摘要
根据黄土土壤特征的研究和黄土地层古土壤的识别和划分，结合磁化率测定，研究了黄土剖面冷干与温湿条件下发育的古土壤的分层和代表的气候旋回变化。资料表明，黄土具有土壤的结构和淀积成分，它是在相对冷干气候条件下发育的成熟的灰黄色古土壤，能够可靠地作为冷干气候的指示；２５０万年来的黄土地层至少可分为５１层灰黄色古土壤与５０层红褐色古土壤，代表了５１个生物、气候、土壤旋回和亚旋回的变化。在５０万年来的温湿气候阶段中，气候波动更频繁。
According to the field survey and laboratory analyses of microstructure and susceptibility, the soil character and the climate cycles indicated by paleosol were researched in the paper. Loess has clear soil structure such as granular structure, lumpy structure, similar prismy structure and many holes for plant roots or animal worms. In some layers, there is optically oriented clay film. Secondary CaCO3 is rich in loess and there is some secondary CaSO4 in the northwestern loess. They are all illuvial products of soils after being leached. In general, there is organic matter in loess. Sometimes, it appears in the form of black spots, which suggests that it formed in the soil-forming processes. All of them show that loess has the typical soil character in arid areas or semiarid areas and the formation of the loess is soil-forming processes. The development of the loess is very slow and time is long enough for it to become mature paleosol. Because of the cold and arid climate condition then, it didnt become the red-brown paleosol. Grey-yellow mature soils only could be formed at that time. Loess had been in a stable state and it can be regarded as a reliable indicator for the cold and arid climate. The research material about the climate for soil development and the soil character show that loess is mainly made up of Brown Soils, Sierozems, Chestnut Soils, and Black Loessial Soils which developed in the steppe and woods-steppe areas. On the basis of the replacement of the loess and the red-brown paleosols, we can divide the creature, climate and soil change cycles. There are 50 layer red-brown paleosols indicating warm and wet climate and 51 layer grey-yellow paleosols indicating cold and arid climate in loess strata since 2.50 Ma BP. They are all macrostropic appearance of the creature, climate and soil change for a large range. According to the replacement of these two types of soils, we can divide the environment change since 2.50 Ma BP into 51 cycles and sub-cycles. The difference between cycle and sub-cycle
出处
《中国沙漠》
CSCD
北大核心
2002年第1期11-15,共5页
Journal of Desert Research
基金
国家自然科学基金项目(40071006)
国际地质对比计划项目(IGCP379
IGCP448)
陕西师范大学重点项目(SN
