Quistos de dinoflagelados do Cenomaniano médio da Nazaré: Paleoambientes e implicações biostratigráficas

The post-rift Upper Cretaceous stratigraphic succession of Portugal contains the Western Portuguese Carbonate Platform which stands out as an extensive marine succession. This Carbonate platform is middle Albian to early Turonian in age, contemporary of eustatic highstands and widespread flooding of the European and North African continental margins of the Tethys Sea. A thick fossil-rich carbonate succession outcrops in the Nazaré promontory where middle Cenomanian organic-rich lagoonal facies are exposed. The palynological study performed in these facies revealed the presence of a diverse assemblage of dinoflagellate cysts (dinocysts) composed of Subtilisphaera sp., Xenascus sp., Sentusidinium group and Florentinia sp., several dinocyst taxa considered new to the Portuguese Cretaceous. Moreover, this study provides significant biostratigraphic and palaeoenvironmental data. The dinocyst associations suggest the existence of a marginal-lagoonal environment, located nearby an inner shelf carbonated platform, and affected by fine-grained influxes from nearby fluvial drainage.