Xu, L., Shi, X., Poulton, S. orcid.org/0000-0001-7621-189X et al. (7 more authors) (Accepted: 2025) Shallow seawater oxygenation at ca. 1.44 Ga: A reflection of local seafloor oxygen oases or extensive water-column oxygenation? Geological Society of America Bulletin. ISSN 0016-7606 (In Press)
Abstract
It has been suggested that local marine oxygen oases could have formed during the Archean through the oxygenic photosynthesis of microbial mats residing in stromatolites. The ensuing mid-Proterozoic (~1.8–0.8 Ga) was characterized by overall low atmospheric oxygen levels and pervasive oceanic anoxia below a shallow chemocline, but with increasing evidence for several intervals of transient oxygenation. However, since some of the oxygenation intervals have largely been documented by stromatolites, it remains unclear whether these oxygenation signals represent local seafloor oxygen oases or extensive seawater oxygenation. To address this issue, we have conducted a comparative investigation of the mineralogy and geochemistry of stromatolite-rich and stromatolite-poor sections formed during a prominent oxygenation interval in the ~1.44 Ga Tieling Formation of North China. Similar iodine concentration and cerium anomaly characteristics in the stromatolite column and inter-column carbonates suggest that no significant difference existed in terms of redox conditions between the stromatolites and the surrounding water column. Furthermore, the stromatolite-rich interval exhibits lower I/(Ca+Mg) values relative to the contemporaneous stromatolite-poor interval. This indicates that the photosynthetic oxygen production capacity of microbial mats developed in the Tieling Formation was limited, and insufficient to elevate seafloor oxygen levels significantly. After considering our high-resolution I/(Ca+Mg) and carbonate-carbon isotope data alongside seawater redox investigations of other contemporary basins, we argue that the ~1.44 Ga interval of oxygenation may represent an extensive shallow seawater oxygenation event across multiple basins, but with local redox heterogeneity. Our study therefore provides new insight into the nature of oxygenation events recorded by stromatolites during the mid-Proterozoic.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This is an author produced version of an article accepted for publication in GSA Bulletin, made available under the terms of the Creative Commons Attribution License (CC-BY), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. |
Keywords: | stromatolites; microbial mats; photosynthetic oxygen production capacity; redox conditions; Tieling Formation; North China |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 27 Mar 2025 11:56 |
Last Modified: | 27 Mar 2025 16:14 |
Status: | In Press |
Publisher: | Geological Society of America |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:224894 |