【摘要】 本文确定了黄土中古土壤有四种双层淀积类型。第一和第二种是由两层ＣａＣＯ３结核构成的，第三种是由ＣａＣＯ３和ＣａＳＯ４构成的，第四种是由ＣａＣＯ３与Ａｌ２Ｏ３、Ｆｅ２Ｏ３构成的。根据ＣａＣＯ３淀积层成因分析得知，西安附近第一层古土壤具二元发生特点。该层古土壤上部的ＣａＣＯ３淀积层代表碱性土壤发育时期。下部的ＣａＣＯ３淀积层代表中酸性土壤发育时期。因为有些古土壤发育时出现过气候变化，所以具ＣａＣＯ３淀积层的古土壤不一定是碱性的。具ＣａＣＯ３与Ｆｅ２Ｏ３·Ａｌ２Ｏ３构成的双层淀积是酸性土壤的标志。更多还原

【Abstract】 On the basis of the materials in chemical analysis and investigating in field, 4 kinds of 2 illuvial layers have been asertained in this paper. First and second kinds of 2 illuvial layers consists of 2 layers of CaCO3 concretion, third kind of 2 illuvial layers of CaCO3 and CaSO4, fourth kind of 2 illuvial layers of CaCO3, Al2O3 and Fe2O3. By the analysis of CaCO3 in origing, we know that 2 period of soilforming occured during the developing of third paleosoil near Xi’an. Upper CaCO3 concretion layer indicates the developmental period of alkaline soil and lower CaCO3 concretion layer indicates the developmental period of acid soil. It is not certain that the soils with illuvial layer of CaCO3 are alkaline and may become into neutral or acid soil; 2 illuvial layers consisting of CaCO3, Fe2O3 and Al2O3 are a characteristics of acid soils.更多还原