A potential suite of climate markers of long-chain n-alkanes and alkenones preserved in the top sediments from the Pacific sector of the Southern Ocean

• Published in: Progress in earth and planetary science 2021-04, Vol.8 (1), p.1-13, Article 23
• Main Authors: Chen, Xin, Liu, Xiaodong, Lin, Da-Cheng, Wang, Jianjun, Chen, Liqi, Yu, Pai-Sen, Wang, Linmiao, Xiong, Zhifang, Chen, Min-Te
• Format: Article
• Language: English
• Subjects: 6. Interdisciplinary research; Atmospheric Sciences; Biogeosciences; Carbon; Carbon isotopes; Carbon isotopic; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Hydrogeology; Long-range transport; Marine sediments; n-alkane; Oceans; Organic compounds; Pacific Ocean; Phytoplankton; Planetology; Quaternary and Future Earth: Harmonious Coexistence of Climate and Humans; Research Article; Sea surface temperature; Sediments; Southern Ocean; SST U 37 k $$ {U}_{37}^{\mathrm{k}}; Surface temperature; Terrestrial environments
• ISSN: 2197-4284; 2197-4284
• DOI: 10.1186/s40645-021-00416-9

Investigating organic compounds in marine sediments can potentially unlock a wealth of new information in these climate archives. Here, we present pilot study results of organic geochemical features of long-chain n -alkanes and alkenones and individual carbon isotope ratios of long-chain n -alkanes from a newly collected, approximately 8 m long, located in the far reaches of the Pacific sector of the Southern Ocean. We analyzed a suite of organic compounds in the core. The results show abundant long-chain n -alkanes (C 29 – C 35 ) with predominant odd-over-even carbon preference, suggesting an origin of terrestrial higher plant waxes via long-range transport of dust, possibly from Australia and New Zealand. The δ 13 C values of the C 31 n -alkane range from − 29.4 to − 24.8‰, in which the higher δ 13 C values suggest more contributions from C 4 plant waxes. In the analysis, we found that the mid-chain n -alkanes (C 23 – C 25 ) have a small odd-over-even carbon preference, indicating that they were derived from marine non-diatom pelagic phytoplankton and microalgae and terrestrial sources. Furthermore, the C 26 and C 28 with lower δ 13 C values (~ − 34‰) indicate an origin from marine chemoautotrophic bacteria. We found that the abundances of tetra-unsaturated alkenones (C 37:4 ) in this Southern Ocean sediment core ranges from 11 to 37%, perhaps a marker of low sea surface temperature (SST). The results of this study strongly indicate that the δ 13 C values of long-chain n -alkanes and U 37 k index are potentially useful to reconstruct the detailed history of C 3 /C 4 plants and SST change in the higher latitudes of the Southern Ocean.