The geological data on regions surrounding the deep-sea basins of the Japan Sea suggest that geosynclinal systems were emplaced as ensimatic geosynclines in Early Paleozoic and Precambrian times. Thus, the general crustal structure of this region has been developing from this time as a result of the irreversible geosynclinal processess of crustal formation. The deep-sea basins represent relict geosynclinal basins, probably of Early Mesozoic age and are generally characterized by pelagic clay sedimentation before the Neogene and intensive turbidite sedimentation from Miocene till Recent times. Turbidite sediments fill the northern part of the huge Tatar Strait Trough in the north and Tsushima Basin in the south. The stable geosynclinal condition from the Early Mesozoic and perhaps (if we bear in mind the compaction of the transparent layer pelagic clay) from the Paleozoic in the Japan Sea area is in contradiction with (Hilde and Wageman, 1973) Late Mesozoic or Early Tertiary rifting and subsequent sea-floor spreading for this region.