| Abnormal positive d13C values of carbonate in Lake Caohai, southwest China, and their possible relation to lower temperature | |
| Zhengjie Zhu; Jing’an Chen; Yan Zeng | |
| 2013 | |
| Source Publication | Quaternary International
 |
| Volume | 286Issue:1Pages:85-93 |
| Abstract | Carbon source inputs, CO2 exchange between atmosphere and lake water, as well as lacustrine productivity are commonly served as the main controls on d13C values of authigenic carbonates in lake sediments. Generally, d13C values of recent carbonates in most lakes are lower than þ5& (all values reported here with respect to the PDB standard), and rather few reach up to þ13&. Extreme positive d13C values up to þ23.10& are reported in authigenic carbonate in Lake Caohai, southwest China, and some d13C values are the most positive values in the previously reported surface water carbonate d13C values in lakes. Simultaneously, there are two intervals of large carbonate 13C enrichment during the past 500 years, namely 1670e1714 AD and 1788e1881 AD. On the basis of combination with the oxygen isotopic composition of carbonate and Drought/Flood index proxies (D/F), carbon source inputs, CO2 exchange between atmosphere and lake water can not cause this extreme carbonate 13C enrichment. In addition, the inconsistent between organic matter content and d13C values of carbonate, lower organic matter d13C values, as well as the weak/negative correlation between d13C values of organic matter and carbonate during these two intervals confirmed that lacustrine productivity is also not the dominant factor that controls abnormal positive carbonate d13C values. Temperature variations in Lake Caohai during the past 500 years were reconstructed from co-analysis of d18O values of carbonate and organic matter cellulose, and periods of abnormal positive d13C values of carbonate correspond well with the lower temperature periods. The 1670e1714 AD and 1788e1881 AD cold periods were synchronous with the coldest intervals of Little Ice Age (LIA), and also consistent with the Maunder and Dalton sunspot minimum, respectively. Considering these geochemical data together, although there is no direct effect between temperature and carbonate d13C values, the lower temperature restrains the degradation of organic matter, and bacteria have the chance to participate the carbon isotopic fractionation of organic matter, thus generating the methane (CH4) gas, which has the extreme lower d13C values up to 60&, resulting in the extreme enrichment 13C in carbonates due to the preferential synthesis of 12CH4. The important inputs of bacteria to sedimentary sequence during the periods of 1670e1714 AD and 1788e1881 AD have been further verified by the carbon isotopic fractionation between carbonate and organic matter. Therefore, this mechanism may be responsible for abnormal positive d13C values in Lake Caohai. Abnormal positive d13C values of carbonate in Lake Caohai may be indirectly ascribed to the lower temperature, and more attention should be paid to the carbon isotopic composition of carbonates in Lake Caohai in future research. Particular factors affecting carbonate carbon isotopic composition should be taken into account in order to avoid misinterpreting palaeoclimatic reconstructions. |
| Keyword | Abnormal Positive Carbonate Lake Caohai Lower Temperature Southwest China |
| Subject Area | 地表环境地球化学过程与环境质量变化 |
| Indexed By | SCI |
| Language | 英语 |
| Document Type | 期刊论文 |
| Identifier | http://ir.gyig.ac.cn/handle/352002/4782 |
| Collection | 环境地球化学国家重点实验室_环境地球化学国家重点实验室_期刊论文 |
| Recommended Citation GB/T 7714 | Zhengjie Zhu,Jing’an Chen,Yan Zeng. Abnormal positive d13C values of carbonate in Lake Caohai, southwest China, and their possible relation to lower temperature[J]. Quaternary International,2013,286(1):85-93. |
| APA | Zhengjie Zhu,Jing’an Chen,&Yan Zeng.(2013).Abnormal positive d13C values of carbonate in Lake Caohai, southwest China, and their possible relation to lower temperature.Quaternary International,286(1),85-93. |
| MLA | Zhengjie Zhu,et al."Abnormal positive d13C values of carbonate in Lake Caohai, southwest China, and their possible relation to lower temperature".Quaternary International 286.1(2013):85-93. |
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