Biostratigraphy of Ochigbo–1 Well, Offshore Niger Delta; Evidence from Foraminifera, Spores and Pollen

Abstract

This study involved the palynological and micropalaeontological studies of Ochigbo – 1 well, offshore Niger Delta. A total of Sixty-two (62) ditch cutting samples were composited at intervals of 100 ft covering a total depth of 7,235 ft (3,405-10,640 ft). The samples were subjected to standard procedure for palynological and micropalaeontological studies. The recovered palynomorph and the foraminiferal assemblages were rich over the intervals and were generally good to moderate, both diverse and well preserved. The recovered palynomorphs were used in establishing four palynological zones. These are: Crassoretitriletes vanraadshooveni/P700 Zone characterized by the quantitative base occurrence of Crassoretitriletes vanraadshooveni and co-occurrence of Belskipollis elegans, Crassoretitriletes vanraadshooveni, Echiperiporites estalae, and Verrutricolporites rotundiporus; dated Middle Miocene; Magnastriatites  howardii/P600  Zone  characterized  by  quantitative  base  occurrence  of  Peregrinipollis nigericus and co-occurrence of Praedapollis flexibilis, Magnastriatites  howardii  and Monoporites annulatus; dated Early Miocene – Late Oligocene; Retibrevitricolporite obodoensis/protudens/P500 Zone characterized by the co-occurrence of Arecipites exilimuratus, Retibrevitricolporite obodoensis/protudens, Verrucatosporites usmensis and Gemmamonoporites sp dated Late – Early Oligocene and Racemonocolpites hians/P400 Zone characterized by the base occurrence of Racemonocolpites hians. The recovered foraminferal assemblages revealed the well to have penetrated through the N16-N15 (Uvigerina subperegrina) Zone (Late – Middle Miocene), N15-N14 (Spirosigmolina oligocaenica) Zone; dated Middle Miocene; N13-N11(Uvigerina sparsicostata) Zone; dated Middle Miocene; N5-N4 (Megastomella africana) Zone: dated Early Miocene; N2 (Spiroplectammina wrightii) Zone; dated Late Oligocene;P18-P15 (Hopkinsinna bononiensis) Zone; dated Early Oligocene; P14-P12 (Uvigerina hourqi) Zone; dated Late Eocene; P12 (Uvigerina havanensis) Zone; dated Late – Middle Eocene; P5-P6/P7 (Lenticullina pseudomamillegarus) Zone; dated Early Eocene – Late Palaeocene and ?M18 (Bolivina afra) Zone; dated Maastrichtian – Late Campanian. The palaeoclimatic investigation from the recovered palynomorph and foraminifera assemblages revealed dominantly wet climatic environment which ranges from brackish to deep marine environments subjected to trangressive – regressive alternating environment covering Inner Neritic to Upper Bathyal settings.