GEOLOGIC ANALYSIS AND INTERPRETATION OF AEROMAGNETIC DATA: AN EXAMPLE FROM THE ANAMBRA BASIN, SOUTH-EASTERN NIGERIA

Abstract

 This study focuses on geologic analysis and interpretation of an area bounded by Latitudes 50 56′ 30′′ N and 60 02′ 30′′ N and longitudes 70 19′ 59′′ E and 70 28′ 00′′ E in the South-eastern part of Nigeria, using airborne magnetic data. The objective was to investigate the lithologic and structural framework and hence predict the priority targets for exploration of geo-resources in the area. The method adopted involves analysis of spatial derivatives of the Total Magnetic Intensity (TMI) and the Bouguer Anomaly data combined with geology and topographic data. To that effect, data analysis involving comparative analysis of computer screen and hard-copy images and generation of maps for first vertical derivative, reduction-to-pole, analytical signal, SPI Depth to magnetic sources, Bouguer anomaly and topography for quantitative and qualitative interpretation was carried out. Qualitative interpretations through structural synthesis and lithological identification reveal regional faults with structures trending in various directions, and a high density trend, suggesting very thick piles of overburden sediments. Quantitative interpretations based on geologic cross-section on all relevant data indicate presence of dense sediments as well as variations in basin thickness and elevation. Lithologic characterization indicates that the work area cuts across formations with coal beds. Thus, the major target of viable geo-resources in this area is coal. It is recommended that ground geophysics be carried out in order to fully unravel the position, spread and geometry of coal seams as well as other suspected metallic minerals within the study area.