Omnipresent authigenic calcite distorts Arctic radiocarbon chronology

• Published in: Communications Earth & Environment
• Main Authors: Jutta Erika Wollenburg, Jens Matthiessen, Christoph Vogt, Gernot Nehrke, Hendrik Grotheer, Dorothee Wilhelms-Dick, Walter Geibert, Gesine Mollenhauer
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Portfolio 2023
• Subjects: Geology; QE1-996.5; Environmental sciences; GE1-350; Arctic Basin; Arctic Ocean; Foraminifera*; Planktonic foraminifera
• Online Access: https://doi.org/10.1038/s43247-023-00802-9; https://doaj.org/article/0e5114b3f2b449e2b1c084e9ad0f57fa

Abstract As calcareous foraminifera precipitate their shells from the surrounding water mass, they are the basis of most marine radiocarbon chronologies and paleo-proxies. Nevertheless, post-mortem alteration of shells, especially addition of authigenic calcite, impact proxy records. In the Arctic Ocean, authigenic calcite overgrowth on foraminifera has been attributed to hydrocarbon release, with a single report on 13C-enriched authigenic calcite, indicating a different carbon source. Here, we use comparative radiocarbon, carbon and oxygen isotope measurements to show that this 13C-enriched authigenic calcite impacts a large proportion of Holocene and the majority of last glacial planktonic foraminifera in the Arctic Basin. This authigenic precipitated calcite is 14C-depleted, so overgrowth results in invariably older 14C-ages. We show that, in comparison with published data, the true chronology of Arctic basin sediments can deviate by more than 10,000 years in critical parts of the last deglaciation and that stable oxygen and carbon isotopes, as likely all calcite-based proxy-records are affected with potential implications for paleoclimate models.