Calcareous Nannofossils Biostratigraphy and Paleoecology of Well 03, Shallow Offshore, Niger Delta, Nigeria

This study presents the calcareous nannofossils biostratigraphy of well 03, shallow offshore, Niger Delta, Nigeria using ditch cuttings samples analyzed for nannofossils to determine age, biozonation, and paleoecological interpretation. A quantity (5 g) each of the cuttings were subjected to standard smear slide preparation technique for nannofossils using Norland adhesive and the slides examined under light microscope at 1000 × magnification. Lithologically the studied sequences were composed of shale, siltstone / mudstone which are grey with intercalation of sandstones belonging to Agbada Formation. A fairly diverse 37 species of nannofossils assemblage was recovered. Two major nannofossil zones of Helicosphaera ampliaperta and Sphenolithus heteromorphus were delineated. Establishment of these zones aided the assignment of the early Miocene - late Miocene age range to the section. Paleoecology of the studied section reveals fluctuations between warm and cool climates evidenced from the variation in the assemblages of diagnostic species across the intervals, Sphenolithus heteromorphus predominates intervals 7900 – 12420 ft and the occurrence of Discoaster berggrenii between 9300 -9420 ft suggest intervals under warm climate conditions while Coccolithus pelagicus and coccolithus miopelagicus strives between 7000 -10780 ft, between 6670 -10980 ft, respectively indicating cooler environmental conditions.