中文摘要：

朝阳地区古土壤广泛分布，正确的认识该区古土壤的成因有助于我们进一步探讨该区的古气候变化。本文对辽宁省朝阳市凤凰山古土壤剖面进行系统地粒度分析，并结合剖面形态特征，对该剖面各层次进行成因探讨。研究结果表明：凤凰山剖面上部含有砾石，粗粒组分含量较高，且垂向变化均较大，分选性较差，但同时颗粒组成仍以风成沉积的两个主要粒级为主，为经流水作用改造的次生黄土。剖面下部粒度细小而均匀，砂粒含量低，风尘“基本粒组”相对富集，平均含量在60％～70％之间，各粒度指标均与典型的风成古土壤序列的相近，表现出明显的风成沉积特征。在上、下两部分之间，存在较薄的一个过渡层次。颜色上与剖面下部土层相近，但粒度特征与剖面上部土层相近。

英文摘要：

Paleosol is widespread in Chaoyang, Liaoning Province. A correct understanding of its origin will help us further interpret the variation of palaeo-climate. Based on the grain-size analysis and morphological features description of the paleosol section at Fenghuang Mountain, Chaoyang, Liaoning Province, the material origin of its layers was discussed in this paper. The results showed that the upper section of the profile contains more coarse fractions and loessic fractions, with the presence of gravels, showing vertical changes in grain size. All of these suggested that the upper section is loessic material deposited by water. The lower section has the same morphological features and grain-size features as the typical aeolian loess-paleosol depos- its, which are generally fine and uniform, with low contents of sand, and high contents of the basic fraction of dust, mostly 60%-70%. Between the upper unit and the lower unit, there is a thin mid-shaft. Its color is the same as that of the lower unit, but the grain-size features are the same as those of the upper unit.