Aeromagnetic anomalies and tectonic trends in and around the Benue Trough, Nigeria

Four major fracture zones cutting the Atlantic sea floor off the west coast of Africa—St Paul's, Romanche, Chain and Charcot— have been delineated offshore using bathymetrie, seismic, gravity and magnetic data, respectively1. But the extrapolation of these fractures onto the African Continent is uncertain. Here we analyse recently compiled aeromagnetic data2 for the Benue Trough and adjacent areas of Nigeria, and demonstrate the existence of narrow magnetic lineaments parallel to the margins of the Benue Trough, which can be matched with the oceanic fractures. Alkaline ring complexes which predate the opening of the Atlantic Ocean are concentrated along these lineaments, suggesting that they represent pre-existing zones of weakness in the African crust which may have influenced the rifting of the continental margins and the early development of Atlantic fracture zones.