TY - CHAP
T1 - The palaeoenvironmental context of toarcian vertebrate-yielding shales of southern france (Hérault)
AU - Bomou, Brahimsamba
AU - Suan, Guillaume
AU - Schlögl, Jan
AU - Grosjean, Anne Sabine
AU - Suchéras-Marx, Baptiste
AU - Adatte, Thierry
AU - Spangenberg, Jorge E.
AU - Fouché, Stéphane
AU - Zacaï, Axelle
AU - Gibert, Corentin
AU - Brazier, Jean Michel
AU - Perrier, Vincent
AU - Vincent, Peggy
AU - Janneau, Kévin
AU - Martin, Jeremy E.
N1 - Funding Information:
Funding The field campaigns were partly supported by the ANR Oxymore (ANR-18-CE31-0020) and the Lodé-vois and Larzac Community of Municipalities. The field-work 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.
Publisher Copyright:
© 2021 The Author(s).
PY - 2021
Y1 - 2021
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85118994063&partnerID=8YFLogxK
U2 - 10.1144/SP514-2021-16
DO - 10.1144/SP514-2021-16
M3 - Chapter
AN - SCOPUS:85118994063
T3 - Geological Society Special Publication
SP - 121
EP - 152
BT - Geological Society Special Publication
PB - Geological Society of London
ER -
