Ossa Ossa, F, Hofmann, A, Spangenberg, JE et al. (7 more authors) (2019) Limited oxygen production in the Mesoarchean ocean. Proceedings of the National Academy of Sciences, 116 (14). pp. 6647-6652. ISSN 0027-8424
Abstract
The Archean Eon was a time of predominantly anoxic Earth surface conditions, where anaerobic processes controlled bioessential element cycles. In contrast to “oxygen oases” well documented for the Neoarchean [2.8 to 2.5 billion years ago (Ga)], the magnitude, spatial extent, and underlying causes of possible Mesoarchean (3.2 to 2.8 Ga) surface-ocean oxygenation remain controversial. Here, we report δ15N and δ13C values coupled with local seawater redox data for Mesoarchean shales of the Mozaan Group (Pongola Supergroup, South Africa) that were deposited during an episode of enhanced Mn (oxyhydr)oxide precipitation between ∼2.95 and 2.85 Ga. Iron and Mn redox systematics are consistent with an oxygen oasis in the Mesoarchean anoxic ocean, but δ15N data indicate a Mo-based diazotrophic biosphere with no compelling evidence for a significant aerobic nitrogen cycle. We propose that in contrast to the Neoarchean, dissolved O2 levels were either too low or too limited in extent to develop a large and stable nitrate reservoir in the Mesoarchean ocean. Since biological N2 fixation was evidently active in this environment, the growth and proliferation of O2-producing organisms were likely suppressed by nutrients other than nitrogen (e.g., phosphorus), which would have limited the expansion of oxygenated conditions during the Mesoarchean.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2019 Published under the PNAS license. This is an author produced version of a paper published in PNAS. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | oxygen oasis; nitrogen isotopes; nutrient limitation; oxygenic photosynthesis; Mesoarchean |
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) > Earth Surface Science Institute (ESSI) (Leeds) |
Funding Information: | Funder Grant number Royal Society WM150108 Leverhulme Trust Not Known |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Mar 2019 10:20 |
Last Modified: | 24 May 2019 07:55 |
Status: | Published |
Publisher: | National Academy of Sciences |
Identification Number: | 10.1073/pnas.1818762116 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:143148 |