現地調査と室内実験によるビーチロック形成メカニズムの検討

山木 克則; 茅根 創; 大葉 英雄; 洪 永勲; 山本 将史; 田中 昌宏; 林 文慶; 上野 嘉之

doi:10.2208/jscejoe.72.I_916

Annual Journal of Civil Engineering in the Ocean Vol.32

STUDIES ON THE BEACH ROCK FORMATION MECHANISM BY FIELD SURVEYS AND LABORATORY EXPERIMENT

Katsunori YAMAKI, Hajime KAYANNE, Hideo OHBA, Nobuhiro KO, Shoji YAMAMOTO, Masahiro TANAKA, Boon Keng LIM, Yoshiyuki UENO

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Keywords: beach rock, coral reef, foraminifera, algae, cyanobacteria, fine particle, Ishigaki Island, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX)

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2016 Volume 72 Issue 2 Pages I_916-I_921

DOI https://doi.org/10.2208/jscejoe.72.I_916

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Abstract

To clarify formation mechanism of the beach rock, a recently forming beach rock was observed by viewpoints of ecology and civil engineering in the field, and solidification test of the coral grit was conducted in the laboratory. At the field survey of Yoshiwara shore in Ishigaki Island, a modern artifact in the beach rock was observed. This phenomenon was considered that this beach rock is relatively new formation and it continued in the formation process. Adhesion of green algae and cyanobacterium was observed on the beach rock surface. Cement materials including Ca, Mg and Si were detected by SEM-EDX observation.
In the indoor experiment, periodic change of the organic matter acidization and alkalinization which linked ebb and flow was determined. As a new finding, eluviation and crystallization of Ca were deeply related to the beach rock formation.

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