四川盐源盆地的红色土壤及其分类问题的初步探讨

<正> 盐源盆地位于四川省西南隅,广泛分布着红色土壤。以往的文献将这类土壤归为山地红壤,或褐红壤。本文根据最近的调查研究,对其发生分类进行初步探讨。(一)盐源盆地的成土条件盐源盆地属于台缘拗陷,其基本构造轮廓完成于印支运动末期,在第三纪后的新构造运动中,

PROPERTIES AND CLASSIFICATION OF RED—COLORED SOIL OF YANYUAN BASIN IN SICHUAN PROVINCE

In Yanyuan basin in the southwest of Sichuan province, a red-colored soil is distributed widely in the range of 2280—3200 meters above sea level. The soil exhibits red-brown or brown-red colors, and is similar to red earth in many ways. Investigation of five soil profiles derived from various parent materials and situated in different altitudes indicates that the weathering degree of the soil is high, SiO_2AI_2O_3 and SIO_2/R_2O_3 ratios of its clag are 1.6—2.7 and 1.1—2.0, respectively. But the modern bio-climatic condition of the soil is only comparable to that of burozem or yellowo-brown soil in east china, and under this condition such a highly weathered soil could not be formed. Thus, the writers think that it is a unigue derivative from the ancient red soil formed in earlier geological ages. The soil is regarded as a seperate genetic group in classifcation and named Red-Brown Earth since it is different from either the red earth in allitic weathering or the yellow-brown soil derived directly from various parent rocks.