黄土中古土壤CaCO3淀积层及其意义

西安东郊黄土中古土壤ＣａＣＯ３和淋滤裂隙等的研究表明，使ＣａＣＯ３发生迁移的水为重力水，ＣａＣＯ３淀积层的顶界代表重力水淋溶亚带的底界，也是重力水发生突变的分界。薄膜水不具淋溶作用，也不会引起ＣａＣＯ３的淀积。由ＣａＣＯ３淀积深度可知，中更新世温湿期降水分配不均，雨季与旱季分明，增加的降水量主要集中在雨季降落；温湿期与冷干期的差别主要在雨季，旱季差异小。

ILLUVIAL CaCO 3 LAYERS OF PALEOSOIL IN LOESS AND ITS ENVIRONMENTAL SIGNIFICANCE

On the basis of the study on the illuvial CaCO 3 layers of paleosoil and leached cracks ,we know that the water by which CaCO 3 is moved is gravity water,and the top boundary of illuvial CaCO 3 layers represents the bottom boundary of leached zone for gravity water and is also abrupt chang boundary of gravity water The water existing in the form of thin film does not possess leaching action and does not give rise to illuviation of CaCO 3 According to the illuvial depth of CaCO 3 the rainfall was not well-distributed during middle Pleistcene,the difference was clear between rain season and dry season,and increased rainfall falled mainly in the rain seasons at that time the difference between the warmmoist period and colddry period exists mainly during raining seasons while difference was small between dry seasons