Subsurface Structural Mapping over Koton Karifi and Adjoining Areas, Southern Bida Basin, Nigeria, using High-Resolution Aeromagnetic Data

E.B Ikumbur,V.E Ogah,M Akiishi

doi:10.36263/nijest.2019.02.0151

Abstract

In this current work, we aim to delineate the subsurface structural trends, determine the depth to basement surface, and provide an illustrative 3D model for its subsurface structure. Four digitized aeromagnetic maps were acquired from the Nigerian Geological Survey Agency, Abuja. The total field aeromagnetic anomalies over Koton Karifi and adjoining areas have been evaluated. In order to map the subsurface structures and estimate the depth to basement surface the spectral analysis method was applied. To achieve such goals, a detailed analysis of the aeromagnetic data for the study area was performed. 2D interpretation was carried out for the aeromagnetic data. The processes used include contouring of the Total Magnetic Intensity (TMI) data, separation of regional and residual anomalies, structural detection methods such as analytic signal, vertical derivatives, and magnetic lineament mapping were used to map the contacts and faults within the study area. The first vertical derivative and the magnetic lineament maps show major geologic lineaments trending in East-West with minor ones trending Northeast-Southwest. In the south-eastern part of the study area, there is a dome-shaped linear feature. The result obtained using the spectral analysis method reveals two source depth models. The depths to deeper magnetic sources range from 2.81 km to 3.24 km with an average depth of 2.90 km. The deeper magnetic source bodies are identified with the magnetic basement. The shallower magnetic sources which range from 0.45 km to 1.81 km with an average depth of 1.13 km could be attributed to near surface magnetic sources which are magnetic rocks that intruded into the sedimentary formations or magnetised bodies within the sedimentary cover. Based on the sedimentary thickness range of 0.45 to 3.24 km, there is an indication that the possibility of hydrocarbon generation in the study area is feasible.

Highlights

Magnetic lineaments over sedimentary basins are zones of gradient interruptions or zones marked by sharp changes of the orientation of anomalies
The qualitative interpretation was done by visual inspection of the total magnetic intensity, residual magnetic anomaly, analytic signal, first vertical derivative and magnetic lineament maps
Spectral analysis method has been applied to a set of high-resolution aeromagnetic data over KotonKarifi and Adjoining Areas

Summary

Introduction

Magnetic lineaments over sedimentary basins are zones of gradient interruptions or zones marked by sharp changes of the orientation of anomalies. These anomalies may be as a result of the faults affecting the underlying basement alone or both the basement and the sedimentary formations. We used the term ‘subsurface structure’ as defined by Ross et al, 2017, which is described as structural fabrics within the crystalline basement. Some of these are shear zones that have maintained their coherence during ductile deformation and some are faults or fault zones where coherence has been

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