关键词: 地层划分, 土壤亮度, CaCO₃含量, 频率磁化率, AMS¹⁴C测年

Abstract: Research on the lithology, chronology and proxies of mid-to late Malan Loess strata at Yuanbao in Linxia of Gansu province showed that the studied section contained one strongly soil-forming layer and 6 weakly soil-forming layers. They reflected climatic events in one interglacial period, 6 interglacial intervals and 7 glacial stages recorded in the Malan Loess. Among them, the 3 palaeosol layers in the middle of the Malan loess section developed in the last interglacial interval. The lower palaeosol matured, which in turn followed by the upper and the middle layer. This showed that even during the warm and wet climatic interglacial period, there also existed difference in temperature and humidity. The Lightness index of soil not only can be used for stratigraphic division but also has a good correlation with CaCO₃ and magnetic susceptibility. Hence, they can be used as reliable and sensitive proxy for the climatic and environmental changes.

Key words: stratum division, soil lightness, CaCO₃content, frequency dependent susceptibility, AMS¹⁴C dating