AUTHOR=Wu Yingqin , Wang Tong , Liu Yan , Ma Rong , Chen Zhangxin 

TITLE=Carbon Isotope Composition and Geochemical Features of Sediments From Gongga Mountain, China, and Potential Environmental Implications

JOURNAL=Frontiers in Earth Science

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.865575

DOI=10.3389/feart.2022.865575

ISSN=2296-6463

ABSTRACT=<p>Using gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS), the soluble organic matter was analyzed for the first time in twenty-two sediment samples from the eastern slopes of the Gongga Mountain, China, at high altitudes between 4,600 and 6,700 m. The C<sub>11</sub>-C<sub>33</sub><italic>n</italic>-alkanes and C<sub>9</sub>-C<sub>33</sub><italic>n</italic>-alkan-2-ones were identified in these samples. Both compounds were dominated by odd carbon numbers in the long-chain molecules and contained a maximum of <italic>n</italic>-C<sub>27</sub> or <italic>n</italic>-C<sub>29</sub>, indicating that the sediments were predominantly of higher plant origin. However, the short-chain <italic>n</italic>-alkan-2-ones, with a maximum content of <italic>n</italic>-C<sub>17</sub> or <italic>i</italic>-C<sub>18</sub> (phytone, 6, 10, 14-trimethylpentadecan-2-one), did not show a predominance of odd and even numbers, suggesting that they were predominantly derived from bacteria and algae. Therefore, we suggest that the organic matter in Gongga Mountain comes from three sources, i.e. bacteria, algae, and higher plants. Stable carbon isotope (δ<sup>13</sup>C) values ranged from −24.6‰ to −27.3‰, indicating that C<sub>3</sub> plants were the dominant organic input to the sediments and suggesting a relatively colder and drier depositional environment. However, C<sub>4</sub> plants increase sharply at high altitudes of 6,300–6,600 m, suggesting that the paleoclimate of Gongga Mountain became drier and wetter with the increase of altitude.</p>