Luo, J, Long, X, Bowyer, FT et al. (6 more authors) (2021) Pulsed oxygenation events drove progressive oxygenation of the early Mesoproterozoic ocean. Earth and Planetary Science Letters, 559. 116754. ISSN 0012-821X
Abstract
The Mesoproterozoic era has long been considered a time of relative environmental and biological stasis. However, emerging insight suggests that this period may have been more dynamic than previously considered, both in terms of oxygenation and potential consequences for biological evolution. Nevertheless, our understanding of this immense period of time remains limited. To provide more detailed constraints on oxygenation dynamics, we report a multiproxy geochemical study of an early Mesoproterozoic (∼1600–1540 million years ago, Ma) carbonate-dominated succession from the North China craton. We include inorganic carbon isotope (), iron-speciation, and major and trace element data, in addition to molybdenum isotopic compositions (). These geochemical data support previous inferences of persistent anoxic and ferruginous deeper water conditions in the earliest Mesoproterozoic ocean, with limited oxygenation of surface waters. However, the behaviour of these redox-sensitive geochemical proxies reveals pulsed oxygenation events, with each event increasing the maximum depth of oxygenation, leading to overall progressive oxygenation of the ocean. During these pulsed oxygenation events we find the lightest Mo isotope signatures ever measured in the rock record, which we attribute to initial drawdown of isotopically light Mo in association with extensive Mn and Fe (oxyhydr)oxide precipitation, followed by diagenetic recycling. However, shallower water sediments deposited after the pulses of deeper water oxygenation more faithfully record the Mo isotopic composition of coeval seawater. For these samples, we utilise a single reservoir Mo cycling model, constrained by an updated estimate of Mesoproterozoic seawater Mo concentration, and scaled using a function associated with differential organic carbon flux between the shelf and basin. When scaled to modern rates of Mo accumulation under variable marine redox conditions, our modelling estimates suggest a minimum oxic seafloor area of ∼30% of the total seafloor area at ∼1540 Ma. It remains unclear whether the oxygenation observed across this ∼60 million year interval represents a progressive transition to a more persistently oxygenated ocean, or whether oceanic oxygen levels fluctuated considerably through the later Mesoproterozoic.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 Elsevier B.V. All rights reserved. This is an author produced version of an article published in Earth and Planetary Science Letters. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Mesoproterozoic; palaeoredox; Fe speciation; molybdenum isotopes; ocean oxygenation |
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 NERC (Natural Environment Research Council) NE/R010129/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 12 Jan 2021 14:30 |
Last Modified: | 26 Jan 2022 01:38 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.epsl.2021.116754 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:169797 |
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