Synthesis of the palynological content of the Lower Cretaceous continental deposits in France: stratigraphic and palaeoenvironmental implications

International audienceA first attempt at a biostratigraphic synthesis of the palynological content of French Lower Cretaceous continental deposits is the subject of this paper. Palynomorphs listed in previous studies on Berriasian–Albian non-marine palynology have been taken into account, gathering 360 species of pollen grains and spores altogether. In addition, 70 samples have been recovered from outcrops of argillaceous rocks, mostly corresponding to the Purbeck and Wealden facies of southern England. The samples concerned are from the departments of Charente-Maritime, Charente, Savoie (Berriasian, Valanginian, Albian), Oise, Seine-Maritime, Pas-de-Calais (Hauterivian–Barremian), and Isère (Aptian). Early Cretaceous miospores are commonly long-ranging; hence, it is necessary to consider fluctuations in their abundance within palynological assemblages if they are to have any biostratigraphic value. Lower Berriasian assemblages are often dominated by gymnosperm pollen grains, associated with anemiaceous spores such as Cicatricosisporites australiensis and C. hughesii. These taxa are also found in younger strata, but upper Berriasian–Valanginian assemblages are characterized by containing more abundant lygodiaceous verrucate spores associated with the appearance of gleicheniaceous Clavifera triplex from the Valanginian onwards. Many genera have been erected to accommodate Mesozoic verrucate spores. The considerable overlap between diagnoses diminishes the stratigraphic significance of the constituent species. Only the genera Concavissimisporites and Trilobosporites are considered useful here. Hauterivian–Barremian assemblages are similar to those of the Valanginian, but differ in the reduction in numbers of verrucate spores and a commensurate increase in abundance of Cicatricosisporites and Appendicisporites associated with the first occurrences of monoaperturate angiosperm pollen grains, such as Clavatipollenites hughesii, within Barremian deposits of northern France. Considered to be more typical of Albian assemblages, Clavatipollenites rotundus has been recovered from lower Aptian deposits in south-eastern France. Aptian palynofloras arealso characterized by the appearance of other monoaperturate pollen forms, such as Retimonocolpites. Very little information is available on French Albian assemblages. They are defined by the diversification of dicotyledonous tri– and polyaperturate pollen grains associated with the virtual disappearance of lygodiaceous verrucate spore