Palaeoecological Aspects of Nannoplankton Assemblages of AS-2 Well, Niger Delta

Abstract

Certain nannoplankton species are sensitive to surface water conditions hence, they are proxy for palaeocological studies. This study analyzed biostratigraphy and inferred paleoecologic preferences of major nannofossil species of ditch cutting samples from well AS-2, Niger delta.  The relative fluctuation and changes in abundance of the nannoplankton allowed the following deductions in the study interval: Two major biozones, NP21 and NP20 of late Eocene (Priabonian) and early Oligocene (Rupelian). Higher abundances of Reticulofenestra  spp (49% ) compared to the total taxa recovered, including Cyclicargolithus spp, Coccolithus spp and Chiasmolithus spp were characterized as cool water, eutrophic conditions while  Sphenolithus spp, Helicosphaera spp, Pontosphaera spp were characterize as warmer water more Oligotrophic species. The total increase in abundance of cooler-water indicators over the warm-water forms within the study intervals suggest a prevailing environmental condition describing cooler water trends, eutrophic and upwelling ones with nutrient rich conditions during the Oligocene period than in the Eocene.