Abstract.

"Late Devonian (ca. 360 Ma), Early Carboniferous (ca. 330 Ma), and Early Triassic (ca. 250 Ma) manganese deposits in the South China Block support an emerging view that some Mn carbonates form through direct synsedimentary (authigenic) precipitation. These Mn carbonates accumulated on distal shelves and are interbedded with lime mudstone and heterozoan carbonates that accumulated in coastal upwelling environments. Lithofacies, Ce anomalies combined with vanadium, uranium, and molybdenum enrichments indicate that the Mn carbonates were primarily precipitated under anoxic conditions. [...]".

Source: Science Direct 
Authors: Fangge Chen et al.
DOI: https://doi.org/10.1016/j.epsl.2023.118385

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Abstract.

"This study provides a detailed examination of a condensed Cenomanian-Turonian (C-T) succession of two sections (Dokan Dam and Khalakan) in the Kurdistan Region, Northeastern Iraq, based on biostratigraphy (calcareous nannofossils and planktic foraminifera), carbon and oxygen isotope geochemistry, and facies analysis. The C/T boundary in this region is characterized by a hiatus noticeable due to the absence of the Globigerinelloides benthonensis and Dicarinella hagni subzones and the lack of positive carbon isotope excursion (CIE) peak b during the Oceanic Anoxic Event 2 (OAE2). [...]".

Source: Science Direct
Authors: Fadhil A. Lawa et al.
DOI: https://doi.org/10.1016/j.jafrearsci.2023.105064

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Abstract.

"Oceanic anoxic events (OAEs) represent discrete intervals of decreased marine oxygen concentrations often associated with volcanism, enhanced organic carbon burial coupled with positive δ13C excursions, and significant biotic turnover. Cretaceous OAE 2 (ca. 94 Mya) is especially notable for globally-distributed changes in calcareous invertebrate and plankton populations. While the presence of organic-rich facies is consistent with locally anoxic environments in many cases, determining the global extent of anoxia is more problematic. [...]".

Source: Science Direct
Authors: Joseph T. Kulenguski et al.
DOI: https://doi.org/10.1016/j.palaeo.2023.111756

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Abstract.

"The expansion of oxygen deficient zones (ODZs) within the ocean's interior is anticipated to be a major consequence of anthropogenic climate change, but past changes in ODZs are poorly defined. Recent mapping efforts have revealed plumes of the redox-active metal cobalt within ODZs, driving a basin-scale correlation between high cobalt and low O₂. Here, we investigate the cobalt flux to Equatorial Pacific sediments along the Line Islands Ridge as a novel record of basin-scale fluctuations in ODZ extent. [...]".

Source: Wiley Online Library
Authors: Nicholas J. Hawco & Rhea K. Foreman
DOI: https://doi.org/10.1029/2023GL105135

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Abstract.

"Marine anoxia during the Late Triassic has mostly been reported from the western Tethysand Panthalassa, which were near the Central Atlantic Magmatic Province (CAMP), but whether it developed in global open oceans (e.g., the eastern Tethys) is unknown. Whether the marine anoxia was global or regional requires more research. Here, we present carbonate-associated sulfate (CAS) and pyrite δ34Spy data for the Late Triassic–Early Jurassic interval from the Wenquan Section in Qiantang Basin, Tibet. [...]".

Source: Science Direct
Authors: Wei Tang et al.
DOI: https://doi.org/10.1016/j.jseaes.2023.105659

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Abstract.

"The high enrichment of redox-sensitive elements (RSEs), Mo, U, V, and Cr, in Ediacaran shales was attributed to the Neoproterozoic Oxygenation Event (NOE). However, recent studies have shown that contemporaneous shales from NW Canada do not exhibit RSE enrichment, whereas those from South China exhibit varying degrees of RSE enrichment. Here we investigate RSE records in a broader spatial and temporal distribution of shales within the Ediacaran Doushantuo Formation from South China. [...]".

Source: Science Direct
Authors: Yufei Hao et al.
DOI: https://doi.org/10.1016/j.jseaes.2023.105670

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Abstract.

"Widespread oceanic anoxia marked by globally extensive deposition of organic-rich black shale during the Late Devonian was a major factor in the mass extinctions at the Frasnian-Famennian (FFB, ∼372 million years ago) and Devonian-Carboniferous boundaries (DCB, ∼359 million years ago), although the triggers for these deoxygenation events are still under debate. Here, we apply a novel paleoredox proxy, Hg isotopes, to investigate Late Devonian ocean redox variation and its causes. [...]".

Source: Science Direct
Authors: Wang Zheng et al.
DOI: https://doi.org/10.1016/j.epsl.2023.118175

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Abstract. 

"The availability of oxygen and nutrients during the Mesoproterozoic (1.6–1.0 Ga) is thought to influence the rate of eukaryote evolution. The cause of the transition from low productivity in the upper Wumishan Formation to organic-rich sediments in the Hongshuizhuang Formation remains unknown. We report FeHR/FeT, Fepy/FeHR, MoEF, UEF, VEF, and [Ce/Ce*]SN in one core of the Yanliao Basin to study the redox evolution and compare it with other sections in different depths of the Yanliao Basin to get clues of the spatial and temporal redox heterogeneity. [...]".

Source: Wiley Online Library
Authors: Mingze Ye et al.
DOI: https://doi.org/10.1029/2023GL103598

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Abstract.

"The formation of green rust (GR; a mixed ferric/ferrous hydroxide) and vivianite (ferrous phosphate) are likely to have exerted a major control on phosphorus (P) cycling in ancient anoxic oceans. However, the factors that influence the formation of these minerals under different chemical conditions are poorly constrained, which limits understanding of the pathways that ultimately result in P drawdown and retention in anoxic sediments. This, in turn, limits understanding of P cycling in anoxic oceans and hence potential productivity feedbacks. [...]".

Source: Science Direct
Authors: Yijun Xiong et al.
DOI: https://doi.org/10.1016/j.gca.2023.04.032

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Abstract. 

"The timing and causation of the Capitanian (late Middle Permian) biocrisis remain controversial. Here, a detailed uranium-isotopic (δ238U) profile was generated for the mid-Capitanian to lower Wuchiapingian of the Penglaitan section (the Guadalupian/Lopingian Permian global stratotype) in South China for the purpose of investigating relationships between the biocrisis and coeval oceanic anoxic events (OAEs). Negative δ238U excursions indicate two distinct OAEs, a mid-Capitanian (OAE-C1) and an end-Capitanian (OAE-C2) event. [...]".

Source: Science Direct
Authors: Huyue Song et al.
DOI: https://doi.org/10.1016/j.epsl.2023.118128

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