Earth Science (Chikyu Kagaku)
Online ISSN : 2189-7212
Print ISSN : 0366-6611
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Research Article
  • Obstacle scour marks containing trace fossils from the Miocene Morozaki Group in the Chita Peninsula, Aichi Prefecture, central Japan
    Koichi FUTAMURA, Masatoshi YAMAOKA
    Article type: Research Article
    2024 Volume 78 Issue 1 Pages 1-14
    Published: January 23, 2024
    Released on J-STAGE: March 30, 2024
    DOIhttps://doi.org/10.15080/agcjchikyukagaku.78.1_1
    JOURNAL FREE ACCESS
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    The horseshoe furrows and ridge structures were observed around the mound that contained the trace fossil (burrow) from the Toyohama Formation of the Miocene Morozaki Group in the Chita Peninsula, Aichi Prefecture, Japan. The morphological characteristics of these structures were examined and determined as obstacle scours. However, no rigid bodies, such as gravel or shell or obstacles from the bottom surface were observed on the mound that contained the burrow. It might be highly probable that the halo core of the burrow which was hardened by the mucus of the trace-former, or the trace-former itself or both, played the role of an obstacle in this structure.

    In the upper deep-sea zone, benthic animals formed burrows and colonies on the seafloor surface, where the bottom sediment consisted of silt. The obstacle scours were formed by horseshoe vortexes around the obstacles due to turbidity currents, which contained medium-grained sand flowing onto the seafloor surface from S15˚W direction.

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Short Report
  • “Gishiki Onsen”, the mysterious hot spring ruins that existed at the southwest foot of Bandai Volcano
    Shigeki CHIBA
    Article type: Short Report
    2024 Volume 78 Issue 1 Pages 15-20
    Published: January 23, 2024
    Released on J-STAGE: March 30, 2024
    DOIhttps://doi.org/10.15080/agcjchikyukagaku.78.1_15
    JOURNAL FREE ACCESS
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    On April 12, 1987, the author found traces of a hot spring, during the geological survey at the southwestern foot of Bandai volcano. I searched old documents regarding this hot spring but there was no record, and it was “the mysterious hot spring” for a long time. On November 2011, I found and purchased an old sightseeing guide paper “View of Bandaisan Shrine and Enichiji Temple” at an antiquarian bookstore. The guidebook was published in 1906, and most of the content was an explanation of Enichiji Temple, but Mt. Bandai was included in the picture. On the part of Mt. Bandai in the picture, there was a illustration of the wooden house and the word “Gishiki Onsen”. With this discovery, there is a high possibility that the mysterious hot spring is “Gishiki Onsen”.

    On May 4, 2021, I conducted a field survey again and recorded the current state of the hot spring site. The hot spring site was located at 140°02′36″E, 37°35′55″N. And the size of the site was approximately elliptical with a width of about 16 m x 14 m.

    Looking at old topographic maps, at the location of “Gishiki Onsen” there is a symbol for mineral springs in 1926 but not in 1933. Therefore, it is understood that “Gishiki Onsen” existed at least from 1906 to 1926, from the changes of old pictures and topographical maps.

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