The herringborn shaped magnetite is disseminated in the groundmass of Takayama picritic sheet. This peculiar shaped magnetite is considered to be a product of the dendritic growth. Three dimensional morphology of such magnetite through reflecting and electron microscopic studies was made clear, which indicates that a normal section to a crystal axis of herringborn magnetite represents cruciform magnetite appearing universally in the groundmass. Compared with the cooling rate of picrite from the Mineoka Belt, the formation of herringborn magnetite in Takayama picrite depends not only on the rapid cooling process but also on the more magnetite concentration in the Takayama original magma.

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In the former report (TAMBA BELT RESEARCH GROUP, 1979), the lithofacies and geologic structure of the Paleozoic and Mesozoic formations (Tamba Group) of the Northwestern hills of Kyoto City had been described. In this report, occurrences of conodont fossils of Permian and Triassic age in this region are treated. Middle to Upper Triassic conodont fossils are found abundantly, namely, Gladigondolella tethydis, Paragondolella polygnathiformis, Metapolygnathus abneptis, M. bidentatus etc.. In some region, these Triassic conodont fossils occurred in succession with stratigraphic order, and repeatedly by faults. Permian conodont fossils are found near the occurrence of fusuline fossils, namely, Sweetognathus whitei, Neogondolella spp., Neostreptognathodus sp. indet., etc.. The Permian and Triassic formations are noticed in conformable relation. Correlation between the formations of the Maizuru and Tamba Belts is discussed. The Triassic formations of the Maizuru Belt are represented by neritic shelf facies. On the contraly, the Triassic formations of the Tamba Belt are eugeosynclinal facies, and show continuation of the Honshu geosyncline to the late Triassic Period. Lithofacies of the Upper Triassic formation shows remarkable contrast between areas in this region. Slate-shale and chert facies and coarser clastic facies are separated by Schalstein occurrece, and this relation may be suggests some topographic nature in the sedimantary basin.

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[in Japanese]

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The seventh excavation of Lake Nojiri(Nojiri-ko), which was carried out from March 25th to April 1st of 1978, made a success of digging out numerous fossils and artifacts from the Latest Pleistocene Nojiri-ko Formation, distributed in the bottom of the lake. In the course of the cleaning of these fossils, several teeth of rodents were found by sieving the fine sands which were adhered to a bone fragment of fossil elephant. Since the occurrence of the Pleistocene micro-mammalian remains in Japan have been known exclusively from cave and fissure filling sediments, it can be said that these are the first rodent fossils discovered from the Pleistocene sediments outside of caves and fissures. They are described as follows: Order Rodentia Suborder Myomorpha BRANDT, 1855 Family Cricetidae ROCHEBRUNE, 1883 Subfamily Microtinae MILLER, 1896 Genus Microtus SCHRANK, 1798 Microtus sp.(Figs. 4-5; P1. 1, Figs. 1a-1d) Material: Two specimens of right M₂ (specimen numbers: 7NIIIS18-34, 7NIIIS18-35). Locality: Bottom of Lake Nojiri, Tategahana, Shi nano-machi, Kamiminochi-gun, Nagano Prefec ture (long. 138°13′E, 1at. 36°50′N) Horizon: Upper Nojiri-ko Formation I (Latest Pleis tocene, 16150±550 yr. B.P., Gak-267 in ¹⁴C age). Description: The material are represented by only two fragmental right M₂. It is assumed that they originally have two lingual and two buccal triangles, and one posterior loop. The most part of the posterior loop is damaged in 7NIIIS18-34. The posterior loop, and the most part of second and fourth triangles counting from the posterior part, are lost, in 7NIIIS1835. Both specimens are grayish to dark brown in color, and rootless. The crown with prismatic shape is strongly curved buccally. Each salient angle is pointed. The lingual triangles are larger than the buccal ones. Each triangle is independent, not confluent with each other. Cementum is observed in each reentrant fold. Demensions and method of measurement are given in Table 1 and Fig. 2 respectively. Comparison and remarks: The materials are easily distinguished by their enamel pattern from Clethrionomys, Eothenomys, Aschizomys and Myopus, which are representative genera of subfamily Microtinae known from the Pleistocene and Recent of the Japanese Islands and their adjacent areas. The present materials are characterized by their rootlessness, pointed salient angles, closed triangles and cementum in reentrant folds. These characters are well coincident with those of the genus Microtus. The specific characters of the genus are present in the enamel pattern of M₁ and M³ of the most species. As our materials are only two isolated M_2, further discussions are impossible. Myomorpha, gen. et sp. indet.(Figs. 6-7 ; P1. 1, Figs. 2a-2c) Material: One specimen of right lower incisor(7NIIIS18-33). Locality and horizon: Same as above mentioned molars of Microtus sp. Description: The material is only one fragmental lower incisor with somewhat damaged occlusal surface. Dentine of lingual side is fairly lost and dark brown to black in color. Enamel is almost preserved and yellowish gray in color, which forms a thin cover of labial side as in usual rodent incisors. In cross section, the enamel is U-shaped, which thickens in the central portion and gradually thinned towards the both ends(Fig. 7). The surface of the enamel is smooth trom front to rear. Demensions and method of measurement are shown in Table 2 and Fig. 3 respectively. Comparison and remarks: The material has shape and size quite similar to the incisor of myomorph rodents of the living and Quaternary forms of Japan. As the rodent incisor is less characteristic from taxonomic viewpoint, the present material is insufficient for more precise determination.

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The surveyed region is one of the Southern Igneous Activity Regions (NAKAYAMA, 1962) in the Sambagawa metamorphic belt. In the western area of the region, the Chichibu Palaeozoic formation consisting of sandstone, shale and chert is distributed, but in the central and eastern area, submarine basic effusive rocks (pillow lava, pillow breccia, hyalloclastite) are in company with tholeiitic gabbro (NAKAYAMA et al., 1973), ultramafic rocks and sheet complex consisting of small gabbroic bodies. The area occupied by submarine basic effusive rocks is a depressed area in the HONSHU Eugeosyncline. The phenocrysts of basic volcanic rocks are olivine, clinopyroxene and plagioclase, and groundmass of these rocks consist of clinopyroxene and plagioclase. But these minerals are altered except for the phenocrysts of clinopyroxene by the Sambagawa regional metamorphism. These basic volcanic rocks are overlaid by acidic tuff, which originates in the acidic volcanism of the Chichibu terrain. In this region hypabyssal intrusion which took place during the movement, is associated with the upheaval of the depression area. The largest gabbroic rock in the region, which is named Kamiyama gabbro in this paper, is a tholeiitic differentiated rock based on a crystallization trend of the clinopyroxene. The differentiation of the tholeiitic magma took place in situ. The petrographic characters of gabbros which intruded as sheet into the basic effusive rocks, correspond to these of the differentiated rocks of the Kamiyama gabbro. "Peridotites" composed of olivine, Ti-augite, Ti-pargasite and Ti-biotite and gabbros have a close relationship in chemical composition of pyroxene and amphiboles. In the amphiboles of the cumulate and gabbros, (Al^<VI>+Ti) content, especially Ti content vary successively. Kamiyama gabbro and gabbros of sheet complex are crystallization products of the magma, which is the greater part of the original magma, and the cumulates were early crystallized from a very small part of the original magma in the magma chamber. The greater part of the cumulates intruded as solid intrusion along fault. Opaque minerals in the sheet rocks and Kamiyama gabbro are altered and the chemical composition of parts of one crystal is variable. Therefore, the chemical composition of the mineral can not be determined, but rarely original minerals are present as relict in some rocks. The relict minerals are ilmenite. Cr-rich clinopyroxenes are situated in the range from 0.80 to 0.90 in MgO/MgO+FeO ratio, but the clinopyroxenes of the range do not always have high Cr content.

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