Environmental Changes In Middle Reaches Of Yi River From The Last Deglaciation To The Middle Holocene

The last deglaciation is a transition period from the last glacial to postglacial, which is different with the slow changes of the last glacial climate. The last deglaciation climate rebound unstable and the temprature was fluctuated changes. Although climate rebounded warming, but there were still Oldest Dryas, Bolling, Older Dryas, Allerod, Younger Dryas climate events which gave the important impact on the global climate. Holocene climatic and environmental changes wre closely related to human survival and development, which had become the focus of research in the past global changes. Although the climate became warmer at the end of the Last Glacial Maximum, the climate was severe tremor, having alternating cold and warm events which had the great reference value to study predict climate and environmental change. Compared with the late Holocene, Early Holocene had less human activity and had the advantage of the natural variability of the climate and environment. Although the mid-Holocene is in the period of Megathermal maximum, cooling events had a significant influence.Yi River basin had given birth to the brilliant Longshan Culture since the Holocene, but the frequent natural disasters and environmental evolution convection had a profound impact on the socio-economic development and ancient culture. Even ancient culture suffering from the environmental catastrophe events had the decline. The study of the ancient culture of Middle Reaches of Yihe River could establish regional paleoenvironmental evolution sequence and also provide reference for predicting the future environmental changes. Through out the data processing and analysis of14C dating, element geochemistry, LOI and particle size of the river sediment of Linyi Small Commodity Market Section in Middle Reaches of Yihe River, we explored the process of environmental change as well as important environmental mutation events in this region, also compared with neighboring regions paleoclimate records. We conclude:(1) The environmental change process of middle reaches of Yihe River from the Last Deglaciation to the Middle Holocene could be broadly divided tinto three stages:①16866～13630cal a B.P. cold and dry climate period;②13630～10440cal a B.P. climate cold and dry quickly;③10440～8672cal a B.P. cold and humid climate with flicker;④8672～6755cal a B.P. warm and humid;⑤6755～5850cal a B.P. climate tend to dry;⑥5850～4698cal a B.P. more warm and humid climate.(2) The values of A12O3and Sr suddenly dropped to the lowest during12577-10440cal a B.P. period. The ratios of SiO2/Al2O3and Sr/Cu and the value of SiO2were becoming high and low respective. The decreases of Md and LOI show that hydrodynamic weakened, reduced precipitation and the climate dries colder appears the Younger Dryas event.(3) The sediment records of Linyi Small Commodity Market Section not only had better contrast with the Subei Basin YZ drilling records but also had good agreement with China Southwest Dongge Cave oxygen isotope records and identify the Younger Dryas event. It provided the establishment of good corroboration to the environmental evolution process of middle Reaches of Yihe River from the last deglaciation to middle Holocene.