Programme des sessions > Par intervenant > Gaspard Daniele

Brachiopods are present since the Cambrian, although decreasing after the permo-triassic period with a heavy replacement of taxa, they are still present during the Mesozoic and particularly during the Cretaceous, even the Campanian. 

After the reports of Coquand (1958-62) in a restricted region of the stratotype (Aubeterre), Arnaud (1877) tried to precise the boundaries of the Campanian highlighting the basal part by the first occurrence of (Cyclothyris (Rhynchonella) globata (Arnaud, 1877)) in his sublevel (P1). However, misinterpretations remained for the upper part of the Campanian there. The works of Seronie-Vivien (1972-76), those of Andrieff & Marionnaud (1973) providing a biozonation based on benthic foraminifera, followed by Neumann et al. (1883) and the geologic maps of Platel (1976-1996) allowed to precise the upper limit of the Campanian in les Charentes and Dordogne. 

Two subphyla of the phylum Brachiopoda (Rhynchonelliformea (e.g. Articulata) and Craniiformea (e.g. Inarticulata pr.p.) are recognized in this stratopype region. Representatives of about twenty species were recognized by their external (morphology and ornamentation) and internal (shape of brachidium using transverse serial sections, microtomography and when available, owing to diagenesis, microstructural characteristics. These identified species [a Craniida; Rhynchonellida, Thecideida, Terebratulida (Terebratulidina and Tetebratellidina)], are repositioned within the nine biozones (Andreieff and Marionnaud, 1973), and six formations (Fm: Gimeux, Segonzac, Biron, Barbezieux, Aubeterre, Maurens) proposed by Platel (1996, 1999 and Contribution to the volume of the Campanian Stratotype in progress). The Campanian series ends with tufa limestones with a Thecidea sp .and "Waldheimia" clementi Coquand of the Maurens formation. The evolution of these Campanian species (some of which were already present as early as the Santonian) is highlighted in various environmental facies of the North Aquitaine platform from a deep marine environment (Lower Campanian) via progressively a circa, an infralittoral platform. (Upper Campanian) to a nearly costal environment.