Soil characteristics and new formation model of loess on the Chinese Loess Plateau

In this paper characteristics of loess are discussed from a pedological perspective. A new model of loess formation is presented, developed in different soil formation processes according to its pedogenic characteristics, including soil structure, organic matter content and CaCO3 content. Loess has all the characteristics of typical soils and all five soil-forming factors have important roles in loess formation. In this regard, loess is a type soil and the previous concept of loess actually comprises various kinds of palaeosols developed in cold and arid climatic conditions. The loess-forming process is, in fact, equivalent to a pedogenic process and loess layers with different characteristics represent different pedogenic processes indicative of different environments, such as desert-steppe, steppe or forest-steppe climatic conditions. In contrast to red-brown palaeosol layers, which develop in warm and wet climates, loesses–more accurately called ‘loessial palaeosols’–are grey-yellow palaeosols and can be regarded as a reliable indicator of cold and arid climate. The model of loess formation suggests that aeolian dust transfers to grey-yellow palaeosols via pedogenesis and the characteristics of loess are mainly a result of climatic conditions and diagenesis processes after its sedimentation. This new model of loess formation also suggests that traditional pedological theory has its limitations when explaining soil formation processes.