Changements climatiques, cycle du carbone et production carbonatée au Pliensbachien-Toarcien
Auteur / Autrice : | Guillaume Suan |
Direction : | Bernard Pittet, Christophe Lecuyer, Emanuela Mattioli |
Type : | Thèse de doctorat |
Discipline(s) : | Stratigraphie |
Date : | Soutenance en 2008 |
Etablissement(s) : | Lyon 1 |
Mots clés
Résumé
The relationships between changes in climate, carbon cycling and carbonate production in the Pliensbachian-Toarcian are investigated using geochemical, sedimentological and paleontological data acquired in Portugal, Italy and northern Siberia. Reconstructions of seawater temperatures inferred from the oxygen isotope composition of brachiopod shells reveal successive and marked cooling and warming episodes. The analysis of calcareous nannofossils and carbonate contents indicate that warming episodes corresponded to drastic carbonate production decline and extinction in both neritic and pelagic settings. Global variations in carbon isotope ratios indicate that warming events were probably controlled by atmospheric CO2 concentrations, likely caused by episodes of intense volcanism in South Africa and in Antarctica