Rapid light carbon releases and increased aridity linked to Karoo-Ferrar magmatism during the early Toarcian oceanic anoxic event

• Published in: Scientific Reports
• Main Authors: Font, Eric, Duarte, Luís Vítor, Dekkers, Mark J., Remazeilles, Celine, Egli, Ramon, Spangenberg, Jorge E., Fantasia, Alicia, Ribeiro, Joana, Gomes, Elsa, Mirão, José, Adatte, Thierry
• Other Authors: Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Ingénieur pour l'Environnement - UMR 7356 (LaSIE), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU]Sciences of the Universe [physics]; Methane hydrate
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03691309; https://hal-insu.archives-ouvertes.fr/insu-03691309/document; https://hal-insu.archives-ouvertes.fr/insu-03691309/file/s41598-022-08269-y.pdf; https://doi.org/10.1038/s41598-022-08269-y

International audience Large-scale release of isotopically light carbon is responsible for the carbon isotope excursion (CIE) of the Toarcian Oceanic Anoxic Event during the Lower Jurassic. Proposed sources include methane hydrate dissociation, volcanogenic outgassing of carbon dioxide and/or thermogenic methane release from the Karoo-Ferrar magmatic province (southern Africa). Distinct small-scale shifts superimposed on the long-term CIE have been interpreted as rapid methane pulses linked to astronomically forced climate changes. In the Peniche reference section (Portugal), these small-scale shifts correspond to distinct brownish marly layers featuring markedly high mercury (Hg) and magnetic mineral concentration. Total organic carbon and Hg increase are uncorrelated, which suggests input of Hg into the atmosphere, possibly released after the intrusion of the Karoo-Ferrar sills into organic-rich sediments. Enhanced magnetic properties are associated with the presence of martite, washed-in oxidized magnetite, inferred to be due to increased aridity on the continental hinterland. This study provides strong evidence for a direct link between the Karoo-Ferrar magmatism, the carbon-isotope shifts and the resulting environmental changes.