The influence of aeolian dust in non-allophanic Andosols on Yakushima Island(Soil genesis, classification and survey)

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The oxygen isotope (δ^<18>O) composition of quartz and the d_<(060)> values of clay minerals were determined from four pedons of non-allophanic Andosols derived mainly from the Holocene volcanic ash on Yakushima Island. These soils contained considerable amounts of aerosol-sized (1-10μm) and coarse (>53μm) quartz. The δ^<18>O values for the aerosol-sized quartz ranged from 14.7‰ to 17.4‰, which was comparable to or slightly lower than known values for loess-derived Red and Yellow soils on Tanegashima Island located approximately 20km east of Yakushima Island. The abundance and δ^<18>O values of the aerosol-sized quartz indicated that non-allophanic Andosols on Yakushima Island were strongly influenced by aeolian dust. However, the presence of coarse quartz implied that granite-derived materials were also incorporated into non-allophanic Andosols. X-ray diffraction patterns for most clay minerals showed two broad peaks around 0.154 and 0.150nm, respectively. The d_<(060)> values confirmed that 2:1-2:1:1 clay minerals consisted of dioctahedral and trioctahedral clay minerals. Since aeolian dust contains little or no coarse quartz and trioctahedral clay minerals, the abundance of coarse quartz and trioctahedral minerals confirmed that the occurrence of non-allophanic Andosols on Yakushima was influenced by biotite-granite, in addition to aeolian dust.
一般社団法人日本土壌肥料学会の論文
2012-04-00