Lithostratigraphic and calcareous nannofossil biostratigraphic studies was carried out on ditch cutting samples from well - AD1X located in the offshore area of the Niger Delta. The Agbada Formation sediments are made up of shales and sandstones which are grey in colour with intercalations of fine to medium grained sandstone beds. The sediments yielded relatively rich calcareous nannofossils with significant variations in abundance and diversity. Some Niger Delta index fossils present in the study include; Discoaster pentaradiatus, Amaurolithus delicatus, Discoaster asymmetricus, Discoaster quinqueramus and Helicosphaera sellii. Late Miocene to Early Pliocene age was assigned to the studied well based on the occurrences of these index fossils, while a shallow marine environmental condition of deposition was suggested due to the rich diversity of nannofossils.