Modern sedimentation rates and dry-humid change inferred from grain size records in Dianchi Lake, Yunnan Province
Based on radionuclide dating (210Pb and 137Cs) in the sediment core of the Dianchi Lake, Yunnan Province of China, we calculated the sedimentation rates in the past 159years. The vertical profile of 137Cs has three obvious 137Cs peaks in the core corresponding to 1963, 1975 and 1986, since the onset of 137Cs fallout in 1954. Using the dating of the 137Cs peaks, the four time-averaged accumulation rates of the Dianchi Lake were 0. 062,0. 051, 0. 049 and 0. 043 g/cm2 · a-1 , respectively. Four stages with different accumulation rates in core DC1 indicated a slower process since the onset of atmospheric nuclear weapons testing in the 1954. According to the result of 210Pb (CRS) dating in DC1, the sedimentation rate is 0. 052 g/cm2 · a-1 , which is unstable in the past 129 years, which might be related to human activities during different historical periods of the past 100-150years. As for dissimilar physical and chemical associations, diffusion characteristics for the two radionuclides (Ph and Cs), we interpreted the rationality of deviation by the two dating methods. The further precise result can be obtained by combining two or more dating methods, respectively. Compared with the local rainfall in the past 50 years with sediment grain size in the region of Dianchi Lake, it is found that there was an obvious variation trend in the sediment grain size with the fluctuations of rainfall. All these findings indicate that there is a positive correlation between grain size and the fluctuations of rainfall. This shows that sediment grain size could reflect the rainfall changes trend at a short time-scale and high resolution investigations, i.e. larger sediment grain size reflected more rainfall and wetter climate while smaller sediment grain size reflected less rainfall and drier climate.
radionuclide dating (210Pb and 137Cs)sedimentation rategrain sizewet and dry climateDianchi Lake
NETL
NSTL
万方数据
维普
