Carbon isotopes in surface-sediment carbonates of modern Lake Qinghai (Qinghai-Tibet Plateau): Implications for lake evolution in arid areas

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• 作者：Xiangzhong Li^a ; Weiguo Liu^a ; ^b ; ^{liuwg@loess.llqg.ac.cn} ; Liming Xu^c
• 关键词：Carbon isotopes ; Ostracods ; Bulk carbonate ; Fine-grained carbonates ; Dissolved inorganic carbon ; Lake Qinghai
• 刊名：Chemical Geology
• 出版年：2012
• 期刊代码：12_00092541
• 类别：ear
• 出版时间：18 March, 2012
• 卷：300-301
• 期：Complete
• 页码：88-96
• 文件大小：972 K

摘要

To further investigate the significance of carbon isotopes of lake carbonates in arid areas, we examined the carbon isotopic composition of ostracods, bulk carbonate, fine-grained carbonates, and associated water DIC (dissolved inorganic carbon) from Lake Qinghai and several small lakes and ponds surrounding Lake Qinghai. We obtained three major results. 1) The carbon isotopic compositions of ostracods, bulk carbonate, and fine-grained carbonates in the lakes and ponds are clearly correlated with water 未¹³C_DIC values, which vary with water salinity in the Lake Qinghai area. 2) The variation in the 未¹³C_DIC values of lake water is mainly controlled by CO₂ exchanges between the atmosphere and lake waters in the Lake Qinghai area. 3) Ostracods, bulk carbonate and fine-grained carbonates show consistent trends of isotopic composition in the study area, and the differences in carbon isotopic composition between authigenic carbonates and ostracods may be explained by the differences in carbon isotopic composition between the DIC of surface water and that of the water near to the sediment-water interface as well as the 鈥榲ital offsets鈥?of ostracods.

Our results suggest that variations in the 未¹³C values of carbonates in Lake Qinghai and other lakes in this arid, high-altitude area are primarily controlled by the carbon-isotope ratios of the lake water DIC, which in turn are related to water salinity. Therefore, changes in carbonate 未¹³C values may be used to indirectly indicate changes in water salinity in the Lake Qinghai area.