Abstract

The Early Jurassic was marked by several episodes of rapid climate change and environmental perturbation. These changes culminated during the Toarcian Oceanic Anoxic Event (T-OAE), an episode of global warming that led to the widespread deposition of organic-rich shales. The Toarcian shales of NW Europe have also yielded exceptionally preserved fossils of marine vertebrates and invertebrates, but the potential links between the occurrences of these exceptionally preserved fossils and the T-OAE remain poorly investigated. Palaeontological excavations realized in Toarcian strata near Lodève (Hérault, southern France) have yielded several specimens of marine vertebrates and abundant invertebrate fauna. We have developed a multiproxy approach (ammonite biostratigraphy, X-ray diffraction-bulk mineralogy, Rock-Eval pyrolysis, stable isotopes, trace element, phosphorus and mercury contents) to place these findings in a well-defined temporal and palaeoenvironmental context, and hence constrain the factors that led to their remarkable preservation. The Jenkyns Event interval, unambiguously identified at the base of the Toarcian organic-rich shales by a 5‰ negative carbon isotope excursion, records higher mercury fluxes, which suggest a causal link with intense volcanic activity of the Karoo–Ferrar large igneous province. This interval is very condensed and unfossiliferous, and might have been deposited under abnormally low-salinity conditions. Our data show that the deposition of the vertebrate-yielding horizons post-dated the T-OAE by several hundreds of ka, and took place during a prolonged period of widespread oxygen-deficiency and elevated carbon burial. Our results indicate that the unusual richness in vertebrates of the studied site can be explained by a combination of regional factors such as warming-induced, prolonged seafloor anoxia, and more local factors, such as extreme condensation owing to reduced dilution by carbonate and detrital input.

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Author contributions

BB: conceptualization (equal), data curation (lead), formal analysis (lead), funding acquisition (lead), investigation (lead), methodology (lead), resources (equal), software (equal), validation (lead), visualization (lead), writing – original draft (lead), writing – review & editing (lead); GS: conceptualization (equal), data curation (equal), formal analysis (equal), funding acquisition (supporting), investigation (equal), methodology (supporting), resources (equal), software (supporting), validation (equal), visualization (equal), writing – original draft (equal), writing – review & editing (equal); JS: data curation (equal), formal analysis (equal), funding acquisition (supporting), investigation (supporting), validation (supporting), writing – review & editing (supporting); A-SG: formal analysis (supporting), project administration (supporting), visualization (supporting), writing – review & editing (equal); BS-M: data curation (supporting), formal analysis (supporting), investigation (supporting), project administration (equal), validation (equal), visualization (equal), writing – review & editing (equal); TA: data curation (supporting), formal analysis (equal), funding acquisition (equal), investigation (supporting), methodology (equal), resources (supporting), validation (supporting), writing – review & editing (equal); JES: data curation (equal), formal analysis (equal), methodology (equal), validation (supporting), writing – review & editing (equal); SF: funding acquisition (equal), project administration (equal), validation (supporting), writing – review & editing (supporting); AZ: project administration (supporting), writing – review & editing (supporting); CG: project administration (supporting), writing – review & editing (supporting); J-MB: project administration (supporting), validation (supporting), visualization (supporting), writing – review & editing (supporting); VP: project administration (supporting), validation (supporting), visualization (supporting), writing – review & editing (supporting); PV: conceptualization (supporting), funding acquisition (equal), project administration (equal), validation (supporting), visualization (supporting), writing – review & editing (supporting); KJ: funding acquisition (supporting), project administration (equal), writing – review & editing (supporting); JEM: conceptualization (supporting), funding acquisition (equal), project administration (lead), validation (equal), writing – review & editing (supporting).

Funding

The field campaigns were partly supported by the ANR Oxymore (ANR-18-CE31-0020) and the Lodévois and Larzac Community of Municipalities. The fieldwork of JS was partly financed from projects APVV 17-0555 and VEGA 2/0169/19, and the laboratory analyses were supported by the University of Lausanne.

Data availability

All data generated or analysed during this study are included in this published article (and its supplementary information files).

Information & Authors

Information

Published In

cover image Geological Society, London, Special Publications
Special Publications
Volume 5142021
Pages: 121 - 152

History

Published: 2021
Received: 24 January 2021
Revision received: 8 July 2021
Accepted: 9 July 2021
Published online: 17 September 2021

Authors

Affiliations

Institute of Earth Sciences, University of Lausanne, Geopolis, CH-1015 Lausanne, Switzerland
Author Contributions: [Conceptualization (Equal)], [Data curation (Lead)], [Formal analysis (Lead)], [Funding acquisition (Lead)], [Investigation (Lead)], [Methodology (Lead)], [Resources (Equal)], [Software (Equal)], [Validation (Lead)], [Visualization (Lead)], [Writing – original draft (Lead)], and [Writing – review & editing (Lead)].
Guillaume Suan
Université de Lyon, UCBL, ENSL, CNRS, UMR 5276 LGL-TPE, 69622 Villeurbanne, France
Author Contributions: [Conceptualization (Equal)], [Data curation (Equal)], [Formal analysis (Equal)], [Funding acquisition (Supporting)], [Investigation (Equal)], [Methodology (Supporting)], [Resources (Equal)], [Software (Supporting)], [Validation (Equal)], [Visualization (Equal)], [Writing – original draft (Equal)], and [Writing – review & editing (Equal)].
Jan Schlögl
Department of Geology and Paleontology, Comenius University, Mlynska dolina G, 84215, Bratislava, Slovakia
Author Contributions: [Data curation (Equal)], [Formal analysis (Equal)], [Funding acquisition (Supporting)], [Investigation (Supporting)], [Validation (Supporting)], and [Writing – review & editing (Supporting)].
Anne-Sabine Grosjean
Paleorhodania, 69006 Lyon, France
Author Contributions: [Formal analysis (Supporting)], [Project administration (Supporting)], [Visualization (Supporting)], and [Writing – review & editing (Equal)].
Aix Marseille Univ, CNRS, IRD, INRAE, Coll France, CEREGE, Aix-en-Provence, France
Author Contributions: [Data curation (Supporting)], [Formal analysis (Supporting)], [Investigation (Supporting)], [Project administration (Equal)], [Validation (Equal)], [Visualization (Equal)], and [Writing – review & editing (Equal)].
Institute of Earth Sciences, University of Lausanne, Geopolis, CH-1015 Lausanne, Switzerland
Author Contributions: [Data curation (Supporting)], [Formal analysis (Equal)], [Funding acquisition (Equal)], [Investigation (Supporting)], [Methodology (Equal)], [Resources (Supporting)], [Validation (Supporting)], and [Writing – review & editing (Equal)].
Institute of Earth Surface Dynamics, University of Lausanne, Geopolis, CH-1015 Lausanne, Switzerland
Author Contributions: [Data curation (Equal)], [Formal analysis (Equal)], [Methodology (Equal)], [Validation (Supporting)], and [Writing – review & editing (Equal)].
Stéphane Fouché
Musée de Lodève, 1 place Francis Morand, 34700, Lodève, France
Author Contributions: [Funding acquisition (Equal)], [Project administration (Equal)], [Validation (Supporting)], and [Writing – review & editing (Supporting)].
PALEVOPRIM Laboratoire Paléontologie Evolution Paléoécosystèmes Paléoprimatologie UMR CNRS 7262, Université de Poitiers, 86073 Poitiers Cedex 9, France
Author Contributions: [Project administration (Supporting)] and [Writing – review & editing (Supporting)].
PALEVOPRIM Laboratoire Paléontologie Evolution Paléoécosystèmes Paléoprimatologie UMR CNRS 7262, Université de Poitiers, 86073 Poitiers Cedex 9, France
Author Contributions: [Project administration (Supporting)] and [Writing – review & editing (Supporting)].
Jean-Michel Brazier
Institute of Applied Geosciences, Graz University of Technology, Rechbauerstrasse 12, A-8010 Graz, Austria
Author Contributions: [Project administration (Supporting)], [Validation (Supporting)], [Visualization (Supporting)], and [Writing – review & editing (Supporting)].
Vincent Perrier
Université de Lyon, UCBL, ENSL, CNRS, UMR 5276 LGL-TPE, 69622 Villeurbanne, France
Author Contributions: [Project administration (Supporting)], [Validation (Supporting)], [Visualization (Supporting)], and [Writing – review & editing (Supporting)].
Peggy Vincent
Sorbonne Université (CNRS-MNHN-UPMC) – Muséum national d'Histoire naturelle, Département Origines et Evolution, UMR CNRS-MNHN-UPMC 7207, Centre de Recherche en Paléontologie-Paris, 57, rue Cuvier – 75231 Paris Cedex 05, France
Author Contributions: [Conceptualization (Supporting)], [Funding acquisition (Equal)], [Project administration (Equal)], [Validation (Supporting)], [Visualization (Supporting)], and [Writing – review & editing (Supporting)].
Kévin Janneau
Université de Strasbourg (UNISTRA), Jardin des sciences, 12 Rue de l'Université, 67000 Strasbourg, France
Author Contributions: [Funding acquisition (Supporting)], [Project administration (Equal)], and [Writing – review & editing (Supporting)].
Jeremy E. Martin
Université de Lyon, UCBL, ENSL, CNRS, UMR 5276 LGL-TPE, 69622 Villeurbanne, France
Author Contributions: [Conceptualization (Supporting)], [Funding acquisition (Equal)], [Project administration (Lead)], [Validation (Equal)], and [Writing – review & editing (Supporting)].

Notes

*
Correspondence: [email protected]

Funding Information

ANR-18-CE31-0020
APVV 17-0555
VEGA 2/0169/19
University of Lausanne

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  • The Toarcian Oceanic Anoxic Event: where do we stand?, Geological Society, London, Special Publications, 10.1144/SP514-2021-74, 514, 1, (1-11), (2021).

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