Abstract:
Based on many geological data obtained since 1970, the Neogene to early Pleistocene (Eopleistocene) submarine geology of the deep sea area of the Japan Sea are summarized mainly from the chronological, stratigraphical, paleontological and volcanologic point of views. Most of these data were analyzed mainly on the dredge samples from various submarine rises of the Japan Sea except for DSDP site 299, 300, 301 and 302. According to Russian investigations, for instance, diatom fossil assemblages were identified in 115 samples of 74 stations within 216 dredge samples from 124 stations. In reference to the obtained chronological and paleontological results from each sample, stratigraphy, lithological characteristic and paleontological data are separately described as 1) Upper Oligocene-Lower Miocene, 2) Lower to Middle Miocene, 3) Upper Miocene, 4) Pliocene and 5) Eopleistocene, respectively. Soviet explorers began to study the Japan Sea interior in 1970 from the Yamato Rise. At that time, during the 47th cruise of the R/V Vityaz and 6th and 7th cruises of the Pervenets, the first samples of bedrock were recovered, including those dated presumably by the Pliocene (Vasiliev and Markevich, 1973). From 1973, the Pacific Institute of Oceanology had been conducted expeditions, mainly aboard the Pervenets. Since 1981, when economical zones were established, the expeditions were mainly carried out within the economical zones of the USSR and the People's Democratic Republic of Korea. Then, almost all submarine rises, sea-mountains, ridges, banks have been investigated. The results were partly published at different times (Vasiliev et al., 1975; Bersenev et al., 1979; Lelikov et al., 1979; Tsoi et al., 1985) and summarized in "Geology of the Japan Sea Bottom" (1987). The present work makes use of Neogene diatom zonation, modified by Akiba (1986), which permitted a more precise age determination. The present work used the data of dredging obtained in fourteen cruises of the Pervenets and single cruise of the R/V Kallisto and Vityaz, Professor Bogorov and Dm. Mendeleyev (see Catalogue of dredging stations). The areas of underwater rises have numerous landslides; there are less outcrops of Neogene deposits than the continental slope; the regions of seismic profiling have lesser area. Therefore, the interval-by-interval dredging of the Neogene section was performed only on Alpatov Rise; the rest elevations yielded less data. The comparison of geological results with the data of seismic profiling was conducted only on the northern periphery of the Japan Basin (Bezverkhny et al., 1988) and on the East-Korean Rise (Lelikov and Bezverkhny, 1985). Stratigraphic reconstructions are based mainly on the results of diatom analyses. This work presents descriptions of diatom assemblage (by Tsoi), spore-pollen spectra (by Gorovaya) and main rock types (by Vashchenkova and Terekhov). Methods of investigation are already described in Chapter 5-1.2. Diatoms have been studied on 216 samples from 124 stations, but only 115 samples from 74 stations had sufficient