Depth to Basement determination using Source Parameter Imaging (SPI) of Aeromagnetic Data: An application to upper Benue Trough and Borno Basin, Northeast, Nigeria

Abstract

Source Parameter Imaging (SPI) of aeromagnetic data covering latitude 9.50 – 12.00 and longitude 9.50 – 12.00, which corresponds to upper Benue trough and southern Borno basin, northeast, Nigeria, was carried out for the purpose of investigating the sedimentary thickness beneath the subsurface. The study area is covered by 25 aeromagnetic maps. The aeromagnetic maps were digitized on a 3 km by 3 km grid and later compiled to produce a combined aeromagnetic data file of the study area. The 3 km spacing interval imposed a Nyquist frequency of 0.167 km-1 while the data file comprised 7921 data points. The Polynomial Fitting method was applied in the regional–residual separation. The depth to magnetic source was determined through several mathematical processing from various grids. The pre-processed grids from the residual grid as input grid are dx, dy and dz. These output grids were later served as input grids for SPI processing. First order derivative was adhered to, as the method is much more sensitive to noise at higher order of derivative. The result of the Source Parameter Imaging (SPI) has its highest sedimentary thickness of about 5.0 km around Gombe, AkoGombe, Bulkachuwa and Damaturu areas. The shallow sedimentary thickness could also be found in basement complex around Bauchi, Kaltungo inlier and volcanic areas at the eastern part of the study area. Detailed seismic survey and soil sample tests should be carried out around Gombe, AkoGombe, Damaturu and Bulkachuwa, these areas were suggested as having the highest sedimentary thickness of about 5.0 km, as this may determine the presence of hydrocarbon.