Abstract: Soil-forming factors are involved in original rocks, climate, living things, topography and time. If we wish to ascertain accurately the soil-forming time, all remaining factors must be be kept constant. The physical parameters of any soil are related to time. The authors have established a regression equation and correlation coefficients between characteristic parameters and formation time of soil layer B_ms on the alluvial fan in Heyuan area, Guangdong. The age of third-step alluvial fan has been determined by using growth rate of secondary minerals. A chronosequence cf the soil development of the alluvial fan has been set up in Heyuan area, Guangdong.

Key words: Alluvial fan, Werthering soil, Characteristic parameters, Secondary minerals, Guangdong

摘要： 土壤是母岩、气候、生物、地形和时间等综合作用的产物,在其它因素相同的条件下,显示土壤特性的物理化学参数均随着风化时间的增长而有规律的变化。本文初步建立了河源断裂山前地带三级冲积扇中B_ms层土壤的pH值、容重、有机质、次生粘土和三水铝石等与冲积扇形成年龄的关系,并依据次生粘土与三水铝石的增长速率对第Ⅲ级冲积扇的形成年龄进行了计算,初步确定了三级冲积扇形成的年代序列。

关键词: 冲积扇, 土壤风化, 土壤特性参数, 次生矿物, 广东