The Naganoken-seibu Earthquake of M6.8 occurred at 8 : 48a.m. on the 14th of September, 1984. It centered at about 35.5°N, 37.5°E. The hypocenters of the first and aftershocks were rather shallow, and were distributed within a small area on the southern slope of Mt. Ontake, a solitary volcano, 3063 m high, of Quaternary age. Large and small land slides triggered by the earthquake and associated mud flows devastated the villages and forests, and killed tens of men and women. Several members of the present authors were just surveying the geology of the area, and they, together with other members, made an urgen survey of the land slides and mud flows. The Quaternary strata of the southern slope of Mt. Ontake are classified as shown in the following table. [table] Among the four Quaternary formations the Tarusawa Formation, composed of thick series of lava flows, beds of tuff-breccias, volcanic mud-flows and beds of pyroclastic falls, is the main constituent of the present mass of Ontake Volcano, while the overlying Ohtaki Formation is composed of lava flows, beds of agglomerates, beds of tuff-breccias, beds of sand and gravel and aeolian volcanic ash beds. Significant is the remarkable unconformity between the two formations. In other wards, the rocks of the Tarusawa Formation had been eroded deeply, so that many deep and steep valleys and slopes were existent before the deposition of the Ohtaki Formation. Many of the land-slides occurred in the rock sequence of the Ohtaki Formation under the following conditions. 1) Many of the land slides (or collapses) occurred where thick beds of pumices and scoria of the Ohtaki Formation, overlain by inclined beds of lavas and tuff-breccias, accumulated in the valleys or on the slopes that had been eroded out of the Middle Pleistocene Tarusawa Formation. The Ohtaki Formation in and on the steeply inclined valleys and slopes were unstable from the beginning. 2) Where the basal surfaces of the Upper Pleistocene Ohtaki Formation made valley forms the groundwater gathered into the valley bottoms, and it expedited weathering and argillization of pumices and scoria. It also made easy to slide the overlying load. 3) The precipitation of the preceding five days had attained about 150 mm, which seeped into the rocks of the Upper Pleistocene Ohtaki Formation. It raised probably the groundwater table, and also increased pore-water pressure near the base of the deposits.

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In this paper we describe the fine structure of erupted pharyngeal teeth in Latimeria chalumnae. Pharyngeal teeth, situated on the medial side of the left first branchial arch, were obtained from Latimeria chalumnae (B. L. 175cm, B. W. 85kg, Female) and were used in this study. Cross stripes consisting of longitudinal and transverse grooves which penetrated into the surface layer were observed. Filmy structures were observed in the longitudinal grooves. It is thought that these filmy structures consist of organic matter, because these structures seemed to continue the dentin and disappeared after removal treatment for organic matter. A number of stripes almost parallel to the surface were observed in the section of the surface layer. These stripes were considered to be incremental lines. The stripes obliquely ended at the boundary between the surface layer and the dentin. Because the stripes nearer the surface ended closer to the basal portion and the stripes nearer the dentin ended closer to the apical portion, the pattern formed by these stripes resembles the incremental lines of mammalian enamel. Though the intervals between the stripes were 0.2-0.7μm, in this specimen the tendency was that form the intervals of the surface side to be narrower than those of the dentin side. The crystal-like granules of the surface layer were columnar or spindle shaped, 60-80 A in width and 600-800 A in length. Their width and length were relatively uniform. However, the arrangement of the crystal-like granules was irregular under high magnification. The outline of the crystal-like granules was never straight, but irregular. A number of fine electron-lucent spot-like, oval-like and line-like structures were seen in the crystal-like granules. It is considered that organic matter was present around the crystals of the surface layer, because fine networks which made us think of a negative view of the undemineralized section were seen after phosphotungstic acid (PTA) stain for undemineralized section on the grid. The boundary between the surface layer and the dentin was clear in observation with scanning and transmisson electron microscopes under low magnification. On the other hand, the boundary between the surface layer and the dentin became unclear in observation with a transmission electron microscope under high magnification and a mixed layer between the two, 0.3-1 μm in width, which was recognized from the density and arrangement of the crystal-like granules, was seen. Concerning the organic matrix of the dentin, the outermost layer of the dentin, 1-1.2 μm in thickness, which consists of electron-dense amorphous substances and loose collagen fibers, was recognized in the specimen after chromium sulfate demineralization. From the results described above, it is considered that the surface layer of the pharyngeal teeth in Latimeria chalumnae corresponds to true enamel because of its optical property, resolvability to acid, mineralization, fine structure and feature of organic matrix. In particular, the feature of the surface layer resembled the thin aprismatic enamel in amphibia.

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The Pliocene molluscan fauna of the Annogawa Formation in the Sasagami hills, Niigata Prefecture, is described and analysed. 1. The Annogawa formation is mainly composed of massive sandy siltstone. At locality 1 this formation includes some conglomerate lenses in the middle horizon and molluscan fossils occur densly in them with some other invertebrate remains. It is assumed that all of them are allochthonous in occurrence, because shells are fragmental and most of bivalves are disarticulated. They can be divided into four types of assemblages based on the bathymetrical range, the bottom character and^the life form of living equivalent species as follows. Type i: Dwellers of gravelly or sandy bottom from the intertidal to the upper sublittoral zones. Type ii: Infaunal dwellers of muddy bottom from the intertidal to the lower sublittoral zones. Type iii: Infaunal dwellers of muddy bottom in the lower sublittoral zone. Type iv: Epifaunal dwellers of gravelly bottom from the intertidal to the lower sublittoral zones. They are sessile or adhering. One attempt was made whether the bottom character of each type was correspond to the sedimentary facies of the Dainichi Formation or not. This analysis leads to the following-conclusion : the assemblage is composed of a part of the "biocoenosis" of muddy bottom in the lower sublittoral zone (Types ii and iii) and transported elements from various biotopes in the intertidal and the upper sublittoral zones (Type i and a part of Type iv). 2. From the result of the analyses of the molluscan fauna, it is assumed that the Annogawa Formation was deposited in the lower sublittoral zone and that an intertidal zone near by shore was developed not so far from there in the same age. 3. This fauna characterized by the elements of open-sea muddy bottom (Nuculacea, Pandorella and so on) is older than the Plio-Pleistocene Haizume fauna (KOBAYASHI, 1983) which includes many endemic species of the Omma-Manganji fauna. 4. Occurrence and characteristic form of cylindrical trace fossils created by Pholadidae pelecypods are described in outline.

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The Ryoke Belt in the central part of the Awaji Island is composed mostly of granitic rocks with minor amounts of metabasites and metasediments. The Sennan Group is found at the southern border of the Ryoke Belt, and the granitic rocks and the Sennan Group are intruded by many dykes of two stages, the older and the younger. The granitic rocks can be divided into six rock-masses which are grouped as follows, based on their stages of intrusion; 1 st stage Shioo and Tsushigawa granites 2 nd stage Shizuki, Sumoto and Ei granodiorites 3 rd stage Senzan granite The first stage granites are intruded by dykes of the older stage and granitic rocks of the second to third stages. The second stage granodiorites intrude also into the older stage dykes and the Sennan Group which consists of acid pyroclastics. The Senzan granite of the third stage is massive and intrudes discordantly into the Sumoto granodiorite of the second stage as well as the Tsushigawa granite of the first stage. The first stage granites, the dyke rocks of the older stage and the Shizuki granodiorite of the second stage are more or less mylonitized and schistose. It is considered that the main mylonitization in the area took place under a condition of relatively low temperature before the intrusion of the Ei granodiorite.

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Fission-track dating was carried out on six volcanic materials (one tuff layer, two rhyolitic lavas and three pyroclastic flow deposits) in Southern Kyushu by GBGRE method (YOKOYAMA, 1983). They are as follows; [table] These radiometric ages do not contradict the stratigraphical evidence shown in Fig. 3 and 13.

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It is still in argument, whether the plates existed and their movement controlled the tectonics of earth crust during Proterozoic time. In this paper the authors present an example of the middle-late Proterozoic plate movement and the result thereof discolsed in Southeast China. The Jiangnan Proterozoic mobile belt is located in the vast areas from the Kuaiji Mountains and the Longmen Mountains in east Zhejiang Province, through the border mountains of Zhejian, Anhui and Jiangxi Provinces, the Poyang Lake in north Jiangxi Province and the Dongting Lake regions in north Hunan Province, and the Xuefeng Mountains in west Hunan Province, to the Jiuwandashan Mountains in north Guangxi Zhuang Autonomous Region, roughly corresponding to the Chiangnania of Huan (1945), structurally in the conjunction between the Yangzi platform and Southeast China, where the Caledonian foldbelt forms a striking arcuate tectonic zone. Since the 1970s the present authors have devoted themselves to making a research on rock types, sedimentary formations, and tectonic evolution of the Jiangnan Proterozoic region in terms of the plate tectonic concept, and they suggest that the Southeast China oceanic plate subducted toward the Yangzi continental plate during Proterozoic time, and the Jiangnan Proterozoic trench-arc-back arc basin system was originated. This tectonic system experienced the Dong'anian, the Laokedongian, and the Xuefengian orogenies. In the light of analysis of the sedimentation and tectonic setting of the Sibao Group, the oldest exposed strata in the study area, it is revealed that the border region between the Yangzi continental crust and the Southeast China ancient oceanic crust was a passive continental margin during the early stages of the Dong'anian tectonic cycle. In the course of the Dong'anian cycle, the subduction of the Southeast China oceanic plate against the Yangzi continental plate took place, and consequently an embryo of the Jiangnan Proterozoic trench-arc-back arc basin system appeared. In the Xuefengian cycle, the Southeast China oceanic plate subducted toward the Yangzi continental plate inherently or newly in different parts of the island arc. The Xuefengian orogeny swept across all strata of trench-arc-back arc basin system of the Dong'anian and the Xuefengian cycles, producing a huge anticlinorium belt and giving rise to a regional metamorphism of the greenschist facies. Finally, huge granitic batholiths were emplaced, and a granitic and gneissic layer representing a continental crust of the Jiangnan Proterozoic mobile belt was formed.

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