安徽宣州黄棕色土和第四纪红土的比较研究及其古气候意义

COMPARATIVE STUDY OF YELLOW-BROWN EARTH AND QUATERNARY RED CLAY IN XUANZHOU,ANHUI PROVINCE AND ITS PALAEO-CLIMATE SIGNIFICANCE

通过地貌和典型剖面的考察和研究，发现安徽宣州地区黄棕色土的层序位于第四纪红土层之上。用ESR测年法测得黄棕色土年龄约为80kaB．P.，红土年龄约为240kaB．P.。对这两种成土母质的各项理化性状和磁化率指标进行比较研究，发现黄棕色土受风化作用的程度不如第四纪红土。这表明该地区24万年前的湿热气候至8万年左右开始转凉，不适于红土的形成。现今该地区出露的红土都是中更新时期古气候的产物，而黄棕色土则是与近代气候环境更相接近的一种沉积物。

Quaternary red clay and yellow--brown earth coexist in Xuanzhou, Anhui Province. The former is mainly distributed on eroded hills and slopes, the latter mainly on plain, low hills, valleys and feet of hills. According to the investigations of topographical features and typical soil profiles in this region, it was found that the yellow--brown earth horizon was above the Quaternary red clay horizon. With ESR dating method, the yellow--brown earth was dated to 80 ka B.P., while the Quaternary red clay was 240 ka. B. P Comparative study of basic physical and chemical properties and susceptibility of the two soil-forming parent materials showed that the Quaternary red clay suffered stronger weathering than the yellow--brown earth. It indicated a hot and humid climate in the middle Pleistocence, when the Quaternary red clay was formed, and then the climate turned cold in the late Pleistocence. This change resulted in the halt of red earth development and the formation of yellow--brown earth. The red weathering mantle exposed in this region was considered to be formed under the palaeo-climate in the middle Pleistocence; while the yellow--brown earth was mainly affected by the modem climate.