Occurrence of some Maastrichtian dinoflagellate cysts from the upper cretaceous sediments of the Bida Basin, Nigeria: implications for age and paleoenvironments.

Abstract

Lithostratigraphic and palynological studies of the shale facies of the upper Cretaceous Patti Formation, southeastern Bida Basin, Nigeria have allowed the determination of the paleoenvironment and age of the sediments. Marine dinocysts assemblage and terrestrial pollen and spores (relatively more abundant) are well preserved in the sections. The marine dinocysts include diverse species of the genera Dinogymnium, Senegalinium, Andalusiella and Spiniferites. This assemblage reflects influence of shallow marine process during sedimentation of the shales and they provide, for the first time, incontrovertible evidence of the presence of marine condition in southeastern part of the Bida Basin. A Maastrichtian age is suggested for the Shale facies of the Patti Formation in the study area based on the occurrence of well known Maastrichtian marine dinoflagellates Dinogymnium acuminatum, Dinogymnium digitus, Senegalinium bicavatum, Senegalinium psilatum and Paleocystodinium australinium. Associated with these forms also are some Maastrichtian spores and pollen; Buttinia andreevi, Cristaeturites cristatus, and Retidiporites magdalenensis. This study therefore, is considered significant as it also confirms marginal marine connection between the Anambra and Bida basins and consequently is a proof that the later formed a part of the links between the Tethys sea and the south Atlantic sea in the Maastrichtian time.

KEY WORDS: Bida Basin, Patti Formation, Maastrichtian