Environmetal-Climatic Changes Of Chengdu Plain From 4ka And It's Influence On Ancient Shu Civilization

It is helpful to apply the environmental analyses to paleoenvironmental and paleoclimatic reconstruction. Environmental archeology becomes more and more important, especially in the Quaternary researches. Ancient Shu civilization, as important part of Chinese civilization, attracts people's attention all over the world, with archeology developing and many ancient sites of Shu civilization discovered. Jinsha site, which was discovered in 2001, is the greatest discovery in early 21st century in China.In the research, analyses of grain size, magnetic susceptibility and spore-pollen are used to reconstruct the paleoenvironment and paleoclimate of Jinsha site 4000aBP. Based on the analyses, the relationship between environment and ancient Shu civilization is discussed. In the research, we draw the conclusions as followings:â‘ Based on the analyses of spore-pollen, oryza pollens are discovered at the bottom of the profile. We can conclude that the plant activities began as early as 3800aBP in Chengdu plain, according toδ¹⁴C age determination.â‘¡In the light of analyses of field survey and grain size, the sedimentary environment experienced three phrases: It was alluvial fan and gravels before 3800aBP; Then peat and fluvial environment were deposited between 3800～3300aBP; At last, paleosol prevailed from 3300aBP and small fen peats developed in parts of areas.â‘¢In terms of analyses of spore-pollen, magnetic susceptibility, the climate of Chengdu plain of recent 4000 years was not stable. It was relatively warmer, then declined from 3100aBP, and rose again from 1700aBP but lower than that before 3100aBE It decreased obviously and lasted for a long time, until early 19th, became warm gradually. 7 plant zones and corresponding 7 climatic phrases are concluded.â‘£According to the analyses above, it was usually flood in Chengdu plain before 3000aBP because of wet and rain. But the temperature and precipitation declined since then. The climatic changes led to Sanxingdui civilization decline, to ancient Shu civilization migration from Jian river basin to Min river basin, to twelve bridge civilization prosperity gradually.