Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai

摘要

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, weinvestigated the spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surfacesediments of Lake Qinghai. We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates wellwith that of the mass accumulation rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporalvariations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest thatRb/Sr ratios of the surface sediments are closely related to terrigenous input from the catchment. Two out of eightcores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the othercores do not show such relationship. The result of this study suggests that physical weathering and chemicalweathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and theycompete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it isnecessary 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.