The Essence and Formation Model of the Loess
ZHAO Jing-bo (Department of Geography, Shannxi Normal University, Xi'an 710062) (State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment,CAS, Xi'an 710075)
The materials show that the loess possess bio-texture, edg-prismatic and crumb texture, and also have the illuvial component of CaCO 3 coming from the soil and the atmospheric water, which reveals the reason of high CaCO 3 content and calcification.In the cold and wet areas, the organic content in the loess is higher than that in the soils of desert-grasslands areas, which indicate the loess is the soils with the organic substance formed during the soil-forming process. The loess possess these conditions such as biology, climate ,fine-homogeneous parent material forming soil fast., available terrain and long enough time to change into mature soil during its the developmental process, which shows during the loess formation process, the five fundamental factors for soil-forming have been provided .In essence, the loess is soil, and it is made up of multiple gray-yellow paleosol developed under the conditions of cold and arid climate relatively. In addition, it is steady and mature paleosol under the unique climate condition at that time, the soil types of which are mainly chestnut soil, sierozem, brown soil and dark loessial soil but only minority is cinnamon soil. The formation model of the loess is the one that wind dust experience soil-forming processes in the areas of forest-grasslands, grasslands and desert-grasslands. The loess can indicate the cold and arid climate. In the loess plateau areas, the soil resource enriches mostly, the loess is the soil resource with superior soil texture, rich element and mineral component. The sub-divisions of soil profile isn't obvious owing to continue deposit of wind dust and the weak soil-forming processes. The physical and mechanical character of the loess is influenced by the soil-forming process to a great extent.