A Neogene calcareous nannofossil biozonation scheme for the deep offshore Niger Delta

• Nannofossil distribution in the Early Miocene to Early Pliocene sequences of the offshore Niger Delta was investigated.
• A refined nannofossil zonation scheme has been erected for the offshore Niger Delta sequences studied.
• Several new ‘local’ nannofossil bioevents have been employed for zonal boundaries.

A detailed calcareous nannofossil analysis was carried out on the deep-water offshore Niger Delta strata penetrated by eight wells in order to erect a basin-wide Neogene biozonation scheme for the region. Four of the wells penetrated Miocene to Early Pliocene strata while the others drilled through Miocene sediments. The recorded rich and diversified nannofossil suites enabled the subdivision of the Neogene sequences into 13 zones [NN1 (CN1a) – Early Miocene to NN13 (CN10c) – Early Pliocene] and 15 subzones. Five (NN1, NN2, NN4, NN5 and NN11) zones are divided into subzones based on First and Last occurrences plus relative abundance of marker species. Dearth of nannofossils in the Middle Miocene NN5–NN8 zones precludes a refined zonation construction for the interval. Several new criteria are suggested for delineating new and previously erected zones. The resulting refined scheme offers an improved stratigraphic framework for correlation of thin reservoir units within and across Niger Delta fields.

Figure optionsDownload as PowerPoint slide