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

对六高山湖泊沉积物粒度序列的分析表明，近50年来，湖泊沉积物的粒度序列可追溯暴雨年份。这些年在粒度分布上表现为明显的粗化。利用这一粗层进行了山区强降雨区无定年泥沙与定年泥沙的对比。利用^<137>Cs的峰值数据，将离该地区较远的一个池塘的沉积物与山区池塘的沉积物进行了交叉测年。粒度分布的变化表明，山区和山西侧水塘的侵蚀和沉积环境存在差异；强暴雨区显著粗化和弱暴雨区不显著粗化与暴雨时雨量分布相关。这些结果表明，粒度分析可以为重建过去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.