Variations of monsoonal precipitation over the last 16,000 years in the eastern Nanling Mountains, South China

A 350-cm-long sediment core was recovered from Dahu Swamp in the eastern Nanling Mountains in south China for paleoclimatic investigation. Twelve C-14 dates determined on organic-rich bulk samples establish a chronological sequence for this core and yield a bottom age of similar to 16,000 cal years BP. Multiproxies including dry bulk density, magnetic susceptibility, organic carbon isotope, median grain size, silt-size fraction and total organic matter content were used to study variations of precipitation in relation to the East Asian monsoon. The core sediments are characterized by shifts between the lacustrine sediments and marshy sediments, implying hydrological variations between expansion and shrinkage of the water body in the swamp, and suggesting relatively wetter and drier conditions, respectively. Two relatively wetter episodes lasting from similar to 15,000 to 14,000 cal years BP and from similar to 13,500 to 12,800 cal years BP were revealed, possibly corresponding to the Bolling and the Allerod warming events, and three relatively drier phases occurred between similar to 16,000 and 15,000 cal years BP, between similar to 14,000 and 13,500 cal years BP and between similar to 12,800 and 11,500 cal years BP. The three events synchronize with the Oldest Dryas, the Older Dryas and the Younger Dryas cooling events, respectively. A distinctly humid period lasted from similar to 10,000 to 6,000 cal years BP in the early- and mid- Holocene was interpreted as the Holocene Optimum period. Several short dry events were revealed, including the most pronounced one at similar to 8,100 cal years BP that coincides with the "8,200 year" cooling event. Multiproxies indicate an evidently dry climate prevailing in the mid-Holocene (from similar to 6,000 to 3,000 cal years BP), reflecting a weakening of the East Asian summer monsoon. The general trend of Holocene climate shows agreement with the 25A degrees N summer solar insolation, suggesting that the orbitally induced insolation have played a key role in the Holocene climate in south China.