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Ironstone as a proxy of Paleozoic ocean oxygenation

Abstract. 

"Marine ironstone is a Phanerozoic biochemical sedimentary rock that contains abundant primary iron. Although rare, ironstone is conspicuous in the Paleozoic sedimentary record. Its iron source remains contentious, with traditional models invoking a continentally derived source. Increasing sedimentologic evidence suggests that many Paleozoic ironstones formed along favourably oriented continental margins where coastal upwelling delivered ferruginous waters, with the postulated source of iron being deep-ocean hydrothermal fluids. [...]".

 

Source: Science Direct 
Authors: Edward J. Matheson et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117715

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Continental configuration controls ocean oxygenation during the Phanerozoic

Abstract. 

"The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O2]) in the ocean. In turn, [O2] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO2). Here, by contrast, we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O2]. [...]". 

 

Source: Nature
Authors: Alexandre Pohl et al.
DOI: https://doi.org/10.1038/s41586-022-05018-z 

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Low oxygen levels with high redox heterogeneity in the late Ediacaran shallow ocean: Constraints from I/(Ca + Mg) and Ce/Ce* of the Dengying Formation

Abstract. 

"Most previous studies focused on the redox state of the deep water, leading to an incomplete understanding of the spatiotemporal evolution of the redox-stratified ocean during the Ediacaran–Cambrian transition. In order to decode the redox condition of shallow marine environments during the late Ediacaran, this study presents I/(Ca + Mg), carbon and oxygen isotope, major, trace, and rare earth element data of subtidal to peritidal dolomite from the Dengying Formation at Yangba, South China. [...]".

 

Source: Wiley Online Library
Authors: Yi Ding et al.
DOI: https://doi.org/10.1111/gbi.12520

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The Fate of Oxygen in the Ocean and Its Sensitivity to Local Changes in Biological Production

Abstract. 

"We investigate the sensitivity of the oxygen content and true oxygen utilization of key low-oxygen regions Ω to pointwise changes in biological production. To understand how the combined water and biogenic particle transport controls the sensitivity patterns and the fate of oxygen in the ocean, we develop new relationships that link the steady-state oxygen content and deficit of Ω to the downstream and upstream oxygen utilization rate (OUR), respectively. We find that the amount of oxygen from Ω that will be lost per unit volume at point r is linked to OUR(r) through the mean oxygen age accumulated in Ω. [...]".

 

Source: Wiley Online Library 
Authors: Mark Holzer
DOI: https://doi.org/10.1029/2022JC018802

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Mo isotope composition of the 0.85 Ga ocean from coupled carbonate and shale archives: Some implications for pre-Cryogenian oxygenation

Abstract.

"This study addresses marine palaeoredox conditions of the mid-Neoproterozoic by analysing the Mo isotope, trace element, and U-Th-Pb isotope compositions of shallow water microbial carbonate, deep water pelagic carbonate, and shale from the Stone Knife Formation (SKF) in NW Canada. The U-Th-Pb isotope SKF systematics of reef microbialite carbonates, and the moderately expressed negative Ce anomalies are consistent with the presence of dissolved O2 in the surface waters. [...]".

 

Source: Science Direct 
Authors: Edel Mary O'Sullivan et al.
DOI: https://doi.org/10.1016/j.precamres.2022.106760

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Nitrogen isotope evidence for oxygenated upper ocean during the Cryogenian interglacial period

Abstract.

"The Cryogenian interglacial period have witnessed dramatic changes in climate, oceanic environment and biological evolution. The nitrogen isotopic composition, as an important biogeochemical proxy, has the potential to track both the nutrient cycling and redox conditions in the past. However, nitrogen isotopic data during this interglacial time is rather limited. Here, we present integrated data for nitrogen isotopes (δ15N), as well as organic carbon isotopes (δ13Corg), iron (Fe) speciation, pyrite morphology and trace elements from the Cryogenian interglacial Datangpo Formation derived from a drill core from South China to figure out the nitrogen cycling and coeval redox states. [...]". 

 

Source: Science Direct 
Authors: Guangyou Zhu et al.
DOI: https://doi.org/10.1016/j.chemgeo.2022.120929

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Geochemical evidence from the Kioto Carbonate Platform (Tibet) reveals enhanced terrigenous input and deoxygenation during the early Toarcian

Abstract.

"The early Toarcian, as registered in a variety of sedimentary archives, was characterized by an abrupt negative carbon-isotope excursion (CIE) typically superimposed on a long-term positive trend, and was accompanied by significant climatic and environmental changes. However, the changes in continental weathering influx and oceanic deoxygenation in shallow waters and their possible role in causing carbonate-platform crises in low latitudes remains poorly constrained. [...]".

 

Source: Science Direct 
Authors: Zhong Han et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103887

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Enhanced phosphorus recycling during past oceanic anoxia amplified by low rates of apatite authigenesis

Abstract.

"Enhanced recycling of phosphorus as ocean deoxygenation expanded under past greenhouse climates contributed to widespread organic carbon burial and drawdown of atmospheric CO2. Redox-dependent phosphorus recycling was more efficient in such ancient anoxic marine environments, compared to modern anoxic settings, for reasons that remain unclear. Here, we show that low rates of apatite authigenesis in organic-rich sediments can explain the amplified phosphorus recycling in ancient settings as reflected in highly elevated ratios of organic carbon to total phosphorus. [...]".

 

Source: Science Advances 
Authors: Nina M. Papadomanolaki et al.
DOI: 10.1126/sciadv.abn2370

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Competing and accelerating effects of anthropogenic nutrient inputs on climate-driven changes in ocean carbon and oxygen cycles

Abstract. 

"Nutrient inputs from the atmosphere and rivers to the ocean are increased substantially by human activities. However, the effects of increased nutrient inputs are not included in the widely used CMIP5 Earth system models, which introduce bias into model simulations of ocean biogeochemistry. Here, using historical simulations by an Earth system model with perturbed atmospheric and riverine nutrient inputs, we show that the contribution of anthropogenic nutrient inputs to past global changes in ocean biogeochemistry is of similar magnitude to the effect of climate change. [...]". 

 

Source: Science Advances
Authors: Akitomo Yamamoto et al. 
DOI: 10.1126/sciadv.abl9207

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Reactive oxygen species in the world ocean and their impacts on marine ecosystems

Abstract. 

"Reactive oxygen species (ROS) are omnipresent in the ocean, originating from both biological (e.g., unbalanced metabolism or stress) and non-biological processes (e.g. photooxidation of colored dissolved organic matter). ROS can directly affect the growth of marine organisms, and can also influence marine biogeochemistry, thus indirectly impacting the availability of nutrients and food sources. Microbial communities and evolution are shaped by marine ROS, and in turn microorganisms influence steady-state ROS concentrations by acting as the predominant sink for marine ROS. [...]".

 

Source: Science Direct 
Authors: J. Jeffrey Morris et al.
DOI: https://doi.org/10.1016/j.redox.2022.102285

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