1990 年 29 巻 3 号 p. 267-275
The existence of a land bridge in Tsugaru Strait, Northeast Japan, is hypothesized with reference to caldron-saddle topography and submarine terraces in the western part of the strait and to late Pleistocene marine terrace deformation on land. It is possible that the Tsugaru Land Bridge was formed after the lowest submarine terrace (Terrace VII) and, before the paired caldrons. If the land bridge existed in the last glacial maximum stage, 18 to 20ka ago, the sea level is estimated to have fallen below the depth of 130 meters. However, Terrace VII has not been age-determined yet. Tectonic movement, deduced from marine terrace deformation on land is not detected from height changes in continental shelves, caldrons, and saddle features. Differential movement is also not found in the height distribution of submarine terraces, at least in the Tappi Saddle. Much data on subsurface geology and structure beneath continental shelves are necessary in order to know the age of the Tsugaru Land Bridge.