从沉积物特征谈太湖的演变

通过太湖湖底淤泥层中的微体古生物及其物理化学分析,在西太潮W1孔发现多门类海相化石。海相化石出现的时间约在1100—5000aB.P.之间。据此提出西太湖在全新世期间曾遭受海侵,因而支持了太湖形成于泻湖的说法,同时,还提出海水进入太湖的时间,比以往学者推测的早2000多年。

Evolution in Taihu Lake ecosysttem as evidence of changes in sediment profiles

Taihu Lake , one of the five largest freshwater lakes in China, is situated in the middle of the Yangtze River Delta, which is inhabited by more than 100 million people and provides one seventh of China's Gross National Product. Marine and brackish organisms found at the bottom (275cm, about 11280 a B. P. ) of the sediment core indicates that sea water intruded to the lowland areas and river valleys of the present western Taihu Lake during the last major rise in sea level. The sea water intrusion to Taihu Lake occured 2000 years ago earlier than previously indicated. Evidence also shows that sea water intrusion was limited , affecting only a part of the present Taihu Lake .Evidence from the lake sediment analysis suggests that this lake underwent major changes from a brackish to a freshwater environment between 5000 and 5300 a B. P. Major changes in sediment were noted between 35 ?45cm ( 5070?5330 a B. P. ) reflecting a period during which inorganic carbon was drastically reduced, primary production (Chl.a and pigments) increased significantly, and many marine and brackish organisms disappeared and were replaced by freshwater forms- This evidence indicates that prior to 45cm , Taihu Lake received constant inputs of sea water, and perhaps existed as a bay or an estuary. After that period, the water gradually became fresh. At depths above 35cm, Taihu Lake turned completed lacustrian under increasing impact of wind-driven lake currents, and expanded substantially to reach its present size. This lake was oligotrophic, the eutrophic conditions in the present lake developed during recent decades as a result of increased nutrient loadings.