CHROMA INDEX RECORD OF CORE XH1 AT NORTHERN JIANGSU BASIN AND THE CLIMATE SINCE MID-PLEISTOCENE

Northern Jiangsu basin lies in the transitional region from ocean to continent and its climate is dominated by the East Asian monsoon system.Reconstructing the evolution history of paleoclimate in this region will provide significant further understanding of the process, rule and evolution trend of the East Asian monsoon. A drilling core XH1 of 350 m at Xinghua in the basin was recovered to reconstruct its environment evolution history. The results show that chroma index of the upper part 90 m of core XH1 responds sensitively to variations of precipitation. It could be used to indicate the intensity of East Asian summer monsoon and the climate changes. The process of climatic evolution since mid-Pleistocene could be divided into 9 major cold-warm fluctuation cycles by researching chroma index record with toc and pollen proxy,which were well corresponding to the record of deep sea and loess, and also had apparent regional features of long-term evolution trend and some stages. Generally,in the middle stage of mid-Pleistocene,climate of northern Jiangsu basin became colder and drier. Range between cold and warm enlarged and last four glacial-interglacial cycles became more distinct.