A biometrical study on coccoliths of the genus Gephyrocapsa from the Setana Formation, southwestern Hokkaido, was carried out by using SEM and TEM micrographs. The ratio between placolith-length and -breadth is uniform, and the number of shield-elements varies with the size of placolith, thus these cannot be taken as useful characters in distinguishing species of Gephyrocapsa. Three morphological groups are distinguished, though imperfectly, within forms with un-differentiated shield-elements, in terms of placolith-size, bridge-angle and relative pore width. However these three groups do not correspond to the known categories of Gephyrocapsa species. Gephyrocapsa protohuxleyi group (together with G. ericsonii-G. protohuxleyi transitional type) with differentiated shield-elements show similar range of continuous variation with the above mentioned three groups, and it cannot be morphologically separated. It is quite probable that the all forms of Gephyrocapsa from the Setana Formation are in fact specifically unseparable, even though they reveal considerable but morphological variation.

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Itamuro spa is located on southwest foot of Nasu volcano, Central Japan. And the surroundings consist mainly of tuff, tuff breccia and rhyolite belonging to Fukuwata formation of tertiary age. There are 20 spring wells in the spa, drilled 85-890 m deep, and 15 wells marks temperature ranging 22.4-50.1℃, 10 wells issue thermal water naturally 58.3-711.9 l/min and from 5 wells 68.8-400 l/min of the water is pumped up. Among 14 wells, those issuing water is examined chemically, 12 wells issue thermal water of Na・Ca-SO4 type, one well of Na・Ca-Cl-SO4 type and one well of groundwater type. From hydrogeological investigation, the followings are clarified: (1) Dominative discharge area of the water situates about 350 m downstream from junction of Nakagawa river and Yukawa river. (2) Vertical and horizontal distribution of the main chemical components of thermal water can be explained by thermal water flow system. (3) Two chemical types of the water above mentioned are bounded by a fault, running N-S direction and inferred impermeable layer. (4) Geologically and chemically, close correlation between Itamuro and Nasu spas is denied.

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The authors previously reported the Quaternary stratigraphy of the northern part of the Uonuma hills (MASAI and TAKAHAMA, 1981). In the present paper, the authors described the geological structures and investigated the tectonic movement of this area, which are summarized as follows; 1. The surveyed region can be subdivided into three tectonic domains, namely I-the folded area, the Uonuma sedimentary basin proper, II-the stable area, least subsiding part of the basin and III-the fractured area along the Shibata-Koide tectonic line, especially the Aburuma-gawa fault angle basin. 2. The Uonuma sedimentary basin was generated when the basal unconformity of the Uonuma group was formed and developed at the early Pleistocene due to great subsidence with deposition of thick sediments of the middle member of the Uonuma group. The sub-siding center of the (Uonuma sedimentary) basin might have migrated to the north at the stage before sedimentation of the upper member of the Uonuma group, inferred from the marginal unconformity, facies change from middle to upper member and isopach map (MIYASHITA et al., 1972) of the Uonuma group. This change was caused by local upheaval movement. The basin up to this stage is called the "Uonuma sedimentary basin in a narrow sense." The basin was completely disappeared in the middle Pleistocene owing to the rapid regional upheaval movement. The whole basin from the Pliocene to the middle Pleistocene is called the "Uonuma sedimentary basin in a broad sense." 3. The Shibata-Koide tectonic line, the eastern marginal tectonic boundary zone of the Niigata Cenozoic sedimentary basin, was developed by large-scale faulting accompanied with volcanic activity at the end of Miocene epoch. It was still active at the Pliocene and early Pleistocene, and acted to bound the eastern margin of the Uonuma sedimentary basin in the southern part. 4. Faulting, folding and volcanic activity was active in the middle Pleistocene. The Aburuma-gawa fault angle basin along the river Aburuma was formed in the terrace-forming stage by the upheaval movement which also affected to deform the terrace II surface at the northern part of the tectonic zone I.

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The Triassic Inai Group in the Toyoma area, is divided into the following four formations in ascending order as in the type area. The Hiraiso Formation consists of a thick conglomerate and sandstone in the lower part, and an alternation of calcareous sandstone and mudstone in the upper part. Along the western margin of the area, the basal part of the formation is intercalated with thick bed of reddish-purple tuffaceous shale and sandstone, and thinning toward northeast. This formation unconformably overlies the Upper Permian Toyoma Formation. The Osawa Formation consists mainly of laminated shale with thin sandstone, and yields fauna of ammonoids, pelecypods, brachiopods, plants and reptiles. These ammonoids show the range from the Columbitan to Prohungaritan of SPATH (1930, 1934). In the western area, submarine slide deposits locally develop in the lower part of the formation. Such coarse elastics as conglomerate and sandstone with penecontemporaneous shale chips, are overlain by the slide deposits consist of rather fine material. Controversial intraformational conglomerate is, in my opinion, belonging to the lower part of the Osawa Formation, and is closely associated with the said submarine slide deposits. The Fukkoshi Formation consists of thickly bedded coarse-grained sandstone intercalated with thin shale and lenticular pebbly conglomerate. The Isatomae Formation consists of a thin alternation of shale and calcareous sandstone, sometimes intercalated with massively bedded shale and thick bedded sandstone. The shale in this formation is characterised by bioturbation. Paleocurrent data and lithologic facies change show that the deposition of Inai Group might have been initiated by sediment supply from the west into shallow marine environment. The basin became a little deeper during the deposition of the Osawa Formation. Coarse-grained sediments in the formation were supplied from the northwest and transported locally by the sediment-gravity flows. Submarine slide deposits are characterized by slump overfolds and dislocated blocks with welded contact to the adjacent rocks. Based on analyses of slump fold and welded contact submarine slide occurred on slopes inclined towards the southeast. These reconstructed paleoslopes are consistent with the paleocurrent data. The slide deposits were closely associated with sandstone and conglomerate directly underneath the deposits. The writer concludes that submarine slide was initiated by the mobilized coarse-grained sediments and fluidization of sand size sediments which are both underlying the slide mass and both locally transported from the source area during the deposition of lower to middle Osawa Formation.

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From a gravel quarry at the Otoebetsugawa Basin, near the southern margin of the Nopporo Hills, a horn of Bison and its cranial bone were discovered by workers there in 1972 (AKAMATSU et al., 1973). Since then, many fossil bones and teeth of mammals have been yielded from the same locality and have been collected by the workers. In 1980, the authors had opportunity to contact with them, and carried out geological survey to that gravel quarry and surrounding areas as well as identification for those fossil bones and teeth. The results of those studies are summarized as follows. 1. Amount of fossil bones and teeth attain more than 1400 specimens though fragmental. Up to now, the following specimens are identified: a fragmental pieces of elephant tusk and five molars of Mammuthus (assigned to M. sp. cf. paramammonteus and M. sp. cf. armeniacus); cranial (occipial) bone and horn of Bison sp.; two specimens of Artiodactyla extremities; two mandibula, many fragmental pieces of vertebrate and costae of Cetacea (Mystacoceti); a mandibula of Odobenus sp.; mandibula, humerus, costae and cranial bone of sea cow (Hydrodamalis sp.); fossil bones of other mammals. 2. As to the stratigraphic levels of those fossil bones and teeth, two horizons are discriminated; the lower is in the basal sand and gravel of the Shimonopporo Formation, while the upper is lain in the basal gravel of the overlying Otoebetsugawa Formation. The Kitahiroshima fauna of the former consists of Mammuthus sp. cf. paramammonteus, Hydrodamalis sp., Odobenus sp., Mystacoceti, Artiodactyla etc., and the Otoebetsugawa fauna of the latter comprises Mammuthus sp. cf. armeniacus and Bison sp.. 3. Although the Kitahiroshima fauna is representative of such mixed assemblage of marine and continental as Cetacea, Sirenia, Pinnipedia, Proboscedea and Artiodactyla, they are assumed to be autochthonous from the evidence of well preservation of fossils. Furthermore, it is probable that the sedimentary environment is estuary condition affected by cold current near the land. 4. From the stratigraphical, biostratigraphical (molluscan and pollen analysis) and magneto-stratigraphical studies, the Shimonopporo Formation ranges from the latest Early Pleistocene or the earliest Middle Pleistocene, and the Otoebetsugawa Formation belongs to the Middle Pleistocene. 5. Fossil elephant hitherto known in Hokkaido are Palaeoloxodon naumanni and Mammuthus primigenius, which characterize Middle to Late Pleistocene mammalian faunas. Therefore, it is significant that the presence of the Early to Middle Pleistocene mammals are confirmed in Hokkaido. The present findings may contribute in consideration of paleogeography of Hokkaido and migration route of continental fauna to the Japanese islands.

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