• 论文 •

### 西安刘家坡剖面第1第5层古土壤研究*

1. 西安地质学院
• 收稿日期:1990-04-20 修回日期:1991-06-12 出版日期:1991-12-15 发布日期:1991-12-15
• 基金资助:
*国家自然科学基金;中国科学院西安黄土与第四纪地质研究室资助项目

### A STUDY ON THE FIRST AND THE FIFTH PALEOSOLS IN LIUJIAPO SECTION IN XI'AN

Zhao Jingbo

1. Xi'an College of Geology
• Received:1990-04-20 Revised:1991-06-12 Online:1991-12-15 Published:1991-12-15

Abstract: We have studied the structure, illuvial depth of CaCO3, sporo-pollen and chemical composition of the first and the fifth paleosol. The materials indicate that the first paleosol is Burozems which developed under the vegetation of deciduous broadleaf trees, and mean annual temperature was between 8℃ and 12℃ and mean annual rainfall was more than 800 mm at that time. The fifth paleosol is Yellow-brown Earth and the vegetation was of the characteristics of north substropical broadleaf trees when the paleosol developed, and the mean annual temperature was above 15℃ and the mean annual rainfall was more than 850 mm at that time.The illuvial layer of CaCO3 of the two paleosols does not contact closely with the bottom of the paleosol and occurs in the lower loess more than two mere-rs in depth under the bottom of the paleosol, which is noncontinuous illuvial layer of CaCO3 of the paleosol. This illuvial layer of CaCO3 shows that the rainfall was rich enough for leaching out all CaCO3 of paleosol and the paleosols was in neutral or acid condition. Because noncontinuous illuvial layers can not be put under the component part of soil, the first and the fifth paleosol are not of illuvial layer of CaCO3 in Liu jiapo section and their section formation is not Bt-Bk-C of drab soils. The first paleosol is of the characteristics of Burozems, there fore, its section formation is Bt-C (A layer had been resolved).R2O3 in the fifth paleosol moved down for a distance over one meter and is more than that of north subtropical yellow-brown Earth in sihong area of Jiangsu province and approximate to that of yellow-brown Earth in Liuhe area to the south of sihong area. R2O3 illuviated obviously in lower fart of the fifth paleosol, hence, its section formation is Bts-C of yellow-brown Earth (A layer had been resolved).Since the rainfall was rich during the development of the first and the fifth paleosol and the depth affected by weathering was great and exceed.the thickness of soils, the paleosols had become weathered crusts that consist of upper paleosol and lower loess in which weathered cracks developed well.