中文摘要：

中国南方第四纪红粘土的成因尚有洪积、冲积、风成、坡麓堆积风化等多种说法。中亚热带5个红土沉积剖面的粒度组成分析结果表明：（1）5个红土沉积剖面的粒度组成表现出较好的一致性，粉砂（4～63μm）为优势粒组，其含量的平均值为48．12％～68．89％，粘粒（〈4μm）含量平均值变化于23．83％～50．10％，砂（〉63μm）含量平均值〈5％。推测中亚热带红土母质具风成特性，沉积后经历了较强的风化成壤过程。（2）粒度参数高度相关，频率曲线以双峰为主体，概率累积曲线表现为三段式和五段式，表明中亚热带各地红土的沉积环境较为一致，但分选具一定复杂性。（3）在剖面上，红土粒度分布随时间变化而变化，棕黄色层的平均粒径值较均质红土层和网纹红土层粗，粉砂含量较高。

英文摘要：

There are different opinions on origin problem of the red earth in the Pleistocene, namely diluvium, alluvium, aeolian, and so on. Based on the grain-size analysis of five representative sections from the mid-subtropics, deposit-environment of the red earth is discussed in this paper. The results show that： （ 1 ） Grain-size distributions of five red earth sections in mid-subtropics are very similar,which probably indicates aeolian characteristics from their parent materials and the weathering process. The average content of 4-63 μm particle group ranges from 48.12% to 68.89%, the one less than 41a,rn and the one over 63μm are respectively from 23.83% to 50.10% and less than 5%. Generally speaking , the grain-size frequency curves of the red earth show the double-peak mode--the 10-63μm paticle group is ＂the dominated mode＂, and the one less than 41aan is ＂the secondary mode＂ or ＂the dominated mode＂ of some samples. （2） The particle parameters are highly correlation, which suggests that the sedimental environment of brown-yellow unit, typical red clay unit and vermiculated red earth unit are similar. However, the probability accumulation curves of red earth could be divided into two types-three-segment pattern or five-segment pattern, which maybe show the more complicated sorting-environment. （3） Mean grain-size value and content of 4-63μm particle group of brown-yellow unit are larger than those of typical red clay unit and vermiculated red earth unit.