Distribution of n-alkan-2-ones in Qionghai Lake sediments,southwest China,and its potential for late Quaternary paleoclimate reconstruction |
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| Authors: | Gen Wang Yongli Wang Zhifu Wei Wei He Ting Zhang Xueyun Ma Xiaoli Yu |
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| Institution: | 1. Key Laboratory of Petroleum Resources Research, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China;2. Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences;3. CAS Center for Excellence in Life and Paleoenvironment, Beijing, China;4. Key Laboratory of Petroleum Resources Research, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China
University of Chinese Academy of Sciences, Beijing, China |
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| Abstract: | Studies on long-chain n-alkan-2-ones from lake sediments remain sparse. In this study, we present an n-alkan-2-one record from Qionghai Lake, southwest China, to assess the paleoclimate significance of variations in their compositions. A homologous series of n-alkan-2-ones ranging from C21 to C35 were identified, with maximum concentrations of the C29 or C31 chain lengths and a strong odd-over-even predominance. This type of n-alkan-2-one is considered to derive mainly from microbial oxidation of the corresponding n-alkanes, and partial inputs from plants. The n-alkan-2-one-derived average chain length (ACL) and carbon preference index (CPI) values changed significantly over the past 28k cal a bp , consistent with the sediment grain size and n-alkane proxies from the same core. Generally, the high CPI27-33-ket and low ACL27-33-ket values indicated cold and dry climates such as for the Last Glacial Maximum (23.2–19.7k cal a bp ), Heinrich 1 event (17.6–15.6k cal a bp ) and Younger Dryas (12.8–11.6k cal a bp ), but low CPI27-33-ket and high ACL27-33-ket values denoted a warm and humid Holocene Climatic Optimum (7.0–4.3k cal a bp ). Therefore, n-alkan-2-ones have great paleoclimatic potential and can be applied together with other biomarkers to reconstruct a reliable paleoclimate record in lake sediments. |
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| Keywords: | biomarkers lake sediments late Pleistocene paleoclimatic changes southwest monsoon |
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