河西走廊榆木山前土壤发育特征及其随时间(年代)的演变关系

SOIL DEVELOPMENT PROPERTIES AND THEIR EVOLUTION WITH TIME (AGE) IN THE FORELAND REGION OF THE YUMUSHAN MOUNTAINS OF HEXI CORRIDOR

在河西走廊榆木山前开展了旨在用于活动构造测年工作的土壤发育年代学方法的研究。通过在不同时代河流阶地上开挖土壤探槽、系统采集土壤样品并进行化学成分分析，以及对各级河流阶地形成年代的１４Ｃ和热释光年龄测定，详细研究了本区与断层新活动有关的土壤发育的主要物理和化学特性及其随时间（年代）的演变规律，初步建立起了土壤ＣａＣＯ３含量和ＣａＣＯ３累积指数与发育年代的定量计算关系式。经回检和对比分析认为，所建定量计算关系式可试用于同类地区活动断层的测年工作。

In this paper, the primary physical and chemical characteristics of the soil development related to Quaternary faults in the foreland region of the Yumushan mountains of the Hexi corridor, and their evolution with age have been investigated and analyzed. In six well drained soils formed in loess and alluvial proluvial parent materials of various ages (their formation ages are 5 000 to 38 000a ago) in this region, calcium carbonate content obviously increases with age, and so does calcium carbonate accumulation index value which represents the degree of calcic accumulation horizon development in the soil profiles. The data of the ages, the calcium carbonate contents and calcium carbonate accumlation index values of these six soil profiles were used to derive four regression equations as follows: for CaCO 3 content: Y=-37.36+3.254X(1) and for CaCO 3 accmulation index: Y=-7.19+0.298X(2) Y=-91.689+58.01 log X(3) log Y=-1.748+1.545 log X(4)Where Y is the age in 10 3 years, and X is the calcium carbonate content or its accumulation index value. Test and comparative analysis indicate that the three equation (1),(2) and (4) of the above four equations fit best to the data of the study region, and their coefficients of correlation are 0.997, 0.998 and 0.992, respectively. These three quantitative relational expressions can be used tentatively in practical dating work of active faults.