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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 3. (March)

First Page: 333

Last Page: 333

Title: Environments and Sediments of the Late Quaternary Niger Delta, West Africa: ABSTRACT

Author(s): J. R. L. Allen

Article Type: Meeting abstract


Sediments of the Late Quaternary Niger delta comprise the youngest layer of a thick sedimentary sequence, which has accumulated in the Nigerian Coastal Plain geosyncline since Cretaceous time. Many of the geosynclinal sediments can be assigned a shallow marine or deltaic origin, and the Late Quaternary delta is of interest as a possible model for the interpretation of earlier events.

The Late Quaternary delta is large in size and arcuate in form, lying in the tropics on the edge of a major ocean. The forces at work at sea have strongly influenced delta shape and growth. Sedimentation is taking place within a complex of environments: river floodplain, brackish mangrove swamp, beach and shoreface, river mouth bar, delta-front platform, prodelta slope, and open continental shelf. A further important environment in the offshore portion of the delta is non-depositional in character, and corresponds in area to outcrops on the sea bed of transgressive sands dating from the last eustatic rise of the sea. Bordering the delta proper are further environmental complexes: barrier islands and lagoons on the west, and estuaries with mangrove swamps on the east.

The deltaic sediments range from very coarse sands to silty clays. They become finer grained from the river floodplain, where sands predominate, to the open shelf, where silty clays are mainly found, and from the axis of symmetry of the delta to the delta flanks. Only in the broadest sense is there correspondence between environment and lithofacies boundaries. The nature of lithofacies deposited in a given environment is a function of factors operating within the environment and of the materials supplied to the environment from without. Sediment is dispersed in both down-delta and across-delta directions. For a depositional environment to be ascertained from lithofacies, in many cases a knowledge of position within the delta is also required.

Like many other Late Quaternary deltas, the Niger delta shows a two-fold stratigraphic division. The unit first formed is a thin but widespread sheet of sand, moulded locally into barrier complexes now drowned that accumulated as a strand-plain deposit during the last eustatic rise of the sea. The later unit, built out over but not yet completely covering the transgressive sands, comprises regressive delta deposits formed in the environments listed.

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Copyright 1997 American Association of Petroleum Geologists