Tao, J, Zhang, J, Liu, Y et al. (6 more authors) (2022) A stable and moderate nitrate pool in largely anoxic Mesoproterozoic oceans and implications for eukaryote evolution. Precambrian Research, 381. 106868. ISSN 0301-9268
Abstract
The Mesoproterozoic (1.6–1.0 Ga) is a particularly important interval in Earth history that witnessed the initial radiation of eukaryotic life. Ocean anoxia and nutrient limitation has been invoked to explain the delayed expansion of more complex, multicellular eukaryotes during the Mesoproterozoic. However, pulsed oxygenation events and elevated nitrate availability have been identified in shallow marine settings. In deeper waters, however, nitrate availability and potential links to eukaryotic evolution remain poorly constrained. Here, we report an integrated geochemical study based on multiple proxies conducted on two new drill-core sections from the ∼1460 Ma Hongshuizhuang Formation and the ∼1380 Ma Xiamaling Formation, North China. Iron speciation and redox-sensitive trace element systematics suggest dominantly ferruginous to weakly euxinic water column conditions during deposition of both units. Our data are consistent with previous inferences of persistently anoxic deep water conditions in Mesoproterozoic oceans. Exclusively positive δ15N (+3.1 ± 0.8 ‰) values reveal the operation of partial denitrification in the water column, implying a relatively stable and moderate nitrate pool in offshore surface waters. Furthermore, a compilation of the Mesoproterozoic sedimentary δ15N record suggests a global nearshore to offshore oceanic nitrate gradient, with minimal but still bioavailable nitrate in offshore environments. The overall size of the nitrate pool was therefore apparently smaller than that of eukaryote-dominated modern oceans. Coupling Mesoproterozoic sedimentary δ15N data with fossil and biomarker records, we propose that this moderate level of nitrate may have been able to sustain a relatively low abundance of eukaryotic primary producers in the marine ecosystem, but was still not sufficient to trigger eukaryotic diversification and the rise of eukaryotes to ecological dominance.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2022 Elsevier B.V. All rights reserved. This is an author produced version of an article published in Precambrian Research. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Eukaryote evolution; Mesoproterozoic; Nitrate pool; North China; Ocean redox |
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) |
Depositing User: | Symplectic Publications |
Date Deposited: | 27 Sep 2022 14:07 |
Last Modified: | 07 Oct 2023 00:13 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.precamres.2022.106868 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:191243 |