Réponse des communautés de conodontes aux perturbations eustatiques : ees événements fini-dévoniens dans la Montagne Noire (France)

Abstract

Abundance and generic diversity tendencies of conodont communities have been studied across the Upper Kellwasser and the Hangenberg events, which correspond respectively to the Frasnian/Famennian and the Devonian/Carboniferous boundaries, in the Montagne Noire, stratotypic area of these two boundaries. Conodont communities evolution shows that these two events can be characterized by a succession of rapid eustatic variations, transgressive before and after the event and regressive during the event. However, detailed studies indicate that, on the one hand, the depth variations modify the communities composition, and on the other hand, induce mass extinctions known for these two boundaries. Each bathymetric change is characterized by a decrease of conodont number, but it seems that it is the transgressive-regressive couplet which is the cause of an abundance decrease without diversity modification, whereas regressive-transgressive couplet would provoke mass extinctions.