Abstract
The Dewa Bank Chain, located on the outer edge of the continental shelf offshore Akita, consists of banks and knolls tending north-south over about 100 km. In this chain, Shinguri Bank is topped by an obvious flat area that is thought to be mainly an abrasion platform that formed during the eustatic lowstand of the last glacial period. Based on three-dimensional seismic interpretation, depth of the platform ranges from 150 to 160 m at the deepest. However, the Last Glacial Maiximum（LGM）lasted until 20.5 Ka and the eustatic sea level at that time was 125~130 m lower than at present. Therefore, the abrasion platform of Shinguri Bank at the LGM is 10~25 m deeper at present than the sea level of the LGM. This suggests that the Shinguri Bank has subsided at an average of 0.49~1.22 m/kyr since 20.5 Ka. This rapid subsidence contrasts with the uplift tendency of the Oga Peninsula and differs from other knolls and banks in the Dewa Bank Chain, meriting an examination for the development history of the Quaternary tectonics and the influence of post LGM hydro-isostasy at the eastern coast of Sea of Japan.
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