In recent years, there have developed some studies on sea-level changes during the Late Holocene in Japan. When reviewed in detail, however, the results of those studies are found consisting of two cases; one case for a curve-drawing in favor of the Fairbridge curve, and the other for that in favor of the Shepard curve by making different assumptions about the process of crustal movements. This is also true even when the same area is chosen as an objective of those studies. This shows that in Japan where crustal movements have been great, studies about crustal movements themselves must be important in order to investigate ecstatic sea-level changes.
Nevertheless, there are in them some common points concerning the height of the past sea-level changes. One is that the sea-level changs at the last glaciation maximum (about 18, 000 B. P.) are thought to have ben about 140 meters below the present sea-level, judging from the depth of the bottom in some buried valleys which can be found throughout Japan. Another is that, judging from the depth of th bottom in marine silt and clay beds that were accumulated in time of the Flandrian transgression, the sea level at the earliest period of the Holocene is supposed to have been about 40 meters below the present sea level.
As studis about the recent alluvial formation proceed, there have lately emerged some researchers who insist on sea-level changes in favor of the Shepard curve, while most of the researchers in Japan have reported that the sea level was higher around 6, 000 B. P. than at the present. Although some studies have reported that the sea level fell temporarily and rose again later in some areas, there would be little possibility that the fluctuation was caused by glacial eustasy. It is because it would be almost impossible to assume that the expansion of an ice sheet made the sea level lower at a rate of over 0.1 meter per century. Apart from such fluctuations, traces can be found throughout Japan which indicate that the sea level was two to three meters lower around 2, 000 B. P. than now.
It would seem to me that future studies in Japan about the sea level, first of all, should consist of finding out regional characteristics of curves for sea-level changes on the continental scale, by eliminating as much influence as possible caused by crustal movements or orogenic movements limited to a comparatively narrow area. It would not be possible, I assume, to investigate eustatic and absolute sea-level changes until we are through with those problems discussed above.