Apport de données palynologiques à la reconstruction paléoenvironnementale de l’Albo-Cénomanien des Charentes (Sud-Ouest de la France)

Abstract

Palynological contributions for the palaeoenvironmental reconstruction of the Albo-Cenomanian from the Charentes (SW France). The Albo-Cenomanian deposits from the Charentes region (SW France) are characterized by the strong development of brackish and estuarine facies with amberiferous lignitic clays and sands. These facies, which occur in six localities previously studied from a sedimentological and macropalaeontological point of view, exhibit well-preserved palynological assemblages. The studied samples have yielded assemblages dominated by pollen grains of conifers of the genera Araucariacites, Classopollis and Inaperturopollenites, as well as fern spores of Gleicheniaceae and Schizaeaceae. The presence of pollen grains of primitive angiosperms is remarkable in Upper Albian and Lower Cenomanian samples. Furthermore, genus Complexiopollis, which belongs to the Normapolles Group, has been identified in the Upper Cenomanian sample. The picture of the vegetation of the Charentes was determined by two types of coniferous forests. On the one hand, the coastal areas were inhabited by xerophytic trees belonging to the Cheirolepidiaceae, with a rich undergrow constituted by bennettitales, cycads and ferns of the families Gleicheniaceae and Schizaeaceae. On the other hand, open formations of Araucariaceae and Cupressaceae developed in wetter places presenting an understory mainly integrated by ferns. A third plant community composed of ginkgoales in association with primitive angiosperms could develop in riparian places. The studied palynoflora has similarities with other ones from Provence, Vendée, Aquitaine, and Sarthe. This study presents the first reconstruction of palaeovegetation biodiversity and changes between the Uppermost Albian and the basal Upper Cenomanian in the Charentes (SW France). Pour citer cet article : D. Peyrot et al., C. R. Palevol 4 (2005) .