Qualitative Evaluation of Geophysical Aeromagnetic Data For River Anticline Around The River Niger Area In Koton-Karfi, Southern Bida Basin, Nigeria

In this paper a qualitative evaluation of aeromagnetic data maps has been used to preliminarily support the formation of river anticlines beneath major rivers due to isostatic rebound as a result of deep river incision of surface and sub-surface overlying rocks. The regional gradients of digital high resolution aeromagnetic data were removed by polynomial fitting. This involved fitting a plane surface to the reduction to pole map of the aeromagnetic data by using multi-regression least square analysis of the Oasis Montaj 6.4 program. The regional field values from the plane surface are subtracted from the observed data to obtain the residual anomaly values. Power spectrum plots of aeromagnetic data of the study area produced a basement depth contour map. The basement depths of the south-western part of the study area revealed basement uplift with a depth range of 1.8 to 2.5km which lies beneath the Niger River area, SW of the study area, and depicts a river anticline.