Interpretation of Aeromagnetic Data over the Nigerian Sector of the Mamfe Basin

Abstract

Four Aeromagnetic data over a part of the Nigerian Sector of the Mamfa Basin have been analyzed using qualitative approach and spectral analysis. The aeromagnetic maps, its analytic signal amplitude and geological modelling sketch helped in identifying the nature and depth of the magnetic sources in the study region. The qualitative interpretation reveals that the study area is characterized by magnetic lineament trend in NE-SW direction and subordinate E-W direction. The results obtained are in line with the trend of the Benue Trough. The aeromagnetic maps reveal that the sedimentary thickness increases towards the northern parts of the study area. The results also reveal that the total magnetic field intensity range from 7800 to 8290 nanotesla (nT) in the study area. The residual anomaly map reveals that the maximum anomaly value is 160nT which is found around Bansara and Ugep environs while the minimum magnetic value is -140nT towards the Abakiliki and Ikom areas. Results from spectral analysis indicated two magnetic source depths, which account for deeper and shallower sources. The deeper magnetic sources vary from 2.76 km near Abakiliki to 5.37 km near Bansara, whereas the shallow magnetic sources vary from 0.58 km near Ikom to 1.76 km near Ugep. The depth to basement map reveals that the sediment thickness increases towards the northern parts of the study area. The depths to basement are deeper in the northern and central parts trending northwest-southeast direction and shallower in the eastern and southern parts of the study area. The result also shows a linear depression with sedimentary accumulation trending northwest-southeast. The temperatures at depth for each anomaly block were estimated to range between 48.46 and 225.69°C with an average of 117.04°C. Based on the computed sedimentary thickness (2.76-5.37km) and temperature at depth (62-220°C), the possibility of hydrocarbon generation in the northern and central parts of the study area is realistic