Reconciling biogeochemical redox proxies: tracking variable bottom water oxygenation during OAE-2 using vanadium isotopes
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...
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| Main Authors: | , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
1 September 2023
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| In: |
Earth and planetary science letters
Year: 2023, Volume: 617, Pages: 1-11 |
| ISSN: | 1385-013X |
| DOI: | 10.1016/j.epsl.2023.118237 |
| Online Access: | lizenzpflichtig lizenzpflichtig 
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| Author Notes: | Siqi Li, Oliver Friedrich, Sune G. Nielsen, Fei Wu, Jeremy D. Owens |
| Summary: | 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. |
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| Item Description: | Online verfügbar: 12. Juni 2023 Gesehen am 22.08.2023 |
| Physical Description: | Online Resource |
| ISSN: | 1385-013X |
| DOI: | 10.1016/j.epsl.2023.118237 |