Predominance of even carbon-numbered n-alkanes from lacustrine sediments in Linxia Basin,NE Tibetan Plateau: Implications for climate change |
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| Authors: | Yongli Wang Xiaomin Fang Tongwei Zhang Yuanmao Li Yingqin Wu Daxiang He Youxiao Wang |
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| Institution: | 1. Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, China;2. Institute of Tibetan and Plateau Research, Chinese Academy of Sciences, Beijing 100085, China;3. Key Laboratory of Western Resources and Environment of Education Ministry, College at Earth and Environment Sciences, University of Lanzhou, Lanzhou 730000, China |
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| Abstract: | This study reports the first observation of predominant even C-numbered n-alkanes from sediments in the continuous lacustrine-sedimentary section (Maogou) from the Late Miocene to the Early Pliocene (13–4.4 Ma) in the Linxia Basin, NE Tibetan Plateau. The n-alkanes showed a bimodal distribution that is characterised by a centre at n-C16–n-C20 with maximum values at n-C18 and n-C27–n-C31 as well as at n-C29. The first mode shows a strong even C-number predominance (OEP16–20 0.34–0.66). In contrast, the second mode has a strong odd C-number predominance (OEP27–31 1.20–2.45). Certain types of special autochthonous bacteria are a possible source for this distribution of even C-numbered n-alkanes in lacustrine sediments. These bacteria may have a high production rate in weak oxic–anoxic and arid depositional environments, in which a variety of geochemical parameters have recorded palaeoclimate change. |
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