Earth Science (Chikyu Kagaku)
Online ISSN : 2189-7212
Print ISSN : 0366-6611
Volume 53, Issue 1
Displaying 1-9 of 9 articles from this issue
  • Toshio Kusunoki, Makoto Musashino
    Article type: Article
    1999 Volume 53 Issue 1 Pages 1-2
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
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  • Shogo Konishi, Keiichi Takahashi
    Article type: Article
    1999 Volume 53 Issue 1 Pages 3-18
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
    The authors examined the mandibular features of stegodons, Stegodon aurorae and Stegodon shinshuensis through the investigation of mandibles from the Kobiwako group of Taga Town, Shiga Prefecture, central Japan. For this examination, mandibles of six species of Stegodon and those of five species of Elephantinae were used. We observed especially the median section of mandibular symphyses and a cross-section of the mandibular bodies of these specimens. Differences in characters between stegodons and Elephantinae are: 1) the cross-sections of the bodies of Stegodon are more slender and the lateral surfaces of the bodies are flatter than those of Elephantinae; 2) a groove in the medioventral side of the body is observed in some species of Stegodon, while it is not observed in Elephantinae; 3) most of the symphyseal sections of Stegodon are more elongated antero-posteriorly than those of Elephantinae and the Stegodon's intraspecific variation in shape is higher than that of Elephantinae; 4) the posterior ends of the mandibular angles of Stegodon are flatter medio-laterally, but those of Elephantinae are round, and the mandibular angles of the Stegodon are not so expanded as those of the Elephantinae. 5) regarding the arrangement of molars in the specimens prior to M2 stages, the successor and predecessor of almost all stegodons are placed on the same plane, however, in Elephantinae, the successor is slightly inclined forward at the mesial. These characters are considered to be related to the relatively long mandibles of the Stegodon. Moreover, the authors were able to determine the specific characters of S. aurorae in the Stegodon: 1) the anterior end of the body is steeply inclined in S. aurorae; 2) the median section of the symphysis is shorter antero-posteriorly than in other Stegodon; 3) in the M1 stage specimen, the successor is arranged in the posteroventral side of the predecessor, and in the M3 stage specimen, the bending convex to lingual of the third molars is strong. These findings suggest that the mandible of the S. aurorae is closely connected to the antero-posterior shortening of the mandible as observed in the Elephantinae. The authors confirm the evolutionary trend of the mandible among the considered mandibular features of S. aurorae. It is suggested that S. aurorae has the same trend as that observed in the Elephantinae. We also believe that Stegodon zdanskyi is a separate species because of the more advanced shortening of S. shinshuensis.
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  • Yoshifumi Kishigami, Kazumi Sakurayama, Kazue Tazaki, Masato Ueshima, ...
    Article type: Article
    1999 Volume 53 Issue 1 Pages 19-28
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
    Ogoya Mine in Ishikawa Prefecture, Japan, is one of the fissure-filling vein type copper deposits in the Green Tuff region. The mine contains pyrite, chalcopyrite, galena and sphalerite. Heavy metal ions dissolveed from abandoned metal-mine are common in waste water pool and stream. In the metal mining area, Fe, Cu, Zn and Cd are releasing from dumping area to the Kakehashi River. The drainage water contains Fe (26.85mg/l), Cu (3.97mg/l), Zn (23.94mg/l) and Cd (0.09mg/l). In this mine, various colored microbial mats (biomats) are grown around the No.6 pit drainage system. Abundant brown biomats covered with green biomats have fixed heavy metals on the drainage channel down the pithead. These biomats are observed by both optical and scanning electron microscopes (SEM). Minerals in the biomat and their chemical compositions were analyzed by X-ray diffraction (XRD), X-ray fluorescence (XRF) and energy dispersive X-ray analyzer (EDX). The reddish biomats fix Cu selectively from drainage water, whereas the dark green biomats fix Fe. Microorganisms, such as bacteria and algae, capture most of heavy metals as Fe- and Cu-minerals in/on the cell. It is clarified that copper and cuprite are formed in reddish biomats, and that goethite and maghemite are formed in the brown biomats.
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  • Yoko Tashiro, Kazue Tazaki
    Article type: Article
    1999 Volume 53 Issue 1 Pages 29-37
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
    Brownish yellow microbial mats growing along the Kakuma River and at the controlling pond in the Kakuma Campus of Kanazawa University are of predominantly iron oxidizing bacteria, such as Leptothrix sp., Gallionella sp. and Toxothrix sp. Those microbial mats use ferrous ions as their energy source through the oxidation into ferric ions. Transmission electron microscopy of the primitive microbial mat, have revealed mucoid substances of Toxothrix sp. like polysaccharides are effective for adhesion of iron hydroxides produced through biomineralization of Toxothrix sp. Iron hydroxides coated with mucoid substances are coagulated into colloidal particles 200nm in size. Such condensed colloidal iron hydroxides grow into the aggregates and subsequently may be expelled outward from the thin membrane of polysaccharides. It is suggested that polysaccharides of Toxothrix sp. prevent dispersion of iron hydroxides and promote coagulation of iron materials. Such a condensation process of iron hydroxides is considered to be a factor for increasing the thickness of microbial mats.
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  • Masakazu Hayashi
    Article type: Article
    1999 Volume 53 Issue 1 Pages 38-52
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
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    In the Upper Pliocene to Lower Pleistocene Kazusa Group of the western hills of Kanto Plain, fossil donaciine beetles occur in relative abundance. Six species from this group in Saitama Prefecture are described, and the species composition is compared with those from the adjacent Pleistocene deposits. The phylogeny and the geographic history of Plateumaris dorsata Hayashi, 1997, described from this group, is discussed on the basis of the morphology, geographic distribution and fossil records of the related extant species.
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  • Numazawa Collaborative Research Group
    Article type: Article
    1999 Volume 53 Issue 1 Pages 53-70
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
    Numazawa volcano located in the western part of Aizu, Fukushima Prefecture, is a small volcano having a single caldera lake, which has been erupted since the Late Middle Pleistocene (about O.13Ma). The long axis of the caldera lake formed in the last stage of volcanic eruption is similar to that of the old caldera formed during the Pliocene Period. Volcanic successions are divided into the seven units as follows: Sohyama lavas, Mizunuma pyroclastic formation, Mizunuma formation, Ohkuriyama lavas, Hayato pyroclastic formation (51ka), Numazawa pyroclastic formation (before 5000years), and Numazawa formation, in ascending order. Sohyama lavas consist of augite-hypersthene dacite (SiO_2 63-68%). Mizunuma pyroclastic formation consists of pyroclastic flow deposits of biotite rhyolite (SiO_2 75%). Ohkuriyama lavas consist of biotite-hornblende dacite (SiO_2 65%). whereas Hayato pyroclastic formation is composed of lava, welded tuff and pyroclastic flow deposits. They are dacitic (SiO_2 68-70%) in composition containing biotite, hornblende and cummingtonite. Numazawa pyroclastic formation is also dacitic (SiO_2 65%), but it contains hypersthene and hornblende. It is composed of pyroclastic flow deposits with banded pumices formed by mixing of andesite and dacite magmas. Mizunuma formation and Numazawa formation are consisted of fluvial gravel beds. Chemistry of the volcanic rocks from Numazawa volcano is similar to that of the Moriyoshi volcanic chain of the Quaternary volcanoes of the NE Japan.
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  • Kikuji Matsuoka
    Article type: Article
    1999 Volume 53 Issue 1 Pages 71-74
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
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  • Tatuo Inoue, Keisuke Nagao, Kazue Tazaki, Yoshihiro Kawatani
    Article type: Article
    1999 Volume 53 Issue 1 Pages 75-80
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
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  • Mutsumi Nakai
    Article type: Article
    1999 Volume 53 Issue 1 Pages 81-82
    Published: January 25, 1999
    Released on J-STAGE: July 14, 2017
    JOURNAL OPEN ACCESS
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