UPWARD CONTINUATION AND SPECTRAL ANALYSIS OF AEROMAGNETIC SIGNATURES OVER KALTUNGO AREA AND SURROUNDING CRETACEOUS SEDIMENTS, NORTHEASTERN NIGERIA

Abstract

The methods of Upward Continuation and Statistical Spectral Depth Analysis were applied on Aeromagnetic data over Kaltungo Area in the Upper Benue Trough, Nigeria and the results are presented in this study. The area is bounded by Latitude 9 'N to 10 'N and Longitude 11 'E to 12 'E with an area cover of about 12,100 km2. The Oasis Montaj software was used to isolate the residual field components from the total magnetic field and also to analyse the field at different upward continuation levels. A Slope Plot Program extract from MATLAB was used in determining the spectral depths to recorded magnetic sources in the subsurface while Surfer 8 was used to contour the resultant maps. The TMI/residual magnetic anomalies were found have a dominant SW-NE trend with magnetic high concentrating and stretching along a prominent SW-NE trending- Kaltungo fracture zone flanked on either side by moderately low-low magnetic anomalies. The depth to the shallow magnetic layer ranges from 0.60 to about 1.00 km while that of the deeper source ranges from 2.25 to 3.25 km. The first magnetic layer is attributed to magmatic intrusives which occurred at shallower depths both in the basement inlier and the sedimentary cover. The second magnetic layer is believed to originate from the basement. Since the depth to the basement is an alternative measure of the thickness of the sediments overlying it, it shows that the sedimentary cover in the area is generally thin. The area is unlikely to favour economic concentration of oil and gas due to its limited thickness and size of sediments and secondly due to the Tertiary-Quaternary magmatism in the basin but, may be worthwhile for prospecting some magnetic ore minerals. However, more data are needed for interpretation in order to actually unravel the economic potential of this area.