INTERPRETATION OF TOTAL MAGNETIC INTENSITY FIELD OVER BIDA BASIN

ABSTRACTThe Upper Cretaceous Bida Basin of central Nigeria is sandwiched between the Precambrian schist belts of the Northern Nigerian Massif and the West African Craton. It extends from Kontangora on its north western margin to Dekina in the southeastern margin where it merges with the Benue Trough. It lies between Longitude 40 and 70 and Latitude 70 and 110. Bida basin has an estimated length of 400km and maximum width of 160km which tapers to less than 60km at Dekina.    18 number of 1:100,000 aeromagnetic sheet maps were digitized in a gridded pattern at an interval of 1.1km and were processed, analyzed and interpreted both qualitatively and quantitatively in order to understand the geological configuration and structural trend of the basin. Different total magnetic intensity derivatives were calculated and interpreted to identify major structural trend in the Basin. 1st degree Polynomial fitting method was used separate the regional and residual field, which was later transformed using Fast Fourier Transform (FFT). Both manual and automatic depth estimation methods were used to estimate the depth to basement within the basin. 2D modeling of the residual field was done using GMSYS software package in four profiles.About five regional lineaments were identified across the basin likely to be Romanche Paleofracture zone earlier identified.  Two major E-W trending discontinuities exist in the southern part of the basin. The result from this study also showed that Bida basin is generally shallow (1-1.5km) but from the depth to basement analyses some deep pockets (2.5km -3.75km) were observed at Mokwa, Akerre, Kudu, Kotonkarfi, Auna and Bida areas. It is suggested that either drilling to the basement or seismic refraction be carried out in the above named areas to ascertain the source of deep magnetic sources, carry out stratigraphic study and explore for hydrocarbon source and reservoir rocks in this area since it satisfies thermal condition for its production.