Foraminiferal Biostratigraphy of Well Ad, Western Niger Delta (Published)
Micropaleontological analysis of sixty (62) ditch cuttings rock samples collected from interval, 7800 feet to 12,002 feet of well AD, located offshore western Niger Delta was carried out for the investigation of their age and paleodepositional environment. Standard methods and techniques of foraminiferal sample processing and analysis were followed to disaggregate the microfauna from the rock matrix. The studied interval is predominantly made up of 80 to 100 % sandstone, minor shale and siltstone with variable textural properties. Foraminifera study revealed well preserved and diverse species dominated by the calcareous benthic forms. A total of seventy-four (74) foraminiferal species were recovered among which fifty (52) two are calcareous benthic, six (6) are agglutinating forms while sixteen (16) are planktonic foraminifera. On the basis of the faunal assemblage, abundance and diversity of the important foraminiferal events, four (4) foraminiferal zones (Valvulineria spp, Brizalina mandoroveensis, Hanzawaia concentrica and Lenticulina inornata) were recognised and correlated with F300 and F500 to assign an early to middle Miocene age for the sediments. Paleoenvironmental deductions were based primarily on the richness and diversity of foraminiferal species categories. The presence or absence of planktonic foraminifera aided in deciphering open ocean environments. The dominant biofacies associations recorded within the studied section of Well-AD is the Ammonia beccarii biofacies defined by the rare to common occurrences of Ammonia beccarii, Bolivina scalpratamiocenica, Florilus atlanticus and Epistominella vitrea. Brizalina mandoroveensis species, Lenticulina inornata, Hanzawaia strattoni, Eponides eshira, Cribroelphidium galvestonensis and Hanzawaia concentrica were also in association. The Ammonia beccarii biofacies is indicative of the Shallow/Inner Neritic Paleoenvironment, while the Inner Neritic/Middle Neritic Setting is characterized by top occurrence of Valvulineria spp, a rich continuous occurrence of Epistominella vitrea. The paleoenvironment of the studied section of Well-AD is dominantly inner to middle neritic with concomitant minor incursion of outer neritic setting.
Keywords: Age, Niger-Delta, foraminifera, micropaleontology, neritic, paleoenvironment
Palynomorph Biostratigraphy of VIC 97 Well, Nothern Depo Belt, Niger Delta, Nigeria (Published)
Palynological and sedimentological studies were conducted on sixty ditch cutting rock samples from interval 460 to 4550 feets of VIC-97 well, located at OML 38, Northern Depo-belt, Niger-Delta, to delineate lithofacies units and the age of the rock succession. Standard methods of palynological sample analysis were used to disaggregate the palynomorphs from the rock matrix. Log signatures, sand/shale ratios, textural attributes, and accessory mineal compositions of ditch cutting rock samples were used as lithologic parameters to establish two lithofacies units; the transitional unit having a sand/shale ratio of 80:20 and the continental Unit having a 98:2 ratio ascribed to upper Agbada and Benin formation respectively. Palynological analysis revealed that the retrieved palynomorphs were numerous and reasonably diversified, particularly in the lower portion of the sample interval. Palynological zonation was based on the palynofloral assemblage of important species and their stratigraphic distribution. Thirteen informal biozones were recognised on the basis of their first and last downhole occurences and compared with P 560, P580 and P624 to delineate an early to late Oligocene age for the studied interval.
Keywords: Age, Niger-Delta, lithofacies units, palynomorphs, rock