RECORD OF PALEOENVIRONMENTAL EVOLUTION OF TAIHU LAKE IN THE PAST 14000 YEARS

From the analysis of the magnetic susceptibility,TOC,TN,pigment,organic carbon isotope,HI,saturated hydrocarbon and ¹⁴C dating etc.of the sediment samples from cores of two boreholes in the Taihu lake,a knowledge of the evolution of paleoenvironment of the lake during the last 14ka is achieved.The results show that the lake has undergone the following stages:The Lake was at a low level,or even became exposed during 14.3-13.3kaBP,reflecting an arid climate.There existed a transitional stage during 13.3-12.4kaBP,the climate being slightly warm and wet.There are indications of a cold and dry climate around 11.5kaBP,probably corresponding to the Younger Drays event,comparable with other areas in east China.10.9-10kaBP is obviously a warm period with a reducing environment and relatively deep water.There was a alternation of cool and warm climate during 10-7.2kaBP.It was warm and wet during 7.2-5.737kaBP.Many climate indicators changed suddenly in 5.05kaBP,probably a reflection of change in material source and a sedimentation break.The uppermost surficial sediment shows features of a modern environment.The West Taihu Lake is of algae-type with high production and high eutrophication and is characterized by oxidation environment and flourishing algae.The East Taihu Lake is of macrophyte-type with low production and low eutrophication where the organic material mainly came from the exuberant aquatic vascular plants.