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As part of a major project to procure miscellaneous geophysical coverage of the entire country, the Geological Survey of Nigeria has acquired aeromagnetic data, presented as contour maps at various scales, over the nation's 7 sedimentary basins. The coverage over the Nigerian continental margin, acquired at 2,500 ft above sea level, was flown at 4-km flight-line spacing in a north-northeasterly direction and at 20-km tie-line spacing in a west-northwesterly direction. Another tie line was flown along the coastline.
Twenty 1:250,000, one-degree square, total-intensity aeromagnetic contour maps covering the marginal basins down to the shelf break were assembled into a single aeromagnetic map of the Gulf of Guinea cul-de-sac. The map area lies within lat. 3°-8°N, and long. 2°-9°E. It covers the Nigerian portion of the Dahomey embayment, the Anambra and Niger Delta basins, and the southern portion of the Benue rift. The map covers the location of the postulated Late Cretaceous triple junction involving the Benue Trough aulacogen, the northward-propagating South Atlantic, and the transform-dominated Equatorial Atlantic. In addition to the region seaward of the continental shelf, the map covers the Niger Delta basin, the basement of which is also inferred to consist mainly of ocean c crust prograded by the thick sediments of the Tertiary Niger delta. This area is also the location of the Late Cretaceous coalescence of the North Atlantic and South Atlantic spreading systems hitherto separate from one another.
This new aeromagnetic map fills an important data gap (due to proprietary restrictions and acquisition difficulties) in previous studies of this oil-prolific and geologically unique province. The map would be useful in future structural and tectonic studies of the Gulf of Guinea cul-de-sac.
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