Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai |
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| Authors: | Hai Xu Bin Liu Feng Wu |
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| Institution: | (1) State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences. Xi'an, 710075, China;(2) Graduate school of Chinese Academy of Sciences, Beijing, 100049, China |
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| Abstract: | The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However,
the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the
spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai.
We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation
rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous
input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal
scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering
and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they
compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary
to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before
it is used as an indicator of weathering intensity of the catchment. |
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