多年冻土上限是冻土剖面中的一个特殊物理分界面。当上限稳定时间较长时,冻土剖面中发生的某些过程就会以上限为界而出现显著的差异。反之,找到这些差异的突变位置就有可能确定古代冻土上限的深度,从而研究冻土发育历史。 笔者就是试图从冻土剖面中粘土矿物相对含量变化来进行古代冻土上限的判断。 一、分析方法 主要是X-射线衍射分析,部分用差热 Permafrost caps are a special physical interface in permafrost profiles. When the upper stability time is longer, some processes occurring in the frozen soil profile will be significantly different from the upper limit. On the contrary, finding the location of the mutation in these differences makes it possible to determine the depth of the ancient permafrost so as to study the history of frozen soil development. The author attempts to judge the upper limit of the ancient frozen soil from the change of the relative content of clay minerals in the frozen soil profile. First, the analytical method is mainly X-ray diffraction analysis, some with poor heat