Abstract:
A study of the biostratigraphy of Gbokoda-1 well in the western Niger delta was carried out
to unravel the age, paleoenvironment and palaeoecology of the strata penetrated by the well.
Standard micropaleontological techniques were used. Sedimentological study shows that the
analysed section belongs to the transitional, paralic Agbada Formation. The foraminiferal
assemblage consists of thirty-two foraminiferal species, comprising three planktonics,
Globigerinoides quadrilobatus, Globigerinoides sacculiferus and Globigerinodes spp and
twenty-nine benthics among which are Hanzawai strattonii, Heterolepa floridana,
Heterolepa inornata, Quinqueloculina lamarckiana, Amphistegina lessonii,
Quinqueloculina microcostata, and Cribroelphidium decipens. A total of fifty eight (58)
palynomorph species were also recorded among which are Zonocostites ramonae,
Monoporites annulatus, Sapotaceapollenites sp, Retitricolporite irregularis,
Retibrevitricolporites protundens, Botryococcus braunii and Laevigatosporites spp. Two
major benthic informal foraminiferal zones were recognized. They are the Hanzawaia
Strattonii / Amphistegina lessonii zone (1216–1838m) and the Amphistegina Lessonii /
Cribroelphidium Decipens Zone (1838-2057m). The studied interval of the well falls within
the broad pan tropical Echitricolporites/ Spinosus zone and dated middle Miocene to late
Miocene. Four paleobathymetric environments of deposition were deduced, namely: coastal
deltaic, inner neritic, inner neritic-middle neritic and middle neritic. From the percentage
composition of Monoporites annulatus and Zonocostites ramonae, the sequences were
deposited under alternation of wet and dry climatic conditions
