The Hamaishidake Group (Pliocene) is divided into three formations, that is, Sattatoge, Nakagouchi and Kawaino Formations in ascending order. The group consists of conglomerate, alternations of sandstone and mudstone, mudstones, volcanic conglomerate formed by submarine volcanic mud flow, basaltic to andesitic subaqueous lavas and pyroclastic rocks. This group is believed to be deposited in a submarine trough of bathyal environment. The Ihara Group (Early to Middle Pleistocene) is distributed around the lower reaches of Fuji River. The Ihara Group is divided into two formations, namely, Kambara Formation composed of conglomerates and Iwabuchi Formation composed of conglomerate and volcanic rocks, in ascending order. Volcanic rocks of the Iwabuchi Formation are basalt to andesite lava, tuff breccia, dacitic lava dome and basaltic dykes. The Ihara Group is believed to be deposited in shallow environments such as continental shelf, lagoon and/or delta. Basalts and andesites of the Sattatouge Formation show tholeiitic petrochemical characters. Basalts of Nakagochi Formation are tholeiitic, but andesites and dacites are calcalkaline. Basaltic lavas and dykes of the Iwabuchi Formation are tholeiitic, and andesitic lava and dacitic lava domes are calcalkaline. Based on TiO_2-FeO/MgO, TiO_2-MnO-P_2O_5 diagrams and patterns in the N-MORB-normalized diagram, the Hamaishidake Group and Ihara Group belong to island-arc tholeiite type. Early to middle Miocene volcanism in the western part of South Fossa Magna is back-arc type tholeiite and oceanic island alkali basalt erupted in deep sea. Quaternary volcansim on the Izu-Ogasawara arc is island-arc tholeiite and calcalkali andesites type, and formed stratovolcanos. Volcanism of the Hamaishidake and Ihara Groups took place in the transitional stage between the Early to Middle Miocene back-arc volcanic setting in the proto-Izu-Ogasawara arc and the Quaternary volcanism on the Izu-Ogasawara arc. This transitional volcanism seems to be related with collision of the Tanzawa and Izu Massifs.

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The Japanese members of dytiscid beetles (Coleoptera: Dytiscidae) are known by about 100 species, which live in freshwater environments. The fossils are also common in Quaternary deposits. The dorsal mesh-like microsculpture is visible in head, pronotum, elytron etc. It may be very useful in identifying the fossil specimens. Although their paleoenviromental and paleoclimatic studies have been carried out, diagnostic feature of the microsculpture has not been used. I made impressions of the microsculpture of dried living specimens using the polyvinyl acetate emulsion (so-called "Wood Glue"). Dorsal microsculpture of 24 species of six genera in Dytiscidae: Platambus, Agabus, Ilybius, Rhantus, Hydaticus and Cybister, were compared under a light microscope. Most species possessed diagnostic features of elytral microsuclpture, though some taxa (e. g. several species of the genera Agabus and Hydaticus) could not be distinguished from each other by them. Some use of dorsal microsculptures in these taxa for the fossil identification were applicated and the possibility for general use were discussed.

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Stratigraphic distribution of Japanese Quaternary proboscidean species is reviewed on the basis of tephrostratigraphy and oxygen isotope stratigraphy. The appearance and disappearance of the proboscideans in the stratigraphic sequences are as follows: Mammuthus shigensis appeared at the oxygen isotope stage 35 (1.15Ma) and disappeared at the stage 15.5 (0.62Ma); Stegodon orientalis appeared at the stage 15.5 (0.62Ma) and disappeared at the stage 15.1 (0.57Ma); Palaeoloxodon naumanni appeared at the stage 10 (0.36-0.34Ma). This paper estimated the immigration age of S. orientalis and P. naumanni into the Japanese Islands, and the age of the land bridge formation between the Japanese Islands and the adjacent Asian Continent, based on the environmental changes of the Japan Sea during the middle Quaternary which were obtained by the analyses of ODP cores. We concluded that S. orientalis and P. naumanni immigrated into the Japanese Islands at the stage 16 (0.63Ma) and the stage 12 (0.43Ma), respectively.

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A 584.5cm-long core sample (89TB4) was collected from the 3400m deep depression located between the Kaiyo Seamount and the Vityaz Seamount in the northern Japan Sea. Sedimentological and micropaleontological study was carried out for the core. Based upon these examinations, the core sample was divided into three units; lower, middle and upper units, respectively. The lower unit is characterized by alternation of dark-colored laminated mud and light-colored massive mud. Three volcanic ash layers are intercaleted in the core. The middle unit is characterized by dark-colored liminated mud, gypsum crystals and arctic water foraminifera, indicating stagnant bottom water condition and very cold climate. This stagnant and cold climate stage may be correlated to the the last glacial maximun. The upper unit is composed of massive mud intercalated with thin sand layers which might be deposited from trubidity currents. This part indicates that convection of sea water began again and temperature of the surface water increased after the last ice age.

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The Echigoyuzawa area is located in between the Nanatani area of Niigata Prefecture and the Takasaki area of Gumma Prefecture, where the Miocene biostratigraphic zonations were established. The Miocene strata in the Echigoyuzawa area are divided into the Uwano, Ohsawa, Mugurazawa Formations in ascending order. The Uwano and Mugurazawa Formations yield many planktonic and benthic foraminiferal fossils. The planktonic foraminiferal zone of the lower Uwano Formation is correlated to the Globorotalia peripheroronda-Globorotalia quinifalcata and Globorotalia pheripheroacuta-Globorotalia miozea (s.1.) zones by Maiya (1978). The latter foraminiferal zone is also found in the upper Mugurazawa Formation. The occurrence of Orbulina universa and the first appearance of Grt. pheripheroacuta in the Uwano Formation, and the coexistence of Grt. pheripheroacuta and Grt. cf. miozea conoidea in the Mugurazawa Formation indicate Early Middle Miocene in age. The benthic foraminiferal assemblages from the Uwano Formation and the upper part of the Mugurazawa Formation are characterized by the abundant occurrences of Nonionellina labradorica and Uvigerina proboscidea. These species are distributed in the upper middle bathyal zone in the modern Pacific Ocean. Many individuals of Haplophragmoides sp. and Dorothia sp. which were abundant in the lower middle bathyal zone during the Miocene, occur in the lower Mugurazawa Formation. Thus, the Uwano and the upper Mugurazawa Formations were deposited in the upper middle bathyal zone. The paleobathymetry of the lower Mugurazawa Formation is estimated to be the lower middle bathyal zone.

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