著者

宇津川 徹 細野 衛 杉原 重夫

出版者

日本ペドロジー学会

雑誌

ペドロジスト (ISSN:00314064)

巻号頁・発行日

vol.23, no.2, pp.p134-144,図4p, 1979-12

被引用文献数

1

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The morphologies of animal opal, "Opal Sponge Spicules" in the tephras, distributed in Ichihara districts in Chiba prefecture were investigated. The results obtained were summarized as follows ; 1) The tephra deposits at the localities of Figure 1. in Ichihara terrace land were Anegasaki Formation (mainly AW type tephra) (AF), Shimosueyoshi Loam (SL), Musashino Loam (ML) and Tachikawa Loam (TcL). 2) The contents of animal opal were rich in Anegasaki Formation and Shimosueyoshi Loam, as shown in Figure 2. 3) The animal opals found in tephras were morphologically divided into eight types. They are diaxon type, tryaxon type, tetraxon type, polyaxon type, sterrasters type, desma type, lattice type and anthasters type in table 1. 4) The size of diaxon type animal opal was 100-1100 μ in length, 20-100 μ in width, tryaxon type animal opal was 100-400 μ. in length, 30-80 in width, tetraxon type animal opal was 500-800 μ in length, 70-120 μ in width, polyaxon type animal opal was 150-750 μ in length, 40-70 μ in width, sterrasters type animal opal was 100-200 μ in length, 100-220 μ in width, desma type animal opal was 400-800 μ in length, 30-100 μ in width, lattice type animal opal was 400-900 μ in length, 30-100 μ in width, anthasters type animal opal was 100-500 μ in length, 10-30 μ in width. 5) Except for sterrasters type, there were wide and narrow openings in tubes, some were stuffed with foreign materials. Fragments of spicule type had tubular form the diameter of which was 2-30μ. 6) Optical character of animal opal was distinguishable under microscope, colorless or pale pink color, dark in cross nicols (indirect procedures). The refractive indices of diaxon type animal opal was ; n=1.452-1.453, the refractive indices of sterrasters type animal opal was ; n = 1.440-1.446. Spicules of Recent opal sponge (Sponge spicules of a opal sponge of Sagami Bay) was colorless and transparent. The refractive indices of diaxon type spicules of Recent opal sponge was ; n = 1.441±, the refractive indices of sterrasters type of Recent opal sponge was ; n = 1.440±. From these facts the animal opals were non-crystalline (amorphous).