An analysis of the dinoflagellates, pollen and spores occurring within the "Calcaires inférieurs " of the Lowermost Paleocene of Oraas (Pyrénées-Atlantiques) is carried out. The very diversified assemblages found at the top of the formation involve seventy species of dinoflagellates and fifty-seven species of pollen and spores. The comparison of these dinoflagellate assemblages with the other ones recorded in the world enables confirmation of the age Selandian age (D2 or base of D3) of the uppermost part of the "Calcaires inférieurs ". Two main species have been recorded: Alisocysta reticulata, restricted to the zone D2 (Costa & Manum 1988) and Spinidinium densispinatum which has its first appearance in the zone D3 of the Selandian after Powell (1992). Some obvious affinities have been shown between this phytoplankton and the Northern Europe and Northern America ones.
Dinoflagellate, pollen, Pyrénées-Atlantiques, Danian-Selandian