The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 121 , Issue 6
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  • Takaharu Sato, Keiko Suzuki-Kamata, Yutaka Wada, Takeshi Nakajo
    2015 Volume 121 Issue 6 Pages 173-178
    Published: June 10, 2015
    Released: July 30, 2015
    JOURNALS FREE ACCESS
    The Miocene Sekibutsu Tuff Member at Nara, central Honshu, Japan, consists mainly of pyroclastic flow deposits and reworked volcaniclastic deposits. The pyroclastic flow deposits, which could have been deposited at some distance from the source calderas, occur in the lower part of the member and are subdivided into three units based on pumice content and size (in ascending order: units L1, L2, and L3). Unit L1 consists of several layers of lapilli tuff and tuff breccia interbedded with thin layers of sandstone and mudstone. The matrix of the tuff breccia includes sand-sized mudstone clasts, and the breccia contains an irregularly lens-shaped pumice-rich zone that is several meters wide. Unit L2 consists of massive tuff with a small amount of lapilli-sized pumice. Unit L3 comprises lapilli tuff and lithofacies similar to those of unit L1. Reworked volcaniclastic deposits constitute the upper part of the member. The deposits are unconformably overlain by pyroclastic flow deposits.
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  • Kazuhiro Suzuki, Koichi Mimura, Shinji Inagaki, Makoto Takeuchi
    2015 Volume 121 Issue 6 Pages 179-183
    Published: June 10, 2015
    Released: July 30, 2015
    JOURNALS FREE ACCESS
    Three pieces of coniform conodonts were discovered in the Aso limestone body in Fuketsu Cave, Chichibu Belt, Mie Prefecture. Although the genera and species of the discovered conodonts have not been identified, they have features similar to those of Late Triassic conodonts (e.g., Zieglericonus rhaeticus Kozur and Mock). Our discovery of conodonts and further studies of the limestone may yield important information on the geological history and conditions of formation of the Aso limestone body.
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  • Takehisa Tsubamoto
    2015 Volume 121 Issue 6 Pages 185-189
    Published: June 10, 2015
    Released: July 30, 2015
    JOURNALS FREE ACCESS
    Two rare anomalous dental morphologies were observed in living Japanese raccoon dogs (Nyctereutes procyonoides viverrinus). One specimen exhibits an extra third root on P3, and the other exhibits a mesiodistally shortened, buccally swelled, and occlusally triangular P4. Analogous morphologies also occur in two Eocene mammalian species, Brachyhyops viensis and Brachyhyops trofimovi (Artiodactyla; Entelodontidae). Brachyhyops viensis has a third root on P3, and B. trofimovi has a mesiodistally shortened, buccally swelled, and occlusally triangular p4. These morphologies of the Eocene species have been considered as diagnostic at the species level. However, the presence of analogous dental morphologies in the anomalous teeth of the raccoon dog imply a possibility that a part of the species diagnoses of B. viensis and B. trofimovi may be not diagnostic characters but anomalous morphologies.
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