Distribution of n-alkan-2-ones in Qionghai Lake sediments, southwest China, and its potential for late Quaternary paleoclimate reconstruction

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 C-21 to C-35 were identified, with maximum concentrations of the C-29 or C-31 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 ACL(27-33)-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 ACL(27-33)-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. Copyright (c) 2021 John Wiley & Sons, Ltd.