临夏塬堡黄土剖面中晚马兰黄土地层划分和形成时代

通过对位于黄土高原西部区临夏塬堡中晚马兰黄土剖面地层岩性、代用指标及地层年代学的分析研究．认为该研究剖面存在1个强成壤层和6个弱成壤层．记录了1个间冰期6个间冰段和7个冰段事件。其中马兰黄土中部3层古土壤是末次冰期间冰段的记录，尤以下层古土壤发育最好，上层次之，中部古土壤的发育介于二者之间，表明即便是气候较温湿的间冰段．其气候的温湿程度也是有差异的。色度指标中的亮度不仅可参与地层划分．与CaCOx、频率磁化率有很好的相关关系，而且是一个可靠的、更为敏感的气候环境变化代用指标。

Stratum Division and Age Dating of the Mid- to Late Malan Loess in Yuanbao Section,Linxia of Gansu Province

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 CaCO_(3) and magnetic susceptibility. Hence, they can be used as reliable and sensitive proxy for the climatic and environmental changes.