Reconciling biogeochemical redox proxies

• Verfasst von: Li, Siqi [VerfasserIn]
• Verfasst von: Friedrich, Oliver [VerfasserIn]
• Verfasst von: Nielsen, Sune G. [VerfasserIn]
• Verfasst von: Wu, Fei [VerfasserIn]
• Verfasst von: Owens, Jeremy D. [VerfasserIn]
• Titel: Reconciling biogeochemical redox proxies
• Titelzusatz: tracking variable bottom water oxygenation during OAE-2 using vanadium isotopes
• Verf.angabe: Siqi Li, Oliver Friedrich, Sune G. Nielsen, Fei Wu, Jeremy D. Owens
• E-Jahr: 2023
• Jahr: 1 September 2023
• Umfang: 11 S.
• Illustrationen: Illustrationen
• Fussnoten: Online verfügbar: 12. Juni 2023 ; Gesehen am 22.08.2023
• Titel Quelle: Enthalten in: Earth and planetary science letters
• Ort Quelle: Amsterdam [u.a.] : Elsevier, 1966
• Jahr Quelle: 2023
• Band/Heft Quelle: 617(2023) vom: Sept., Artikel-ID 118237, Seite 1-11
• ISSN Quelle: 1385-013X
• DOI: doi:10.1016/j.epsl.2023.118237
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: bottom water redox fluctuations
• Sach-SW: oceanic anoxic event-2
• Sach-SW: sedimentary V isotope compositions
• Sach-SW: short-term bottom water oxygenation
• K10plus-PPN: 1857212223

Abstract

Oceanic Anoxic Event-2 (OAE-2, ∼94 Ma ago) is marked by a significant perturbation to the carbon and nutrient cycles. Despite the general idea of widespread expansion of the oceanic anoxia during OAE-2, various localities likely experienced heterogeneous redox fluctuations throughout the roughly 500-thousand-year-long event. In certain localities, redox-sensitive elements imply persistent anoxic-to-euxinic conditions, notwithstanding paleontological data that indicate short-term hypoxic-to-anoxic oscillations in bottom waters. Such discrepancies likely result from sampling resolution, local proxy sensitivity, and/or time-integration of signals, particularly for severe hypoxic conditions. We applied vanadium (V) isotopes to three well-studied OAE-2 localities in the proto-North Atlantic Basin. Under the relatively stable anoxic-to-euxinic conditions throughout OAE-2 at Well S75 and Site 367, the sedimentary δ51V values present consistent variations analogous to modern anoxic-to-euxinic environments. However, at Site 1258, the sedimentary δ51V values present greater perturbations toward more negative values that are indicative of short-term oxygenation in bottom waters. These negative perturbations of δ51V values covary with the abundances of the low-oxygen-tolerant benthic foraminifers. Together, these data refine the heterogeneous redox fluctuations in individual localities, revealing occasional short-term weak oxygenation under the generally anoxic conditions throughout OAE-2. This study documents the unique utility of V isotopes to track bottom water redox fluctuations, particularly short-term variations from anoxic to mildly oxic conditions that are hard to track with other methods.