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
• Main Authors: Xin Chen, Xiaodong Liu, Da-Cheng Lin, Jianjun Wang, Liqi Chen, Pai-Sen Yu, Linmiao Wang, Zhifang Xiong, Min-Te Chen
• Format: Article in Journal/Newspaper
• Language: English
• Published: SpringerOpen 2021
• Subjects: Southern Ocean; Pacific Ocean; n-alkane; Carbon isotopic; SST U 37 k $$ {U}_{37}^{\mathrm{k}} $$; Geography. Anthropology. Recreation; G; Geology; QE1-996.5; New Zealand; Pacific
• Online Access: https://doi.org/10.1186/s40645-021-00416-9; https://doaj.org/article/d7cff53cb1084193907bbb204f8ee9a0

Abstract 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 (C29 –C35) 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 δ13C values of the C31 n-alkane range from −29.4 to −24.8‰, in which the higher δ13C values suggest more contributions from C4 plant waxes. In the analysis, we found that the mid-chain n-alkanes (C23 –C25) 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 C26 and C28 with lower δ13C values (~−34‰) indicate an origin from marine chemoautotrophic bacteria. We found that the abundances of tetra-unsaturated alkenones (C37:4) 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 δ13C values of long-chain n-alkanes and U 37 k $$ {U}_{37}^{\mathrm{k}} $$ index are potentially useful to reconstruct the detailed history of C3/C4 plants and SST change in the higher latitudes of the Southern Ocean.