FORAMINIFERA BIOZONATION OF "WELL K-27", GREATER UGHELLI DEPOBELT, NIGER DELTA BASIN, SOUTH EASTERN NIGERIA

ABSTRACT

Ditch cutting samples collected from interval 2590 3300 metres in Well K-27, Greater Ughelli depobelt, Niger Delta were studied for their lithology and foraminiferal content with the aim of dating and subdivision of the sequences penetrated by the well into biozones. The samples were processed using standard foraminiferal processing methods involving sample disaggregation and washing through a 63 micron mesh sieve, drying and picking and subsequent analysis of the foraminifera and accessory fauna. Results showed that the well section penetrated the   alternating sand and shale sequence of the Agbada Formation and yielded characteristic benthic foraminifera markers such as Hopkinsina bononiensis, Spiroplectammina wrightii, Uvigerinella sparsicostata, Lenticulina grandis and Bolivina imperatrix which corresponds to P18-P19, P20/N1, P21/N2 and P22/N3 foraminiferal zones and were used to assign an Early Oligocene to Late Oligocene and younger ages for the well. Four foraminiferal zones were identified viz: Globigerina selli/pseudohastigerina barbadoensis zone (P18-P19), Globigerina ampliapertura zone (P20/N1), Globorotalia opima opima zone (P21/N2) and Globigerina ciperoensis ciperoensis zone (P22/N3). These biozones can be useful in the dating and correlation of large rock units of same geologic age. KEYWORDS: Foraminifera, Oligocene, Biozone, Greater Ughelli depobelt, Niger Delta.