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The Early Toarcian oceanic anoxic event: Paleoenvironmental and paleoclimatic change across the Alpine Tethys (Switzerland)

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Fantasia, Alicia et Föllmi, Karl B. et Adatte, Thierry et Spangenberg, Jorge E. et Montero-Serrano, Jean-Carlos (2018). The Early Toarcian oceanic anoxic event: Paleoenvironmental and paleoclimatic change across the Alpine Tethys (Switzerland). Global and Planetary Change, 162 . p. 53-68.

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Résumé

Paleoenvironmental and paleoclimatic change associated with the Toarcian oceanic anoxic event (T-OAE) was evaluated in five successions located in Switzerland. They represent different paleogeographic settings across the Alpine Tethys: the northern shelf (Gipf, Riniken and Rietheim), the Sub-Briançonnais basin (Creux de l'Ours), and the Lombardian basin (Breggia). The multi-proxy approach chosen (whole-rock and clay mineralogy, phosphorus, major and trace elements) shows that local environmental conditions modulated the response to the T-OAE across the Alpine Tethys. On the northern shelf and in the Sub-Briançonnais basin, high kaolinite contents and detrital proxies (detrital index, Ti, Zr, Si) in the T-OAE interval suggest a change towards a warmer and more humid climate coupled with an increase in the chemical weathering rates. In contrast, low kaolinite content in the Lombardian basin is likely related to a more arid climate along the southern Tethys margin and/or to a deeper and more distal setting. Redox-sensitive trace-element (V, Mo, Cu, Ni) enrichments in the T-OAE intervals reveal that dysoxic to anoxic conditions developed on the northern shelf, whereas reducing conditions were less severe in the Sub-Briançonnais basin. In the Lombardian basin well-oxygenated bottom water conditions prevailed. Phosphorus (P) speciation analysis was performed at Riniken and Creux de l'Ours. This is the first report of P speciation data for T-OAE sections, clearly suggesting that high P contents during this time interval are mainly linked to the presence of an authigenic phases and fish remains. The development of oxygen-depleted conditions during the T-OAE seems to have promoted the release of the organic-bound P back into the water column, thereby further sustaining primary productivity in a positive feedback loop. -- Keywords : Toarcian OAE ; Proximal-distal transect ; Mineralogy ; Geochemistry ; Phosphorus ; Climate change.

Type de document : Article
Validation par les pairs : Oui
Mots-clés : Evenement Anoxique Oceanique Toarcien Tethys Alpine Suisse Mineralogie Geochimie Paleoenvironnement Paleoclimat Paleogeographie
Départements et unités départementales : Institut des sciences de la mer de Rimouski (ISMER)
Déposé par : DIUQAR UQAR
Date de dépôt : 13 janv. 2020 19:30
Dernière modification : 13 janv. 2020 19:30
URI : http://semaphore.uqar.ca/id/eprint/1556

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