RT Journal Article
T1 Seawater temperature and carbon isotope variations inbelemnites linked to mass extinction during the Toarcian(Early Jurassic) in Central and Northern Spain.Comparison with other European sections
A1 Gómez Fernández, Juan José
A1 Goy Goy, Antonio
A1 Canales Fernández, María Luisa
AB The Early Toarcian mass extinction marks one of the critical events in the history of the Earth. Many of these events have beenlinked to important climate changes. Two sections of the Toarcian showing high-resolution ammonite-based biostratigraphy arestudied in Central and Northern Spain. Stable isotope datasets, based on the analysis of 192 diagenetically screened belemnitecalcite and 41 bulk carbonates, allowed the construction of δ13C curves and a δ18O-based palaeotemperature. Comparison of theextinction pattern with other sections in Europe and northern Africa shows that the Early Toarcian mass extinction boundaryoccurred at the Tenuicostatum–Serpentinum transition, and that the organic-rich facies linked to the Oceanic Anoxic Event and theassociated negative δ13C excursion are diachronous.From a latest Pliensbachian cooling interval, a first increment of seawater temperature averaging about 4.5 °C, started aroundthe Pliensbachian–Toarcian boundary and developed during the earliest Toarcian Tenuicostatum Biochron, marking the beginningof the main extinction interval. From the Tenuicostatum–Serpentinum transition up to the Bifrons Biochron, a rise in seawatertemperature averaging 5.7 °C to 7.8 °C was recorded. This warming interval, which started rapidly and which seems to besynchronous at least in Western Europe, is considered one of the main factors responsible for mass extinction. For some authorsthis rapid warming was probably due to a massive injection of greenhouse gases into the atmosphere, but it does not seem to berecorded in belemnite calcite, and the origin of these possible gases is largely debated in the literature.Additional isotope excursions were found in the studied sections in Spain during the Middle and Late Toarcian. A negativeδ13Cbel excursion has been recorded at the latest Bifrons Biochron. Above this shift, the Illustris–Vitiosa subzones thermal peak,which represents a 2–3 °C ΔT, could be linked to one of the tectonomagmatic activity peaks recorded in the Karoo Basin. Arenewal in the ammonite and brachipod faunas coincident with this climatic change has been recognized in NW Europe andWestern Tethys.An interesting thermal peak has also been detected in belemnites of the Insigne Subzone. ΔT is in the order of 3 °C, and in bothsections the thermal peak is included into a δ13Cbel negative excursion of about −1.5‰. Relative synchrony with the new age forthe Karoo main magmatic activity (178–180 Ma) indicates that the δ13C negative anomaly and the warming interval could becaused by the release of volcanogenic greenhouse gases. At this short interval, noteworthy changes in the abundance and diversity of the recorded assemblages in several faunal groups of NW Europe and Tethys are observed. The uppermost Levesquei Subzonethermal peak has only been recognized in the deposits of the section located in Central Spain and coincides with a positive δ13Cexcursion.
PB Elsevier
SN 0031-0182
YR 2008
FD 2008
LK https://hdl.handle.net/20.500.14352/49567
UL https://hdl.handle.net/20.500.14352/49567
LA eng
DS Docta Complutense
RD 9 abr 2025