Chitinozoan Bio-event in the Frasnian–Famennian Boundary Beds at La Serre (Montagne Noire, Southern France)

Chitinozoans and other palynomorphs have been investigated in Frasnian–Famennian boundary beds from trench C at La Serre (Montagne Noire, Southern France). This lithology proves to be more suitable for palynological investigations than the reddish nodular limestones of the F–F stratotype in the Coumiac section, which are virtually devoid of organic matter. At La Serre, the most basal Famennian bed yields an exceptional number of chitinozoans (up to 19,000 specimens per gram of rock), a few tracheids, but virtually no Tasmanaceans. The relationships between the anomalous abundance of chitinozoans and the latest Frasnian–earliest Famennian mass extinction are documented, and it is concluded that the exceptional chitinozoan concentration is related to a temporary increase in the hydrodynamic energy at the water–sediment interface.