Determination of Depth to Magnetic Basement over Biu Plateau and Yola Sub-Basin, Northeastern Nigeria, using Source Parameter Imaging (SPI) and Euler Deconvolution Techniques

Abstract

Quantitative analysis of aeromagnetic data covering total area of 48,000 km2 on latitude 11.000 N to 13.000 N and Longitude 9.000 E to 11.000E, which corresponds to Basement Complex part of upper Benue trough northeastern, Nigeria was carried out with the aim of estimating the sedimentary thickness using Source parameter imaging and Euler deconvolution. The study area is covered by sixteen (16) aeromagnetic data sheet. Aeromagnetic data were analysed using the Oasis Montaj 8.3 software. The total magnetic map was reduced to magnetic equator with geomagnetic inclination of -4.3° and geomagnetic declination of -1.0o so as to get the actual position of the anomalies. The pre-processed grids dx, dy and dz from the reduced to magnetic equator map were used as input grids to calculate the source parameter imaging and Euler deconvolution. The results from the total magnetic intensity (TMI) and TMI - RTE shows that magnetic intensity values range from -94.1 nT to 235.5 nT and -80.261 nT to 234.153 nT respectively. The results indicate a dominant NE-SW, NW – SE and E – W orientation of faults and were also identified mostly at the edges of sediments-basement contacts. The result from SPI ranges from 0.110 km (shallow magnetic bodies) is observed at the northeast part of the study area which is made of crystalline rocks to 3.243 km (deep lying magnetic bodies) is observed at the Northwest, Southeast and Southwest part of the study area. The depths of the magnetic source bodies estimated from Euler deconvolution for the structural index SI = 1 ranges from 0.094 km (out cropping magnetic bodies) to 3.32 km (deep lying magnetic bodies). The shallower magnetic anomalies are as a result of basement rocks which intruded into the sedimentary rocks while the deeper magnetic anomalies are associated with magnetic basement surface and intra basement discontinuities like faults and fractures. The maximum sedimentary thickness of about 3.24 km and 3.32 km from SPI and Euler deconvolution respectively might be sufficient for hydrocarbon maturation in the area.