Climatic and environmental implications from n-alkanes in glacially eroded lake sediments in Tibetan Plateau: An example from Ximen Co |
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Authors: | Pu Yang Zhang HuCai Wang YongLi Lei GuoLiang Nace Trevor Zhang ShuPing |
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Institution: | 1 School of Remote Sensing,Nanjing University of Information Science & Technology,Nanjing 210044,China;2 State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,China;3 Key Laboratory of Petroleum Resources Research,Institute of Geology and Geophysics,Chinese Academy of Sciences,Lanzhou 730000,China;4 Duke University,Division of Earth and Ocean Sciences,Durham,North Carolina 27708-0227,USA |
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Abstract: | Gas chromatography-mass spectrometry was used to identify a series of n-alkanes in the sediments of a typical glacially eroded lake in the eastern Tibetan Plateau. By comparing the distribution
patterns of n-alkanes in lake sediments, surface soils and cow manure, it was shown that n-C27-n-C33 alkanes in the soil ecosystem of Ximen Co are derived from vascular plant species and that the distribution pattern of n-C27-n-C33 alkanes remains unchanged during the feeding and digestion processes of herbivores. The relative percentage of C27, C29 and C31
n-alkanes decreased from the bottom to the top of the sediment core showing a trend of degradation of higher plants in the
Ximen Co lake region during the formation of the 44 cm core. 210Pb dating, combined with pre-existing AMS 14C dating results showed that the depositional core reflects climatic and environmental variations since about 900 years before
present. The n-alkane indexes (ACL27–33, P
aq, P
wax) are comparable with regional temperature variation, especially recording the Little Ice Age event (LIA). This study highlights
that n-alkanes are valid proxies for paleo-climate and paleo-environment reconstruction, despite the same distribution patterns
in n-alkane molecular fossils derived from a typical glacially eroded lake. |
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Keywords: | Tibetan Plateau glacially eroded lake Ximen Co lake sediment molecular fossil n-alkane climatic and environmental change |
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