Dynamic ocean redox conditions during the end-Triassic mass extinction: Evidence from pyrite framboids

A peculiar record of previously undescribed and/ or rarely described nannoliths from the Hettangian to lower Pliensbachian of the Llanbdr (Mochras Farm) core, Wales (UK) is documented here. Some of the observed morphotypes are assigned to didemnid ascidians, commonly observed in the upper Rhaetian, as evidence of the resilience of ascidian tunicates during the end-Triassic mass extinction. One newly described nannolith present throughout the Hettangian and Sinemurian, Quadrifolium hesselboi, is similar to forms previously observed in the upper Rhaetian, and is therefore considered to be a new nannofossil survivor from the end-Triassic mass extinction. High-amplitude changes observed in the absolute and relative abundances of nannoliths, schizosphaerellids and coccoliths across the Hettangian suggest a recovery interval from the end-Triassic crisis spanning the planorbis-liasicus ammonite zones in four distinct steps with high volatility in environmental conditions, followed by the establishment of more stable environmental conditions in the angulata ammonite zone.

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“…2020 and Li et al . 2022), in some cases even spreading to the photic zone in shallow epicontinental seas (Richoz et al . 2012; Fox et al .…”

Section: Discussionmentioning

confidence: 99%

On the occurrence of rare nannoliths (calcareous nannofossils) in the Early Jurassic and their implications for the end‐Triassic mass extinction

Paulsen

Thibault

2023

Papers in Palaeontology

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“…This method was initially tested using Jurassic sediments by Wignall & Newton (1998), and subsequently, pyrite framboids have often been employed in order to decipher redox conditions prevailing in many palaeoenvironments of different ages (e.g. Zhou & Jiang, 2009; Hammarlund et al 2012; Huang et al 2017; Li et al 2022).…”

Section: Methodsmentioning

confidence: 99%

Weak and intermittent anoxia during the mid-Tournaisian (Mississippian) anoxic event in the Montagne Noire, France

Rakociński

Książak²,

Pisarzowska³

et al. 2023

Geol. Mag.

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The mid-Tournaisian black radiolarian cherts of the Lydiennes Formation are exposed in deep-shelf successions of the Puech de la Suque and Col des Tribes sections of the Mont Peyroux Nappe area in the Montagne Noire, southern France. This interval represents the mid-Tournaisian anoxic event that is also termed the Lower Alum Shale Event. This event is associated with a global marine transgression that was characterized by increased productivity and drastic facies changes from pelagic carbonate sedimentation to the widespread deposition of black organic-rich siliceous shales and radiolarites in many parts of the world. In the present study, high-resolution inorganic geochemistry and framboidal pyrite analyses were employed to decipher changes in depositional conditions during the mid-Tournaisian anoxic event in the Montagne Noire. The results show that the total organic carbon contents of sediments associated with the Lower Alum Shale Event vary from 0.09 to 1.9 wt %. These low to moderate total organic carbon contents, high U/Th, low Corg/P and intermediate V/Cr ratios, enrichment in redox-sensitive trace elements, such as U, Mo and V, as well as varying sizes of pyrite framboids, indicate periodic dysoxic to anoxic bottom-water conditions during deposition of the studied sediments. Anomalous Hg spikes (>500 ppb) are also reported in the mid-Tournaisian deep-water marine succession of the Montagne Noire in the present study, which confirm a possible influence of increased regional volcanic activity during this environmental turnover.

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Chemofacies characterization of lacustrine shale based on machine learning classification: A case study from the Dongying depression, Bohai bay basin, China

Li,

Lin,

et al. 2024

Geoenergy Science and Engineering

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Dynamic ocean redox conditions during the end-Triassic mass extinction: Evidence from pyrite framboids

Cited by 3 publications

References 83 publications

On the occurrence of rare nannoliths (calcareous nannofossils) in the Early Jurassic and their implications for the end‐Triassic mass extinction

On the occurrence of rare nannoliths (calcareous nannofossils) in the Early Jurassic and their implications for the end‐Triassic mass extinction

Weak and intermittent anoxia during the mid-Tournaisian (Mississippian) anoxic event in the Montagne Noire, France

Chemofacies characterization of lacustrine shale based on machine learning classification: A case study from the Dongying depression, Bohai bay basin, China

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