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[HGM14-P07] Fluvial breaking and abrasion mechanisms acting upon gravel–sand grains utilizing the difference of grain lithology
Keywords:gravel–sand, breaking and abrasion mechanisms, lithological composition, roundness, Ashio Mountains
The downstream increase in chert/shale ratio of cobble–pebble and downstream rounding of shale pebble–sand grains occurred, in spite of a low chert detrital supply. The results suggested that pristine sand grains were produced from gravels and sands by breaking mechanism, which leads to grain size reduction and higher angularity, and by abrasion mechanism, which gives rise to grain rounding while keeping nearly unchanged size and produces angular pristine produced finer particles, during transport, considering with the existence of changes in chert grains roundness. Additionally, the contrasting trend of downstream roundness changes between the two rivers is recognized, which might have been caused by the different gradients among the researched section of the rivers. Therefore, it is possible to reveal the relationship between the river gradient and breaking and abrasion mechanisms in this study.
This study was supported by the Sasakawa Scientific Research Grant from The Japan Science Society.
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