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

Abstract

The present study based on the lithostratigraphic and palynological analyses of the shale facies of the upper Cretaceous Patti Formation, southeastern Bida Basin, Nigeria was carried out with the aims of determining the paleoenvironment and age of the sediments from the point of view of microfloral data. 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 the sedimentation of the shales and they provide, for the first time, incontrovertible evidence of presence of marine condition in southeastern part of the Bida Basin. The data therefore, is considered significant as it confirms marginal marine connection between the Anambra basin and Bida basins and consequently, the Bida Basin forms part of the links between the Tethys sea and the south Atlantic sea in the Maastrichtian time. 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.