The benthic foraminiferal δ34S records flux and timing of paleo methane emissions

• Published in: Scientific Reports
• Main Authors: Borrelli, C., Gabitov, R. I., Liu, M.-C., Hertwig, A. T., Panieri, G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2020
• Subjects: Multidisciplinary; Arctic; Arctic Ocean; Foraminifera*
• Online Access: http://dx.doi.org/10.1038/s41598-020-58353-4; http://www.nature.com/articles/s41598-020-58353-4.pdf; http://www.nature.com/articles/s41598-020-58353-4

Abstract In modern environments, pore water geochemistry and modelling simulations allow the study of methane (CH 4 ) sources and sinks at any geographic location. However, reconstructing CH 4 dynamics in geological records is challenging. Here, we show that the benthic foraminiferal δ 34 S can be used to reconstruct the flux (i.e., diffusive vs. advective) and timing of CH 4 emissions in fossil records. We measured the δ 34 S of Cassidulina neoteretis specimens from selected samples collected at Vestnesa Ridge, a methane cold seep site in the Arctic Ocean. Our results show lower benthic foraminiferal δ 34 S values (∼20‰) in the sample characterized by seawater conditions, whereas higher values (∼25–27‰) were measured in deeper samples as a consequence of the presence of past sulphate-methane transition zones. The correlation between δ 34 S and the bulk benthic foraminiferal δ 13 C supports this interpretation, whereas the foraminiferal δ 18 O-δ 34 S correlation indicates CH 4 advection at the studied site during the Early Holocene and the Younger-Dryas – post-Bølling. This study highlights the potential of the benthic foraminiferal δ 34 S as a novel tool to reconstruct the flux of CH 4 emissions in geological records and to indirectly date fossil seeps.