| Summary, etc |
Aeromagnetic and 2D Electrical Resistivity Tomography (ERT) data have been processed,<br/>integrated and interpreted for the purpose of mapping linear geologic structures at Mountain Top<br/>University’s permanent site in Makogi-Oba, Ibafo area of Ogun State which is currently being<br/>considered for development. The study was aimed at mapping linear geologic structures whose<br/>occurrences are to be given proper consideration in order to optimise land usage in the physical<br/>planning of the study area for development.<br/>The total magnetic field intensity (TMI) data were reduced to the magnetic equator to remove<br/>asymmetries associated with low magnetic latitude anomalies and was subsequently separated into<br/>its regional and residual field constituents. The residual field was enhanced using various<br/>techniques which included the Total Horizontal Derivative (THD), Standard Euler Deconvoluion<br/>and Tilt Derivative (TDR). Four 1110 m long 2D ERT profiles, probing a depth of about 220 m,<br/>were also acquired in the study area using the dipole-dipole array. The data were inverted using<br/>the “EarthImagerTM” software.<br/>The TMI map was observed to be dominated by elongated to linear magnetic anomalies trending<br/>mostly in the approximate N – S direction. Though having a low magnetic relief of about 2.6 nT,<br/>the study area reflected four magnetic field intensity zones which were characteristically distinct<br/>with magnetic intensity decreasing from West to East. The pattern of the decreasing magnetic<br/>intensities eastwards seemed to be suggestive of a step-faulting phenomenon with depth to the<br/>faulted blocks decreasing eastwards. The residual field map comprised of both elongated and<br/>spherical magnetic anomalies, some with relatively high magnetic intensities while others had<br/>relative low magnetic intensities. An intersection of magnetic lows in the eastern part of the study<br/>area was identified and interpreted to suggest that the study area is a shear zone. The lineaments<br/>delineated by the THD comprised of long, intermediate and short lineaments. From the THD map,<br/>the western and southern parts consist mostly of long and intermediate lineaments while the<br/>northeastern part was found to be dominated by short lineaments. The Euler Deconvolution mostly<br/>resolved long lineaments and their appendages but resolved less of isolated short lineaments. The<br/>integrated result of the THD and Euler deconvolution derived lineaments appreared to agree in a<br/>good part of the study area while in some parts it can be best described as complementary. From <br/>xiv<br/>the Euler Deconvolution solutions, depth estimates to the linear geologic structures rarely<br/>exceeded 200 m except in the central southern and central northern parts. Tilt derivative solutions<br/>presented depths to some delineated semi-regional to regional scaled structures as ranging between<br/>102.94 m and 286.76 m. The 2D ERT inverted section imaged three to four geoelectric layers<br/>which were interpreted as interclation of sand and clay. The immediate topsoil was found to be<br/>clayey and its thickness approached 8 m in some regions. Some structure suspected to be faults,<br/>coincident with the delineated magnetic lineaments, were imaged on the 2D ERT sections.<br/>The study area was found to be a shear zone having lots of linear geologic structures within it. The<br/>northwestern part of the study area appeared to be the least affected by the presence of linear<br/>geologic structures and may require less stabilisation for construction. The immediate topsoil being<br/>clayey, geotechnical competence tests may be required for the subgrade soil. To optimise the<br/>groundwater resources in the area, the linear geologic structures should be intersected at the<br/>northern region where they dip towards. |
