砂丘形成期分類のためのインデックス

抄録

Many coastal sand dunes are distributed along the present strand-line of Japan. The ages of formations of those sand dunes can be classified into three types, as the Pleistocene sand dunes, “Older”and“Younger”Dunes in Holocene.
The Older Dunes in Holocene were formed during the stage of the highest sea level in the Flandrian transgression, which was about 3 meters above present mean, the period of which ranged from 6, 000 to 4, 500B.P.
Between approximately 3, 500 and 2, 000B.P. the sea level should have dropped about 2 or 3 meters below the present level. As a result of the regression the coastal dune (“Lost Sand Dune”) developed in off the coast of Hokuriku district, and the back marshy land was covered by the peat layer and forest which are found from the bottom of the sea present time. The peat layer continues to the humic sand layer on the top of the Older Dune. We can see these humic sand layers, which is contained archaeological remains in about 3, 500-1, 500B.P., on the Older Dunes in various places of Japan.
Following about 1, 500B.P., the sea level seems to have risen briefly to a level slightly above present datum. The Young Dunes were formed along the newly submerged coastlines and overlaid the humic sand layers on the Old Dunes.