Similarities between the microflora of the Alter do Chão Formation, Amazonas Basin and the Barreirinhas Basin allow the comparison of the taxonomic entities of these basins. Nine palynomorphs, from wells NO-1-AM (Nova Olinda), and AC-1-PA (Alter do Chão), were selected and compared with recent papers of Lima (1971) and Herngreen (l973), from the Barreirinhas Basin. The conclusion arrived was that the Alter do Chão Formation sedimentation, in the examined area, developed in the Cretaceous, Middle Albian, Cenomanian and Turonian.Similarities between the microflora of the Alter do Chão Formation, Amazonas Basin and the Barreirinhas Basin allow the comparison of the taxonomic entities of these basins. Nine palynomorphs, from wells NO-1-AM (Nova Olinda), and AC-1-PA (Alter do Chão), were selected and compared with recent papers of Lima (1971) and Herngreen (l973), from the Barreirinhas Basin. The conclusion arrived was that the Alter do Chão Formation sedimentation, in the examined area, developed in the Cretaceous, Middle Albian, Cenomanian and Turonian.