The Continental Shelf off San-in District of Japan

Abstract

The continental shelf off San in District of Western Honsyu, Japan, is unusually deeper than ordinary continental shelves around Japanese Islands. The depth of these continental shelf edges range 270-490m off northern Noto Peninsula, 400-500m off west of Noto Peninsula, 500-350m off Wakasa Bay, 400-500m along east side of Oki Submarine Spur, 300-400m along west side of Oki Submarine Spur and 300-400m off Yamaguti Prefecture. The submarine terrace with 130-150m deep of terrace edge is found on the surface of the deep continental shelves above mentioned, which are composed of thick sedimentary layers intercalating several unconformities. The basal uncon- formity of these sediments is correlated to Upper Pliocene to Lower Pleistocene. Since this unconformity, the continental shelf off San-in District has become the area of subsiding crustal movement and continuous deposition of thick sedimentary series in which several unconformities might be caused by Quaternary glacial sea level lowerings are found. The deep drilling of the area and analyses of sedimentary fades of samples are desired from the view point of the glacial sea level ocsillation history.