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

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 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 CPI 27-33-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 CPI 27-33-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.

Paleoclimate Variations Spanning the Past 29–4 Ma Inferred From Lipid Biomarkers and Carbon Isotopes in the Linxia Basin, Northeast Tibetan Plateau

“…The use of fossil molecules, such as n-alkanes, alkanoic acids, alkenones, GDGTs and those derived from specific biological sources, and δ 13 C values of TOC to reconstruct paleoclimate has become an important part of molecular stratigraphy (Xie et al, 2003;Fan et al, 2007;Weijers et al, 2007;Wang et al, 2012;Wu et al, 2018;Tian et al, 2019;Wang et al, 2021a;Wang et al, 2021b). Wang et al (2012) analyzed the n-alkanes and n-alkan-2-ones of the sediments collected from the Linxia Basin, and proposed that these biomarkers was in agreement with the palynofloras showing significant variations in response to the climate changes and uplift of the Tibetan Plateau at ~8 Ma.…”

Moisture variation inferred from tree rings in north central China and its links with the remote oceans

“…In China, most meteorological stations were established in the east after the 1960s 13 , 14 , which prevents us from probing into the climate change on longer time scales. Therefore, many researchers use different natural archives, such as lake sediments 15 , 16 , stalagmites 17 , 18 and tree rings 19 – 21 , to decode paleoclimate change at various timescales, and they have made great progress with these methods. Tree rings, as a widespread natural archive, are extensively used because of their high resolution.…”