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 largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we show that carbonate-associated sulfate (CAS) from three different paleocontinents all have conspicuous negative 17O anomalies (Δ′17OCAS values down to −0.53‰) during the SE. [...]".

Source: Nature
Authors: Haiyang Wang et al.
DOI: https://doi.org/10.1038/s41467-023-39962-9

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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 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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Abstract. 

"The Mo isotope composition of late Ediacaran global seawater and the global extent of ocean oxygenation are still debated due to the complex controls on sedimentary Mo isotope compositions and the rarity with which sediments directly capture global seawater Mo isotope compositions. Deep-water sulfidic sediments from modern severely restricted basins like the Black Sea have the best chance of capturing global seawater Mo isotope compositions. However, few studies have focused on sedimentary Mo isotope variations and their causes in late Ediacaran restricted basins. [...]". 

Source: Science Direct
Authors: Zhaozhao Tan et al.
DOI: https://doi.org/10.1016/j.chemgeo.2023.121410

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Abstract. 

"The ocean is a net source of the greenhouse gas and ozone-depleting substance, nitrous oxide (N2O), to the atmosphere. Most of that N2O is produced as a trace side product during ammonia oxidation, primarily by ammonia-oxidizing archaea (AOA), which numerically dominate the ammonia-oxidizing community in most marine environments. The pathways to N2O production and their kinetics, however, are not completely understood. Here, we use 15N and 18O isotopes to determine the kinetics of N2O production and trace the source of nitrogen (N) and oxygen (O) atoms in N2O produced by a model marine AOA species, Nitrosopumilus maritimus. [...]".

Source: Proceedings of the National Academy of Sciences
Authors: Xianhui S. Wan et al.
DOI: https://doi.org/10.1073/pnas.2220697120

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Abstract.

"Before the Quaternary, the Earth experienced a series of environmental perturbations. The causal links between large volcanic events, extreme climatic change, and ocean anoxia have been examined in the context of these perturbations. However, to date, the correlation between oceanic anoxia and large volcanic activity in the Pleistocene remains poorly constrained. Identifying the physical processes that can control changes to the marine osmium, uranium, and sulfur isotope ratios is critical to understanding how volcanic activity, climate changes, and ocean anoxia have coevolved throughout the Quaternary. [...]".

Source: Science Direct 
Authors: Wenlong Pei et al. 
DOI: https://doi.org/10.1016/j.palaeo.2022.111360

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Abstract.

"A Tremadocian (Early Ordovician, base Stairsian North American Stage) mass extinction event is recorded globally in rocks from several ancient continents and is accompanied by a globally correlated positive carbon isotope excursion (CIE; the largest during the Early Ordovician). In this study, elemental concentrations and uranium isotope compositions (δ238U) were measured for carbonate samples from three sections (along a proximal-to-distal transect: Ibex area, Shingle Pass, Meiklejohn Peak, respectively) in the Great Basin to test the role of ocean anoxia/euxinia on the base Stairsian mass extinction event. [...]".

Source: Science Direct 
Authors: Xinze Lu et al. 
DOI: https://doi.org/10.1016/j.gca.2022.11.028

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Abstract. 

"Early animals experienced multiple-phase radiations and extinctions from the late Ediacaran to early Cambrian. Oxygen likely played an important role in these evolutionary events, but detailed marine redox evolution during this period remains highly debated. The emerging vanadium (V) isotope system can better capture short-term perturbations to global ocean redox conditions. In this study, we analyzed V isotope compositions [...]".

Source: Science Direct 
Authors: Wei Wei et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117942

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Abstract. 

"Ocean acidification causes biocalcification stress. The calcium isotope composition of carbonate producers can archive such stress because calcium isotope fractionation is sensitive to precipitation rate. Here, we synthesize morphometric observations of planktic foraminifera with multi-archive calcium isotope records from Gubbio, Italy and the Western Interior Seaway spanning Cretaceous Ocean Anoxic Event 2 (~94 million years ago). Calcium isotope ratios increase ~60 thousand years prior to the event. [...]". 

Source: Nature
Authors: Gabriella D. Kitch et al.
DOI: https://doi.org/10.1038/s43247-022-00641-0

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