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对陕西洛川剖面 15 80个黄土样品的粒度数据分析表明 ,黄土的基本粒级 ,即在 2～ 5 0 μm的标度范围内 ,粒度分布具有分形特征。黄土的粒度分维值在 2 16～ 2 5 1之间 ,平均值为 2 32 ;而古土壤的粒度分维值在 2 2 3～ 2 5 1之间 ,平均值为 2 41;粒度分维值对黄土与古土壤的形成环境的演变 ,有良好的指示意义。粒度分维值显示 ,2 5 0万年以来 ,东亚季风不断增强 ,变化周期和变化幅度逐渐变大。在早更新世 ,季风较弱 ,变化周期短 ,变化幅度小 ,表现为 2～ 4万年的周期 ;而在晚更新世 ,季风较强 ,冬季风和夏季风相互消长 ,变化周期长且明显 ,变化幅度大 ,表现出 10万年的变化周期。
Particle size data analysis of 1580 loess samples from the Luochuan section in Shaanxi Province shows that the particle size distribution of the loess has a fractal characteristic in the range of 2 ~ 50 μm. The fractal dimension of loess is between 2 16 and 25 1, with an average of 2 32. The fractal dimension of paleosol is between 2 2 3 and 2 5 1 with an average of 2 41. The value of the formation of loess and paleosol evolution of the environment, a good indicator. The fractal dimension values show that the monsoon of East Asia has been increasing continuously since 25000000 years, and the cycle of its variation and its changing range become larger gradually. In the early Pleistocene, the monsoon was weak, the period of change was short and the change range was small, showing a period of 2 to 40,000 years. In the late Pleistocene, the monsoon was stronger, the winter monsoon and the summer monsoon were longer and longer, and the change period was longer , A wide range of changes, showing a change cycle of 100,000 years.