宣城第四纪红色粘土剖面的发育特征

CHARACTERISTICS OF DEVELOPMENT OF QUATERNARY RED CLAY IN XUANCHENG, ANHUI PROVINCE

宣城第四纪红色粘土14层土体硅铝率、风化淋溶系数，以及阳离子交换量、盐基饱和度和粘粒含量等风化、成土作用指标表明，该剖面各层次之间仅显示出一定程度沉积作用和成土作用的差别。它们是边沉积边成土作用的产物。上覆1m左右厚下蜀黄土，且由均质红土层、铁锰焦斑层和网纹层构成的宣城第四纪红色粘土应归属于埋藏类型古土壤。

A section of Quatemary red clay, located in Xuancheng, Anhui province, is recognized a typical and good one for the study of red paleosols in the southern part of China. It was divided in earlier studies into 14 layers (7 formations) except a gravel formation in the bottom. Each formation consists of a 'red layer' ('red paleosol') and underlying 'brown-yellow layer'('deposit'). To elucidate its characteristics of development main chendcal and physical propenies for 14 layers of the section were analyzed.The results indicated that the silica content in each 'red layer' was not always less than that in the underlying 'brown-yellow layer', and the contents of aluminum and clay in each of the 'red paleosols' were not more than those in the corresponding 'sedimentary layer', respectively. In the same way, other research data also had analogous phenomena. Based on the indexes of weathering and soil formation, including silica-aluminum ratio, indexes of weathering and leaching, cahon exchange capacity,base saturation, as well as the clay content we conclude that there were no regular cycles between soil formation of 'red layer' and deposition of 'brownyellow layer' in the section. In fact each layer of the 'red paleosols' didn' t develop from the underiying 'brown-yellow sedimentary layer'. Each of the 14 layers within the profile only to certain extent showed its difference of deposition and soil formation. Moreover,pedogenesis was sometimes weaker, sometimes stronger than the sedimentation. On the basis of these characteristics, the authors think that these are buried red paleosols,which consist of uniform red soil, iron-manganese illuvial, plinthitic horizons, and overlain by a yellow-brown horizon derived from the Xiashu Loess.