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Crustal Structure of the Onshore Cenozoic Niger Delta Basin, Interpretations From High-Resolution Gravity and Magnetic Data


The nature of the crustal structure beneath the Cenozoic Niger Delta Basin has remained controversial and a challenging problem for regional basin evaluation. The high-resolution potential field data were evaluated using 2D forward modeling techniques with the aim of developing a better understanding of the nature of the crustal structure and the location of the continent ocean boundary (COB) within the Niger Delta. The 2D models were constructed using Bouguer gravity anomaly and magnetic data, constrained by seismic data and outcrop samples from part of the study area. The results obtained from the models show that the crustal thickness varies from 12 km at Okigwe area (NE) to about 24 km beneath Patani area at the centre of the delta to 12 km at Pennington area (SW) near the coastline of the delta. The depth to Moho estimated ranges from about 24 km at Okigwe area to more than 30 km at Patani area and to about 25 km at Pennington area. The Okigwe and/or Pennington area could mark the start of hyper-extended/transitional crust that lies beneath the Niger Delta. Thus, it is hereby suggested that the onshore Niger Delta Basin generally is underlain by thin continental or transitional crust and not oceanic crust as previous argued and the COB is observed at the offshore segment of the delta. This implies that the onshore-offshore portion of the Niger Delta is underlain by the continent ocean transition (COT) structure. This crustal structure suggests post-rift stage characteristics similar to the pure shear model mechanism for the evolution passive continental margins.