小笠原諸島(父島・母島)の土壌中の動物珪酸体"Opal Sponge Spicules"について

概要

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The classification, morphologies and mode of occurrence of opal sponge spicules, in the soils, distributed in the Bonin (Ogasawara) islands were investigated. The results obtained were summarized as fellows: 1) The Bonin (Ogasawara) Islands comprise the southernmost teritory of Japan ; they are located in the Pacific Ocean 1,000km south of Tokyo. The Bonin Islands are oceanic islands which have been connectied with the main land since their emergence by the volcanic actibity in the Tertiary (pillow lava of Boninite, breccia, andesite, tuff breccia and Limestone). Each islet of the Ogasawara are small and consist of large bluffs and mountains have few coastal plain. 2) The contents of animal opals were rich in marine deposits of Tertiary and mixed layer from foreign opal sponge spicules. 3) The animal opal in soils were morphologically divided into seven types. They are monaxon type, diaxon type, tryaxon type, tetraxon type, polyaxon type, desma type and sterrasters type in table. 2. 4) Optical character of animal opals were distinguishable under microscope, colorless or pale pink color, dark in cross nicols.
1992-12-31