Study On The Changes Of Palaeoenvironment And Palaeoclimate During The Past 3Ma Recorded In Xinghua Core At Northern Jiangsu Basin

Supported by the NSFC director fund "Research on physiognomy development and the drainage area evolution of Yangtse River basin", for the first time, we have done much research work on long time-scale palaeoenvironmental changes of Eastern China typical monsoon area. The sediment stratum and environment was analyzed and reconstructed by GR curve, granularity index and lithology characterization. By multi-proxy analysis, such as granularity, chroma, carbonate content, susceptibility, sporo-pollen assemblages, etc, we have constructed the palaeoenvironmental change processes during the past 3 Ma of northern Jiangsu basin, and which will provide a foundation for constructing the palaeoenvironmental change sequences of Eastern China since Late Cenozoic.The results of lithology characterization, GR curve and granularity analysis indicate that, the sediment condition in Xinghua has experienced several alternation. The research results are as follows, 350~296.1m, deposit of fluvial-lacustrine alternative facies; 296.1 ~ 254.1m, deposit of lacustrine facies; 254.1~230.1m, deposit of fluvial facies; 230.1m~156.2m, mainly deposit of lacustrine facies, in which there is a short-term deposit of fluvial facies; 156.2m~102.8m, deposit of fluvial-lacustrine alternative facies; 102.8m~48.78m, deposit of lacustrine facies; 48.78m~38.21m, deposit of swamp facies; 38.21m~l1.62m, deposit of lacustrine facies; 11.62m~0m, deposit of lacustrine-swamp facies.Multiple environmental proxies of Xinghua core record the process and characters of palaeoclimate evolution of Northern Jiangsu Basin during the past 3Ma. During the period, the palaeoclimate of Xinghua has experienced several phases, 3.26~2.68Ma, relatively humid period; 2.68~2.32Ma, relatively arid period; 2.32-2.13Ma, relatively humid period; 2.13~1.50Ma, relatively arid period, during which there are some little humid fluctuation; 1.50~1.00Ma, relatively humid period; 1.00~0Ma, humid and arid period alternate frequently, during which at least 6~7 prominent fluctuation gyrations have been recorded.The research results also indicate that, the palaeoclimate of the typical monsoon area in Eastern China has experienced two prominent changes during the past 3 Ma. The period of 2.26-2.16Ma is the transition time of the formation of typical monsoon climate in China. Before this period, the palaeoclimate recorded by sediment had many characters that belong to Savanna. The palaeoclimate had not completely deviated from the Pliocene pattern in many aspects. The typical monsoon climate of high-temperature and high-humidity had not come up in Northern Jiangsu Basin until 2.16Ma. The other change happened in the period of 0.9~OMa, in this period, the difference between ice age and interglacial was obvious and there is prominent process of ice age and interglacial.The arid-humid fluctuations since around 3 Ma disclosed by Xinghua core reveals a strong correlation with the deep-sea oxygen isotope record and loess-plateau record. Particularly, as to the environmental change process since Brunhes, the results not only has great comparability with the wind sediment hi this area, but also has strong accordance with the Northern loess-plateau record and deep sea oxygen isotope record. This indicates that the climate change in Eastern China not only has great regional character, but also has great correlation with the global climate changes.The comparison of climate change in Eastern area since Late Pliocene indicates that, the formation of typical monsoon climate in Eastern area varies with the geographical location. To some extent, the difference shows that, in Early Quaternary, the monsoon that influenced Eastern area was not strong, and the area it affected was very limited. But as the monsoon strengthened and its influenced area enlarged, the monsoon climate finally has influence on the whole Eastern area until the end of Early Pleistocene.The research also indicates that, the climate change in Eastern China has great correlation with the uplift of Tibetan Plateau, the Kuroshio and t...