing wind to the position of the present coast line. Two sand members are reaccumulation deposits which stem from older eolian sand members. Loess which comes from China had deposited on the upland in Kyushu and Ryukyu Islands. Loess had been much mixed in the paleosols during the Last Glacial Age. The accumulation ratio of loess is estimated 2.1-3.3g/cm2/1, 000 years in Kyushu.
