Abstract
Surveys made by the surveying ship Soyo-mare of the Imperial Fisheries Experimental Station along the Pacific coast of western Japan revealed nineteen exposures of sedimentary rocks off Sikoku and two in the Osumi Strait. Of these exposures, thirteen off Sikoku and one off Osumi Strait were found to bear marine fossil mollusca and crustacea. The geological age of the strata whence the sedimentary rocks were procured is either Neogene Tertiary or younger. Although Sôyô-maru station 295 in the Osumi Strait is very deep, a littoral facies deposition was found on the basement rock which is tuff. A dissected drowned valley is supposed to exist along the coast of Sikoku. The majority of dredgings made by the Soyo-maru were on the contiental shelf; only a few were made on the continental slope, therefore the presence of Neogene or younger strata on the continental shelf and the existence of a drowned valley, all pnint to recent land submergence in the region in question.
