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The pronounced correlation between mineral composition and grain-size in sedimentary deposits is attributed to hydraulic sorting during transportation. The hydraulic equivalence is realized in the for...m that the mineral composition of grains ill a fixed settling velocity interval is maintained constant during the transportation by suspension. One of the Quaternary pyroclastic fall deposits in Hokkaido, Spfa-1 is wide-spread and shows a remarked lateral textural variation. The settling velocity of constituent grains such as pumice, lithic and free crystals were measured in relation to grain size. And the mineral composition in a fixed velocity interval was proved to be almost constant at every points along the disposal line. This result was applied to two different Cretaceous sandstone formations in Hokkaido. The modal and textural analyses showed that the turbidite sandstones from the Kanayama area have had a distinct grain-size-controlled variation, while those of the other shallow-marine sandstones from the Furano area was variable and less size-controlled. The former variation pattern can be interpreted to have been resulted from hydraulic sorting on primarily well-mixed, homogenized source. These modal variation patterns give useful information on the mode of transportation and on the homogeneity of the source material.続きを見る
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Mendeley出力
26_03_p243