Earth Surface Movement Inferred from Grain-size Variation in Pond Sediments

通过对六廓山池塘沉积物的粒度分析，发现在过去50年的粒度序列中，存在着重砂年份。这些年份在粒度分布上表现为显著的粗化。在山区强降雨区，利用该粗层进行了年代际沉积物与年代际沉积物的交叉。通过使用^ Cs数据的峰值，将距离该地区稍远的池塘沉积物与山区池塘的沉积物交叉定年<137>。粒度分布的变化表明，山区和山区西侧的池塘侵蚀和沉积环境不同，强降水区粗化明显，弱降水区粗化不明显，这与暴雨时的降水分布有关。这些结果表明，粒度分析可以为重建近10^1-10^2年的侵蚀环境提供一个非常有用的工具。

Grain-size analysis of pond sediments in the Rokko Mountains shows that years of heavy rainfalls can traced in the grain-size sequences for the past 50 years. These years show up as prominent coarsenings in the grain-size distribution. This coarse layer was used to cross date undated sediment to dated sediment in the heavy rainfall area in the mountains. Sediment from a pond somewhat distant from the area was cross-dated to sediment in the mountain pond by the use of peak values of ^<137>Cs data. Changes in grain-size distribution show differences in the erosional and sedimentary environments of the ponds in the mountain area and in the area just to the west of the mountains ; prominent coarsening severe heavy rainfall area and non prominent coarsening in less heavy rainfall areas that are correlated with rainfall distribution in times of heavy rain. These results show that grain-size analysis can provide a very useful tool for reconstructing the erosional environments during the past 10^1-10^2 years.