Formal and Informal Foraminiferal Biozonation Framework for Tertiary Sedimentary Succession in F-Well, Niger Delta

Abstract

Foraminiferal biozonation of tertiary sediments in F-Well Niger Delta were carried out with the aim of establishing a formal and informal biozones. Fifty (50) ditch cutting samples, sampled at varying intervals were used to establish the biozonation framework for the studied intervals. A total of eighty (80) foraminiferal species were recorded, most of the species recorded are calcareous and arenaceous benthic foraminiferal species. Two planktic zones ( N4-N3 and N3 – N2 ) and nine informal assemblage zones ranging from A to I were established. N4-N3 Planktic zone has a reference interval of 8,000ft – 9,400ft. The top of this zonal interval which ought to be marked by the FDO of Ammonia becarril was absent but was estimated to be 8,000 ft. The base of this zonal interval is marked by the LDO of Epistominellavitriea at 9,400 ft. N3 – N2 Planktic zone has a reference interval of 9,400ft – 10,000 ft. The top of this zonal interval is marked by the FDO of Bolivina imperatrix at 9,400 ft. The base of this zonal interval is marked by the LDO of Spirosplectaminawrightii at 10,000 ft. The presence of twenty-eight (28) diagnostic species aided in establishing nine informal biozones. These are Haplophragmoidesspassemblage zone A, Bathysiphon sp. Assemblage zone B, Trochamminaspassemblage zone C, Ammobaculitesspassemblage zone D, Arenaceous indeterminate assemblage zone E, Uvigerinasparsicostata assemblage zone F, Haplophragmoidesnarivaensisassemblage zone G, Epistominellavitrieaassemblage zone H and Cassigerinellachipollensisassemblage zone I.