摘要
选择地处西北半干旱区、又具有代表性的黑木沟标准剖面,逐一测试其土层中的碳酸钙与干容重,进而由相关参数推算各土层的碳酸钙的沉积速率(V,下同),这是笔者的尝试。结果表明,该剖面中的碳酸钙的沉积速率,均有自下而上递增的趋势,各层总平均速率为0.20g/cm^2·10~3a。
The difference of deposition rates of CaCO3 between in loess and paleosol with different ages is found out through the analysis of 276 samples collected from the Hei-mugou standard loess section in Luochuan County. Shaanxi Province, located in dry or semidry areas of Northwest China. The deposition rates of CaCO3 tend to be greater from bottom to ,top as loess gets younger. For example, the deposition rates of CaCO3 in Wucheng loess is 0.09g/cm2@ 103a, 0.29 in the lower part of Lishi loess, 0.36 in the upper part; 0.21 in Malan loess; 0.07 in paleosol of Wucheng loess, 0.21 in the lower part of Lishi loess, 0.19 in the upper part; 0.18 in dark loessal soil of Holocene.The deposition rates of CaCO3 in loess with various ages are all greater than that: in their corresponding paleosol. For example, the deposition rate of CaCO3 in Wucheng, loess is 1.3 times as big as in its paleosol; 1.4 times in the lower part of Lishi loess, and 1.9 times in the upper part.The deposition rates of CaCO3 in loess-paleosol series increase synchronously from bottom to top, and the deposition rates in loess are greater than in their corresponding, paleosol, which coincides with the fact that the paleoclimate during the period of Quaternary turned from warm- humid to dry-cold, and the climate changed alternatively between warm-humid and dry-cold. From above we conclude that the deposition rate of CaCO3 and its variation can be used as a mark to divide Quaternary strata.In order to date unknown strata and to determine the activity period of fault in a certain area, it is of great importance for us to evaluate deposition rate of CaCO3 in dry or semidry areas, to find out empirical parameters and to establish certain models. The aforesaid method of dating with calcic soil is a simple and feasible way of geologic age determination.
出处
《地震地质》
EI
CSCD
北大核心
1989年第1期91-98,共8页
Seismology and Geology
关键词
碳酸钙
地质年代
沉积速率
洛川
Luochuan, Original CaCO_3, Secondary CaCO_3, Deposition rate of CaCO_3, Geologic age
