Study On Ancient Environment Of Archaeological Sites In Zhongxian And Wushan By Yangtze River

With the research on global change, the relationship between the development of civilization and the evolution of natural geographical environment has become a focus in the scientific field. It is universally acknowledged that the evolution of geographical environment is one of the main factors, which influences the man-land relationship. The integration of archaeological sites and natural formations plays a key role in restoring the historic environment, exploring the environmental evolution as well as elaborating the relationship between geographical environment and the formation of man-land and its characteristics. At the same time, it is efficient in studying the response of regional cultural development to global change.Located in the transitional zone of the Qinghai-Tibet plateau and the middle-lower Yangtze plain, Chongqing is influenced by south-west monsoon and East Asia monsoon, which results in its sensitivity to climate change. It is also an important area of the birth and development of Chinese civilization. It is of great significance to do environmental archaeology research in this area to explore the responses of environmental evolution and the relation between man-land transference to the global change. This paper probed into the relationship between human - land and environment evolution by analyzing grain-size,magnetic susceptibility and pollen assemblage which stemmed from Ganzhe hill site and Big Cave site samples. Comparative study will also be carried out between other archaeological sites and natural accumulations to explore the mechanism response of relationship between human - land to global change.The results of pollens and magnetic susceptibility showed that the climate of Ganzhe hill site was warmer in Shang dynasty, so it was suitable for ancestors to survive. During Tang and Song Dynasties, climate became cooler and more humid and agriculture civilization was produced in the middle of Tang Dynasty. In Ming and Qing Dynasties, it witnessed an advanced development. The climate went through three stages: warm and wet --cold and dry -- temperature rise, humidity increase during the end glacial period of the late Pleistocene in Big Cave site. Ganzhe hill site is situated in the first terrace of Yangtze River. The results of grain-size showed that this area experienced frequent flood during Historical period, however, its effect on regional cultural development was not that apparent. According to the variation characteristics of grain-size in Big Cave site, it is reasonable to conclude that deposition of this site was mainly the fluvial deposits, however, its effect on regional cultural development is not that apparent。In the depth of 950-720cm, there were some secondary deposits because of ancient human activity. At the depth of 720-320cm, there was mainly flood deposits .At the depth of 320-100cm, there were mainly flood deposits, accompanied by the outbreak of debris flow.Based on the comparisons between other archaeological sites and natural accumulations, it was easily found that the prosperity period of civilization had been mostly occurred in cool and humid climate in this area which was corresponded to the period when winter-monsoon abate and effective humidity increase. The alternative action of South-west monsoon and East Asian monsoon had a massive influence on environment change in Big Cave site in different geological epoch. The environment change had some relation with air-sea interactions in a the low-latitude tropical ocean and the relation with a high-altitude atmospheric circulation.