A 14 000-year record of paleoenvironmental change in the western basin of China's third largest lake, Lake Taihu

The longest vertical profile from the western basin of Taihu Lake ever take n was nearly 4 m (396 cm) in length and represented a time period of over 1 4 000 years. The core was analyzed for the following proxies, magnetic susc eptibility, organic carbon isotope, total organic carbon, total nitrogen, t otal pigments, saturated hydrocarbons, carbon 14, thermolytic hydrogen (the hydrogen index, HI) and foraminifera. Results from the west Taihu lake cor e indicate that ca. 14 300-13 400 a B.P., the lake was relatively shallow a nd the climate was likely to have been quite arid. From 13 400 to 12 400 a B.P., the environment became less arid and the depth of the water in Lake T aihu increased. Marine incursions occurred during this period as indicated by the presence of numerous marine foraminifera. From ca. 12 400 to 10 900 a B.P., the climate became wetter, warmer and more variable. A cold dry per iod occurred around ca. 11 500 a B.P., causing the lake to become more shal low. From 10 900 to 10 000 a B.P., a warm and wet period reasserted itself and water depth again increased. A cold dry period reoccurred from 10 000 t o 9500 a B. P. From 9500 to 7200 a B.P., the climate was quite variable. By 7200-5700 a B.P., the climate again turned warmer and wetter. Some of the major sediment proxies used in this study changed dramatically at ca. 5050 a B.P., reflecting changes in material source and a probable interruption o f sedimentation. The modern environment (4900 aB.P.-present) was characteri zed by a well oxidized sediment layer and thriving algae. The lake is prese ntly very eutrophic and is characterized by cyanobacteria, primarily Microc ystis aeruginosa, the dominant primary producer in the lake. This is the fi rst study to use a variety of organic geochemical proxies to infer paleoenv ironmental changes in Taihu Lake.