Phosphorus-cycle disturbances during the Late Devonian anoxic events

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Etat: Public
Version: Final published version
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ID Serval
serval:BIB_D717880D6FC2
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Phosphorus-cycle disturbances during the Late Devonian anoxic events
Périodique
Global and Planetary Change
Auteur⸱e⸱s
Percival L.M.E., Bond D.P.G., Rakociński M., Marynowski L., Hood A.v.S., Adatte T., Spangenberg J.E., Föllmi K.B.
ISSN
0921-8181
Statut éditorial
Publié
Date de publication
01/2020
Peer-reviewed
Oui
Volume
184
Pages
103070
Langue
anglais
Résumé
The Late Devonian was marked by repeated faunal crises and episodes of geographically widespread marine anoxia, and featured one of the ‘Big Five’ mass extinctions of the Phanerozoic Aeon during the Frasnian–Famennian transition. However, the processes responsible for causing the numerous anoxic events remain unclear. This study highlights the occurrence of disturbances to the phosphorus cycle during several Late Devonian crises by investigating sedimentary concentrations of the element (Ptot) as a tracer of nutrient influx, as well as its ratio with total organic carbon (TOC) to infer the recycling of the element from marine sediments. Increased TOC/Ptot ratios in the Frasnian–Famennian Lower and Upper Kellwasser horizons and upper Famennian Annulata and Hangenberg levels suggest that such nutrient recycling occurred across extensive areas of the marine shelf in Laurentia and both Rheic Ocean margins at those times, helping to sustain reducing conditions in those environments. Elevated Ptot values in the Upper Kellwasser, Annulata, and Hangenberg levels are consistent with an enhanced nutrient influx as the initial trigger for the anoxia. Correlation of phosphorus trends with other geochemical indicators of weathering/detrital influx (osmium-isotope, silicon/aluminum, and titanium/aluminium ratios) support a scenario in which terrestrial runoff provided these nutrients both to marine shelves and the oceanic inventory. Upwelling of oceanic deep-water bodies may have then brought the phosphorus to areas that had not featured major direct inputs of terrigenous material. The exception is the Lower Kellwasser Event, during which there was no increase in phosphorus delivery to marine areas and no evidence for terrestrial influx at the studied sections, invoking a different mechanism for the development of water-column anoxia. Clearly, the Late Devonian marine realm was unusually susceptible to becoming anoxic through various possible triggers, including nutrient influx from land and/or deep-water upwelling, and the recycling of phosphorus from newly deposited sediments.
Mots-clé
Phosphorus, Late Devonian, Marine anoxia, Nutrient recycling, Frasnian–Famennian extinction
Web of science
Open Access
Oui
Financement(s)
Université de Lausanne
Création de la notice
08/06/2020 16:01
Dernière modification de la notice
06/07/2024 7:05
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