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根据关中平原4个剖面第5层古土壤风化特征的研究得出,该层古土壤风化剖面厚度大,明显超出了土壤发育的厚度,形成了厚2m多的风化淋滤黄土层;第5层古土壤之下的黏土胶膜、风化淋滤黄土层、Fe2O3,CaCO3和元素Sr分布深度指示关中平原该层土壤发育时年平均降水量达到了900余毫米,含水量高的土壤重力水带分布深度至少达到了4.2m,在每年4.2m深度范围土层含水量一般都在20%以上,4.2~5m深度范围内土层含水量也较高,当时土壤水分充足,没有土壤干层形成,适于森林植被发育.该层土壤发育时的年平均降水量显著大于年土壤总蒸发量,水量平衡为明显的正值,大气降水能够正常补给地下水.该层土壤发育的中、晚期土壤水具弱酸性特征.关中平原第5层古土壤发育时为亚热带气候,而且比亚热带北缘的气候更暖湿一些.那时秦岭以南和以北均为亚热带气候,当时秦岭失去了亚热带与温带气候分界线的作用,夏季风活动强度大,能频繁越过秦岭山脉,并给该区带来了丰富的降水,决定了当时土层含水量较高.
According to the paleo-weathering characteristics of the fifth layer of the four sections of the Guanzhong Plain, the paleo-weathering section of this layer has a large thickness, which is obviously beyond the thickness of soil development and forms a weathered and leached loess with a thickness of 2m. The fifth layer The clay film under the ancient soil, the weathered leaching loess layer, the depth distribution of Fe2O3, CaCO3 and elemental Sr indicate that the average annual rainfall of this layer of soil in the Guanzhong Plain reached more than 900 mm, and the soil moisture distribution with high water content Depth of at least 4.2m, soil moisture content of 4.2m depth range each year are generally more than 20%, 4.2 ~ 5m depth range of soil moisture content is also high, when the soil moisture sufficient, no dry soil layer formation, suitable In the development of forest vegetation, the average annual rainfall during soil development was significantly greater than the annual total soil evaporation, the water balance was significantly positive, and the atmospheric precipitation could supply groundwater normally. The paleo-soil of the fifth layer of the Guanzhong Plain was sub-tropical in development and was warmer and wetter than the northern margin of the subtropical climate, when the Qinling Mountains were subtropical to the south and north of the Qinling Mountains, With a temperate climate and the role of the dividing line, the summer monsoon activity intensity, can frequently cross the Qinling Mountains, and to the region brings a wealth of rainfall, high soil moisture content was determined.