Environmental changes during early-middle Holocene from the sediment record of the Chaohu Lake, Anhui Province.

A typical lake sediment core is obtained from the Chaohu Lake in the lower reaches of the Yangtze River, Anhui Province, China. The timing scale is constrained by AMS 14C dating method. Climate proxies such as pollen and grain size in the core are analyzed to reconstruct the environment changes at this site approximately between 9870 and 2170 cal. a BR The results indicate that at the research area, the climate in the early-middle Holocene had evolved through 3 stages. From 9870 to 6040 cal. a BP, proxy records show a warm and dry climate with low water levels after the late-glacial period. During this stage, cool and dry events occurred at about 8910 and 6060-6030 cal. a BP. Then, between 6040 and 4860 cal. a BP, the climate was humid and vegetation was more flourishing in the Chaohu Lake Valley. The Holocene Optimum occurred at 5840-5500 cal. a BP in the Chaohu Lake, showing the best condition of water and heat. Elm Decline occurred at the period of 5380-4930 cal. a BP. Since 4860 cal. a BP, the climate was warm and dry through 2170 cal. a BP as shown in both pollen spectrum and grain-size histories. Two obvious dry events occurred in 3760 and 2170 cal. a BP, respectively. At 2170 cal. a BP, the water level of the Chaohu Lake reached the lowest as the lakebed possibly exposed. Such lake sediment observations are consistent with the historical records in this area. [ABSTRACT FROM AUTHOR]