Stratigraphy and sedimentology of the Niger Delta
During the Cenozoic, until the Middle Miocene, the Niger Delta grew through pulses of sedimentation over an oceanward-dipping continental basement into the Gulf of Guinea; thereafter progradation took place over a landward-dipping oceanic basement. A 12,000 m thick succession of overall regressive, offlapping sediments resulted that is composed of three diachronous siliciclastic units: the deep-marine pro-delta Akata Group, the shallow-marine delta-front Agbada Group and the continental, delta-top Benin Group.
Regionally, sediment dispersal was controlled by marine transgressive/regressive cycles related to eustatic sea-level changes with varying duration. Differential subsidence locally influenced sediment accumulation. Collectively, these controls resulted in eleven chronostratigraphically confined delta-wide mega-sequences with considerable internal lithological variation.
The various sea-level cycles were in or out of phase with each other and with local subsidence, and interfered with each other and thus influenced the depositional processes. At the high inflection points of the long-term eustatic sea-level curve, floodings took place that resulted in delta-wide shale markers. At the low inflection points, erosional channels were formed that are often associated, downdip, with turbidites in low-stand sediments (LSTs). The megasequences contain regional transgressive claystone units (TST) followed by a range of heterogeneous fine-to-coarse progradational or aggradational siliciclastic (para)sequence sets formed during sea-level high-stand (HST).
An updated biostratigraphic scheme for the Niger Delta is presented. It also updates a sedimentation model that takes into consideration local and delta-wide effects of sea-level cyclicity and delta tectonics. Megasequences were formed over time intervals of ~5 Ma within individual accurate megastructures that laterally linked into depobelts. The megasequences form the time-stratigraphic frame of the delta and are the backbone for the new delta-wide lithostratigraphy proposed here. Such a new lithostratigraphy is badly needed, in particular because of the vigorous new activity in the offshore part of the Niger Delta (not covered in this contribution). There, as well as in the onshore part of the delta, the traditional lithostratigraphic subdivision of the Cenozoic Niger Delta section into three formations is insufficient for optimum stratigraphic application; moreover, the various informal subdivisions that have been proposed over time are inconsistent.
Berggren, W. A. & Hollister, C. D., 1974. Paleogeography, paleobiogeography and the history of the circulation in the Atlantic Ocean. [In:] W. W. Hay (Ed.): Studies in paleo-oceanography. SEPM Special Publication 20, 126-185.
Brink, G. J., Keenan, J. H. G. & Brown Jr., L. F., 1993. Deposition of fourth-order, post-rift sequences and sequence sets, Lower Cretaceous (Lower Valanginian to Lower Aptian, Pletmos Basin, Southern offshore, South Africa. [In:] P. Weimer & H. W. Posamentier (Eds): Siliciclastic sequence stratigraphy. AAPG Memoir 58, 492 pp.
Burke, K., 1972. Longshore drift, submarine canyons and submarine fans in Development of Niger Delta. American Association of Petroleum Geologists Bulletin 56, 1975-1983.
Cahen, L. N. J. Snelling, Delhal, T. & Vail, J. R., 1984. The geochronology and evolution of Africa. Oxford Science, London.
Cloeting, S., McQueen, H. & Lambeck, K., 1985. On a tectonic mechanism for regional sea-level variations. Earth and Planetary Science Letters 75, 157-166.
Curtis, D. M., 1970. Miocene deltaic sedimentation, Louisiana Gulf Coast. [In:] J. P. Morgan (Ed.): Deltaic sedimentation - modern and ancient. SEPM Special Publication 15, 293-308.
Durand, J., 1995. High resolution sequence stratigraphy (genetic stratigraphy) in reservoir sedimentology: examples from the Niger Delta. Nigerian Association of Petroleum Explorationists Bulletin 10, 65-73.
Ejedawe, J. E., 1981. Patterns of incidence of oil reserves in Niger Delta Basin. American Associatioin of Petroleum Geologists Bulletin 65, 1574-1585.
Ejedawe, J. E., Coker, S. J. L., Lambeth-Aikhionabare, D. O., Alofe, K. B. & Adoh, E. O., 1984. Evolution of oil-generative window and oil and gas occurrence in Tertiary Niger Delta Basin. American Association of Petroleum Geologists Bulletin 68, 1744-1751.
Evamy, D. D. J., Haremboure, P., Kamerling, W. A., Knaap, F. Molloy, A. & Rowlands, M. H., 1978. Hydrocarbon habitat of the Tertiary Niger Delta. American Association of Petroleum Geologists Bulletin 62, 1-39.
Galloway, W. E., 1989. Genetic stratigraphic sequences in basin analysis 1: Architecture and genesis of flooding-surface bounded depositional units. American Association of Petroleum Geologists Bulletin 73, 125-142.
Harland, W. B., Armstrong, R. L., Cox, A. V., Craig, L. E., Smith, A. G. & Smith, D. G., 1990. A geological time scale 1989. Cambridge University Press, Cambridge, 263 pp.
Haq, B. U., Hardenbol, J. & Vail, P. R., 1988. Mesozoic and Cenozoic chronostratigraphy and cycles of sea level changes. [In:] C. K. Wilgus, B. S. Hastings, H. Posamentier, J. van Wagoner, C. A. Ross & C. G. S. C. Kendall (Eds): Sea-level changes - an integrated approach. SEPM Special Publication 42, 71-108.
Jubril, M. A. & Amajor, L. C., 1991. The Afam Clay Member: a Lower Miocene incised channel in the south-eastern Niger Delta. Marine and Petroleum Geology 8, 163-173.
Knox, G. J. & Omatsola, M. E., 1987. Development of the Cenozoic Niger Delta in terms of the escalator regression model. [In:] Proceedings of the KNGMG Symposium ‘Coastal Lowlands - Geology and Geotechnology’. Kluwer Academic Publishers, 181-202.
Ladipo, K. O. 1992. Sequence stratigraphic analysis: an example of applications to prospect appraisal in the Northern (western) Niger Delta, Nigeria. Nigerian Association of Petroleum Explorationists Bulletin 7, 153-158.
Magbagbeoloa, O. & Willis, B. J., 2007. Sequence stratigraphy and syndepositional deformation of the Agbada Formation, Robertkiri field, Niger Delta, Nigeria. American Association of Petroleum Geologists Bulletin 91, 945-958.
Miall, A. D., 1997. The geology of stratigraphic sequences. Springer, Berlin, 433 pp.
Mitchum Jr., R. M. & Van Wagoner, J. C., 1990. High-frequency sequences and eustatic cycles in the Gulf of Mexico Basin. [In:] J. M. Armentrout & B. F. Perkings (Eds): Sequence stratigraphy as an exploration tool-concepts and practices in the Gulf Coast. Gulf Coast Section, SEPM, Program and Abstracts Eleventh Annual Research Conference, Houston, p. 257-267.
Mitchum Jr., R. M. & Van Wagoner, J. C., 1991. High frequency sequences and their stacking patterns: sequence-stratigraphic evidence of high-frequency eustatic cycles. Sedimentary Geology 70, 131-160.
North American Commission on Stratigraphic Nomen-clature, 1983. North American Stratigraphic Code. American Association of Petroleum Geologists Bulletin 67, 841-875.
Orife J. M. & Afbovbo, A. A., 1981. Stratigraphic and unconformity traps in the Niger delta - Abstract. American Association of Petroleum Geologists Bulletin, 251-265.
Owoyemi, A. O. & Willis, BJ., 2006. Depositional patterns across syndepositional normal faults, Niger delta, Nigeria. Journal of Sedimentary Research 76, 346-363.
Petters, S. W., 1982. Central West African Cretaceous-Tertiary benthic foraminifera and stratigraphy: Palaeontographia A 179, 1-104.
Petters, S. W., 1983. Gulf of Guinea planktonic foraminiferal biochronology and geological history of the South Atlantic. Journal of Foraminiferal Research 13, 32-59.
Petters, S. W., 1984. An ancient submarine canyon in the Oligocene-Miocene of the western Niger Delta. Sedimentology 31, 805-810.
Reijers, T. J. A., Petters, S. W. & Nwajide, C. S., 1997. The Niger Delta Basin. [In:] R. C. Selley (Ed.): African basins. Sedimentary Basins of the World (Elsevier, Amsterdam) 3, 145-168.
Short, K. C. & Stauble, A. J., 1967. Outline geology of the Niger Delta. American Association of Petroleum Geologists Bulletin 51, 761-779.
Sloss, L. L., 1963. Sequences in the cratonic interior of North America. Geological Society of America Bulletin 74, 93-113.
Sloss, L. L., Krumbein, W. C. & Dapples, E. C., 1949. Integrated facies analysis. [In:] C. R. Longwel (Ed.): Sedimentary facies in geologic history. Geological Society of America Memoir 39, 181-191.
Stacher, P., 1995. Present understanding of the Niger Delta hydrocarbon habitat. [In:] M. N. Oti & G. Postma (Eds): Geology of deltas. Balkema, Rotterdam, 257-268.
Vail, P. R., 1987. Seismic stratigraphy interpretation, using sequence stratigraphy. Part I: Seismic stratigraphic procedure. [In:] A. W. Balley (Ed.): Atlas of seismic stratigraphy 1. American Association of Petroleum Geologists Studies in Geology 27, 1-10.
Weber, K. J., 1971. Sedimentological aspects of oil fields in the Niger Delta. Geologie en Mijnbouw 50, 559-576.
Weber, K. J. & Daukoru, E., 1975. Petroleum geology of the Niger Delta. Proceedings of the Ninth World Petroleum Congress 2, 209-221.