关键词: 西拉木伦河, 全新世大暖期, 史前考古文化, 地貌背景

Abstract: The Xar Moron River Basin is located in the interlock area of farming and pasturing, Northern China, where the present climate is semi arid, and the ecosystem is very sensitive to climatic changes and human activities. Based on geomorphologic observations and archeological excavations, the authors analyzed the relationship between geomorphic evolution and prehistoric cultural development during the Megathermal in Xar Moron River Basin.
The main geomorphologic processes were loess sedimentation, gully aggravation, degradation, deserts spreading and retreating during the Megathermal in this area. This had exerted important influences on the changes of prehistoric cultures in the Xar Moron River Basin.
The Xinglongwa Culture （8000～6500aBP）, which is characterized by hunting and collecting, and the Xiajiadian Upper Layer Culture （3300～2800aBP）, which is characterized by Animal husbandry, can be discovered in the whole Xar Moron River Basin. Since loess is beneficial to agriculture, the Zhaobaogou Culture （6500～6000aBP）, Hongshan Culture （6000～5000 aBP） and Xiajiadian Lower Layer Culture （4000～3300aBP）, which have characteristics mostly in agricultural cultures, are found only in the Loess region.
There is a close relationship between alluvial landforms and localities of culture sites. Human changed habitats along with gully degradations. The Xinglongwa Zhaobaogou sites are located on the loess tablelands. The Hongshan sites are distributed on the loess tablelands and are discovered in the sediments of the second terraces of the Xar Moron River. The Xiajiadian sites are on the surface of the loess tablelands and the second terraces, the relics of the sites also can be discovered in the sediments of the first terraces. The Liao Dynasty sites are on the surface of the first terrace.The climate changes during the Holocene resulted in the spreading and retreating of deserts in this area, causing the rise and fall of prehistoric cultures. The first expansions of desert （5000～4000aBP） resulted in the fall of Hongshan culture. The second desert expansion （3300～2800aBP） caused the transition from agricultural culture of Xiajiadian Lower Layer to nomadic culture of Xiajiadian Upper Layer.

Key words: geomorphic evolution, prehistoric culture, the Megathermal