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Extensive marine anoxia in the European epicontinental sea during the end-Triassic mass extinction

Abstract. 

"Warming-induced marine anoxia has been hypothesized as an environmental stressor for the end-Triassic mass extinction (ETME), but links between the spread of marine anoxia and the two phases of extinction are poorly constrained. Here, we report iron speciation and trace metal data from the Bristol Channel Basin and Larne Basin of the NW European epicontinental sea (EES), spanning the Triassic–Jurassic (T–J) transition (~ 202–200 Ma). Results show frequent development of anoxic-ferruginous conditions, interspersed with ephemeral euxinic episodes in the Bristol Channel Basin during the latest Rhaetian, whereas the contemporaneous Larne Basin remained largely oxygenated, suggesting heterogeneous redox conditions between basins. Subsequently, more persistent euxinic conditions prevailed across the T–J boundary in both basins, coinciding precisely with the second phase of the ETME. [...]". 

 

Source: Science Direct

Authors: Tianchen He et al. 

DOI: https://doi.org/10.1016/j.gloplacha.2022.103771

Read the full article here.


Shallow ocean oxygen decline during the end-Triassic mass extinction

Abstract.

"The end-Triassic mass extinction (ETME) was associated with intensified deep-water anoxia in epicontinental seas and mid-depth waters, yet the absolute oxygenation state in the shallow ocean is uncharacterized. Here we report carbonate-associated iodine data from the peritidal Mount Sparagio section (Southern Italy) that documents the ETME (~ 200 Ma) in the western Tethys. We find a sharp drop in carbonate I/(Ca + Mg) ratios across the extinction horizon and persisting into the Early Jurassic. [...]".

 

Source: Science Direct

Authors: Tianchen He et al.

DOI: https://doi.org/10.1016/j.gloplacha.2022.103770

Read the full article here. 


Multiple episodes of extensive marine anoxia linked to global warming and continental weathering following the latest Permian mass extinction

Abstract.

"Explaining the ~5-million-year delay in marine biotic recovery following the latest Permian mass extinction, the largest biotic crisis of the Phanerozoic, is a fundamental challenge for both geological and biological sciences. Ocean redox perturbations may have played a critical role in this delayed recovery. However, the lack of quantitative constraints on the details of Early Triassic oceanic anoxia (for example, time, duration, and extent) leaves the links between oceanic conditions and the delayed biotic recovery ambiguous. [...]"

Source: Science Advances
Authors: Feifei Zhan et al.
DOI:10.1126/sciadv.1602921

Read the full article here.


Uranium isotope evidence for an expansion of marine anoxia during the end-Triassic extinction

Abstract.

"The end-Triassic extinction coincided with an increase in marine black shale deposition and biomarkers for photic zone euxinia, suggesting that anoxia played a role in suppressing marine biodiversity. However, global changes in ocean anoxia are difficult to quantify using proxies for local anoxia. Uranium isotopes (δ238U) in CaCO3 sediments deposited under locally well-oxygenated bottom waters can passively track seawater δ238U, which is sensitive to the global areal extent of seafloor anoxia due to preferential reduction of 238U(VI) relative to 235U(VI) in anoxic marine sediments. [...]"

Source: Geochemistry, Geophysics, Geosystems
Authors: Adam B. Jost et al.
DOI: 10.1002/2017GC006941

Read the full article here.


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