Abstract
We present radiometric data from nine lakes across the Tibetan Plateau, and compare their reliability in relation to recent research. Unsupported 210Pb profiles show, except for one particular lake, non-exponential decline of 210Pb activity with sediment depth. Stratigraphic dates based on global atmospheric nuclear weapons maximum fallout of 137Cs (1963) support the use of the constant rate of 210Pb supply (CRS) model in four of the dated cores. The discrepancy in the others is likely due to recent increased input of catchment-derived 210Pb. 210Pb dates in this study suggest that post depositional diffusion of 137Cs activity has been significant. The practice of assigning early 1950s dates (start of global atmospheric thermonuclear testing) to lake sediment sequences on the Tibetan Plateau should be used with caution. 137Cs profiles from Tibetan lake sediment cores and their geographical distribution suggest that 137Cs derived from the 1986 Chernobyl accident or atmospheric testing in China was not sufficient to form a significant peak effective for dating.
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