2D ERT Research Articles

Assessment of rainfall-induced slope failures at Chakargoan, Port Blair, India, using 2D ERT and self-potential techniques

Assessment of rainfall-induced slope failures at Chakargoan, Port Blair, India, using 2D ERT and self-potential techniques

Integration of 2D and 3D electrical resistivity tomography and 2D gravity modeling to evaluate groundwater investigations in the Burka Uke catchment area, western Ethiopia

The increasing demand for water resources due to the expanding infrastructure and growing population of Uke town, West Ethiopia, necessitates a comprehensive understanding of groundwater potential within the Burka Uke catchment. The aims and objectives of this study are to identify a map of the aquifer by characterizing the subsurface earth, basement rock depth, resistivity and density of geological layers, their thicknesses, and structural features. The investigation integrates electrical resistivity tomography and gravity modeling to delineate potential groundwater zones and their structural controls. Electrical resistivity tomography profiles (1, 4, and 6) revealed low resistivity zones indicative of potential aquifers. The significant resistivity contrast (378 to 1412 Ω.m) suggests a high fracture density, potentially enhancing groundwater storage. The Bouguer gravity anomaly map, separated into regional and residual components, displayed values ranging from 51.79 to 41.59 mGal, highlighting density variations in the subsurface. As a result, analysis of the residual gravity anomaly map identifies north–south striking fault elements, indicating their influence on groundwater flow.The combined 2D and 3D ERT data also revealed a 2D gravity model of the aquifer from which the concentration extended throughout the study area. Data validation with previously drilled wells has confirmed the effectiveness of the geophysical methods used in identifying potential groundwater zones. This study provided critical information for the sustainable management of existing groundwater and demonstrated the effectiveness of integrating geophysical techniques to delineate and characterize aquifers in water-stressed areas.

The “Annunziata” Garden in Cammarata (Sicily): Results of integrated geophysical investigations and first archaeological survey

A multi-method geophysical investigation was carried out in the context of a recovery project for the “Annunziata” Garden located in the town of Cammarata (Sicily), near to the homonymous church (Chiesa dell'Annunziata). In this area, according to the scarce historical sources, there was a Benedictine convent, probably demolished in the 18th century, but the area was probably inhabited even in earlier periods. Preliminarily, a series of 2D electrical resistivity tomographies (2D-ERT) were carried out approximately parallel to each other, some of which highlighted resistivity anomalies that could be attributed to buried archaeological structures. Consequently, in a smaller area where these anomalies were evident, a 3D electrical resistivity tomography (3D-ERT) and Ground Penetrating Radar (GPR) parallel profiles were carried out aimed at a detailed 3D reconstruction of the subsoil. Despite the unclear correspondence between the 3D-ERT inverse model and the GPR one, the 3D ERT confirmed the anomalies found with the previous 2D-ERT surveys, better defining its contours and geometries. The geophysical reconstructions served to indicate to the archaeologists the most promising areas for excavation tests that were carried out subsequently and confirmed the presence of archaeological structures, such as defensive walls whose origin and dating are still the subject of further archaeological studies.

Groundwater potential assessment in parts of Nnewi Industrial Zone: Implications for sustainable development and conservation

Integrated field geological and geophysical (Vertical Electrical Sounding VES and 2D Electrical Resistivity Tomography ERT) investigations were carried out in the Nnewi Industrial Zone, SE Nigeria to identify and characterize productive aquifer, aquifer hydraulic properties, and aquifer vulnerability. Data acquired from 17 VES points and across a profile line of about 800 m for the 2D ERT were processed, interpreted, and modeled. Results from the geologic mapping showed that the outcropping units are mainly the sandstone, shaly-sandstone, and less commonly shale of the Nanka and Ogwashi-Asaba Formations which are relatively permeable and offer poor protective cover to the underlying aquifer. Models from the resistivity data showed that the depth-to and thickness of the aquifer vary from 38.60 to 98.80 m and 30.10–177 m, respectively. Aquifer properties estimated from the geophysical data gave values ranging from 0.611127 m2/day to 246.6576 m2/day and 0.1609 m/day to 5.6325 m/day for transmissivity and hydraulic conductivity, respectively, and suggestive of low – moderate aquifer potential. Aquifer Protective Capacity APC distribution modeled from the longitudinal conductivity values, and the aquifer vulnerability modeled using the DRASTIC method indicate that the study area is characterized by poor – moderate APC and low – moderate – high aquifer vulnerability, respectively. Analysis shows that the modeled aquifer parameters, APC, and aquifer vulnerability have similar trend which tends to improve towards the southern and more specifically southeastern parts of the study area, suggesting that even though aquifer units were identified all through the study area, the southeastern parts are best suited for the development of groundwater exploitation schemes. Also, aquifer vulnerability model results recommend that proper and efficient waste disposal schemes are put in place to conserve groundwater quality from pollution from industrial waste since the aquifer in the area is relatively vulnerable.

Monitoring of simulated clandestine graves of victims using UAVs, GPR, electrical tomography and conductivity over 4-8 years post-burial to aid forensic search investigators in Colombia, South America

In Colombia there are estimated to be over 121,000 missing people and victims of forced disappearances. Forensic investigators therefore need assistance in determining optimal detection techniques for buried victims, to give victims’ families closure and for the wider community to see that justice is being served. Previous research has created 12 controlled simulated clandestine graves of typical Colombian murder victim scenarios at 0.5 m – 1.2 m depths in savannah and rainforest sites in Colombia. The 0–3 years of geophysical monitoring results of were published, with this paper reporting on 4–8 years monitoring of both UAV drone results and geophysical data. The UAV results from the year 8 survey, published for first time from Colombia, showed that the simulated graves could still be located using NDVI and NIR multi-spectral data, but not using optical or other multi-spectral data. The 0–3 years of geophysical data found the simulated clandestine graves could be detected with electrical resistivity and GPR methods, with the 4–8 year surveys evidencing that they could still be detected using bulk ground conductivity surveys, GPR horizontal time slice datasets and 2D ERT profiles. Research implications suggest initial use of UAV remote sensing technology to pinpoint likely search areas, before subsequent ground reconnaissance, geophysical surveys and their interpretation, before intrusive investigation methods are employed for detecting missing and disappeared persons in Colombia.

Assigning resistivity values to rock quality designation indices using integrated unmanned aerial vehicle and 2D electrical resistivity tomography in granitic rock

Rock quality designation (RQD) is a standard technique in mining and geotechnical investigation for quantifying the quality and degree of jointing of the rock mass. However, the need for expeditious and inexpensive geotechnical site characterization is the prime motivation for modifying RQD. This research work integrates 2D Electrical Resistivity Tomography (2D ERT) and Unmanned Aerial Vehicle (UAV) conducted at Site 1 and Site 2. The UAV survey was performed to calculate RQD on the rock surface using volumetric Joint Counts (Jv) at Sites 1 and 2. A 2D ERT survey was conducted to obtain the corresponding subsurface resistivity values. Using k-nearest neighbours (k-NN), resistivity values were assigned to various RQD indices such as very poor rocks (<350 Ωm), poor rock (350–1150 Ωm), fair rock (1150–1850 Ωm), good rock (1850–2500 Ωm) and >2500 Ωm excellent rock. Based on the established correlation of RQD and resistivity, the subsurface rock mass quality at Site 1 was predominantly good and excellent rock, while at Site 2, poor rock was significantly reported. This research concluded that rock mass characterization using RQD is more rapid and inexpensive than the direct or indirect calculation of RQD. The combined 2D ERT and UAV deployed in this research study provide an environmentally non-destructive approach for slope stability assessment.

Cross-street electrical resistivity imaging for environmental applications

Road collapse has always been an important safety hazard for urban traffic, causing a serious threat to the safety of passing vehicles and citizens. However, the complex urban surface environment with obstacles such as huge buildings, hardened roads, and river network limits the application of ERT in cities. Here we present an innovative cross-street electrical resistivity imaging method. This method abandons the mandatory electrode grid layout that conventional 3D ERT required. Only two survey lines are required to be laid along sides of the street parallelly, gathering the apparent resistivity data set by the combination of current supply and potential electrodes across the street and obtaining the 3D resistivity imaging under street. It is well suitable for detecting and monitoring of hardened road and enhances the feasibility and the adaptability of ERT in urban. A series of numerical models and comparisons among this method and conventional ERT had been done. The modeling results show that this cross-street method reaches the resolution of the conventional 5-lines ERT, and its resolution to objects cross road are better than the conventional ERT. This method can both satisfy the exploration needs with difficult surface conditions such as roads, and greatly reduce the exploration workload. It shows well application prospects, such as hidden geological problem monitoring while combining with time-lapse ERT instruments.

Groundwater Potential Assessment of Penang Island, Malaysia, Through Integration of Remote Sensing and GIS with Validation by 2D ERT

Groundwater Potential Assessment of Penang Island, Malaysia, Through Integration of Remote Sensing and GIS with Validation by 2D ERT

An expeditious approach for slope stability assessment using integrated 2D electrical resistivity tomography and unmanned aerial vehicle survey

A comprehensive slope stability assessment of two sites, namely Site 1 and Site 2, has been conducted. An integrated Unmanned Aerial Vehicle Survey (UAV) and 2D Electrical Resistivity Tomography (2D ERT) survey at both sites were carried out. The rock mass quality using Rock Quality Designation (RQD) system was quantified, and discontinuity orientations were obtained from the UAV point cloud. The obtained discontinuity orientations were utilized to identify possible geometric failures such as planar, flexure and wedge. The 2D ERT survey at both sites was deployed to discern subsurface lithology. Based on the UAV survey, Site 1 slope was prone to flexure toppling and wedge failure. While few intersections at Site 2 were favourable for Wedge formations. 2D ERT survey reported four geological layers as water-saturated zone or clay layer (200–300 Ωm), highly fractured rock (400–700 Ωm), fractured rock (800–2200 Ωm) and fresh rock (>2200 Ωm) at both study sites. Combining the information of both techniques, the rock mass at Site 1 is moderately fractured to fresh rock. However, the top portion of Site 1 is highly fractured as compared to the lower portion. The rock quality at Site 2 is moderate to highly fractured rock mass. The integrated approach applied in this research study was proven expeditious, inexpensive and rapid for comprehensive slope stability assessment.

Electrical Resistivity Survey on Two Waste Dumpsites at Nguru, Potiskum, Yobe State, Nigeria to Determine the Effect of Leachates on Ground Water Aquifer

The research intends to bring out the contribution of leachate on groundwater in two dumpsites in Nguru and Potiskum all in Yobe state, Nigeria. A total of seven (7) and eight (8) VES by Schlumberger electrode with the use of Wenner electrode configuration. The results were interpreted by the use of WinRESIST for VES and IPWIN2INV for ERT. The study pointed out that, the area in question is comprised of four layers of geoelectric such as the topsoil, clay, sand, sandy clay and sand. The range of the first resistivity layer was from 6.16 Ωm to 332 Ωm in the first geo-electric layer and its thickness range from 2.77 m to 37.7 m and a depth range of 2.77 m to 37.7 m. the range of the second resistivity layer was from 16.5 Ωm to 37.9 Ωm which has the range of its thickness from 4.1 m to 10.7 m. The range of the third resistivity layer was from 101.2 Ωm to 288.2 Ωm which has the range of its thickness from 38.9 m to 99.7 m, and the first aquifer in the area. The range of the first resistivity layer was from 100.7 Ωm to 214.3 Ωm which has the range of its thickness from 28.5 m to 94 m. The fifth layer which is the second aquifer and has resistivity from 254 Ωm to 350 Ωm with a very large thickness. The range of the first resistivity aquifer is from 101.2 Ωm to 288.2 Ωm and the range of the second resistivity aquifer is from 253.8 Ωm to 350.1 Ωm. The 2D ERT profiles unveiled areas with low resistant zones and later discussed as zones penetrated by contaminants originated from dumpsites whereas high resistant zones represent areas of low or non-conductive materials in the area. Data obtained from four dumpsites indicated that leachate of the waste dumpsites penetrated into aquifers and polluted the groundwater. The existence of contaminants in the water was noted by a decrease in the formation resistant values. It is seen, from the results of the survey (geophysical) that the water in the area is polluted and it accounts for the prevalence of any disease related to water that are common in the area

Study of multi-electrode excitation mode for 3D electrical resistance tomography

Multi-electrode excitation is an effective way to improve the performance of 3D electrical tomography (ET) system compared with single electrode excitation. This paper systematically discusses various sensing strategies for multi-electrode excitation with different combinations in radial and axial directions. A typical 3 × 8 3D ERT sensor is adopted to analyze the influence of different excitation modes on performance indexes, such as number of independent measurements, dynamic range of measurements, sensitivity distribution and correlation coefficient of image reconstruction. On the basis of radial rotation angle between the excitation electrodes mapped to the same plane and whether the excitation electrodes are located in the same axial layer, five typical electrode combination modes are designed under dual-electrode excitation and single-electrode measurement protocol. The results show that the variation trend of different indexes influenced by excitation mode is inconsistent. The entropy-based method is applied to comprehensively evaluate the different excitation modes with the selected multiple performance indexes. Among all above modes, the mode in which excitation electrodes are vertically aligned is better universal one. The experimental results show that the position characteristics of the preferable mode can obtain better image reconstruction quality in different distribution models. Furthermore, the better excitation mode will provide guidance for design of other multi-electrode excitation in 3D ET systems with different structures.

Application of Electrical Resistivity Method to Site Characterisation for Construction Purposes at Institute of Agriculture Research and Training Moor Plantation Ibadan

This research was carried out within Institute of Agriculture Research and Training Moor Plantation Ibadan, Southwestern Nigeria, with the aim to ascertain suitability of the proposed site for building construction and usage. The geophysical investigation involved three electrical resistivity techniques; Vertical Electrical Sounding (VES) using the Schlumberger configuration, 2D ERT and 2-D electrical imaging using Dipole-dipole electrode configuration. Two traverses were established E–W direction cutting across geologic strike with a distance of 80 m and of varying inter-traverse spacing. Eight (8) VES stations were occupied covering the entire study area for layer stratification and geoelectric parameters. The results were qualitatively and quantitatively interpreted and are presented as sounding curves and geoelectric sections. The 2-D imaging gave information on the subsurface characteristic in the area with generally low apparent resistivity indicating low competence material. The results obtained from the VES delineate three geoelectric units which comprise of the topsoil, weathered layer and fresh basement. The results from the VES were used to determine the second order parameters. The entire results correlate well with one another showing that all the techniques used were complemented. This study has further justified the need for geophysical site investigation as pre-condition before any construction to avoid problems of differential settlement. In determining of foundation material, topography elevation, clay content and the depth of weak zones should be put into consideration, since the depth of the weak zone is appreciably high.

Integrated geophysical and geochemical assessment of submarine groundwater discharge in coastal terrace of Tiruchendur, Southern India

Submarine groundwater discharge (SGD) study is essential for groundwater in coastal terrace at Tiruchendur. The famous Murugan Temple is located in the area and around 25,000 people who visit this temple use the SGD well water at NaaliKinaru (a small open well) as holy water and drink it. The rock and soil type are sandy clay, silt, beach sand, calcarenite, kankar, gneissic rock and charnockite in base rock. Megascopic identification method was used to identify the porous and permeable rocks such as calcarenite, sandstone and kankar to support to increase SGD flux. Grain size study was used to identify the paleo-coastal estuarine environment with sediment deposits in the terrace. The square array electrical resistivity method was used to study the subsurface geology and aquifer depth. The 2d ERT technique was used to identify the subsurface shallow perched aquifer of freshwater. The magnetotelluric survey method was used to scan the entire subsurface geological and tectonic uplift, coastal ridges, rock folded subsurface structural features of continental and oceanic tectonism. Darcy’s law was used to calculate the SGD flux rate in the above study area.

Utilizing NWCR optimized arrays for 2D ERT survey to identify subsurface structures at Penang Island, Malaysia

In this paper, the effectiveness of optimized and conventional resistivity arrays for resolving shallow geological features was investigated at Penang Island, Malaysia. The assessment was between the inversion results from Noise-Weighted Compare R (NWCR) optimized arrays, and commonly used conventional arrays (Dipole-Dipole (DD) and Wenner-Schlumberger (WS)). This is demonstrated using two field cases studies. The first case was conducted at an area characterized by fractures /cracks in the walls and ceiling of a heritage building in Georgetown city. The aim was to identify the weakness zone responsible for the observed fractures. The second case study was conducted in the main campus of Universiti Sains Malaysia (USM), to delineate the interface between the granitic bedrock and the unconsolidated sediments. In the first case, the results show a layer with a resistivity value of less than 2 Ohm-m between 2 m to 6 m depth. This layer could be the weak zone in the investigated area. The NWCR optimized arrays detected this zone better than the DD and WS. This finding correlates quite well with the shear wave velocity (Vs) model, with Vs less than 115 m/s in the same line and depth. For the second case study, the results were compared with the borehole log in the middle of the resistivity line. The ERT model obtained from the NWCR defines the granitic surface at around 32 m depth, which correlates well with the borehole log, while the model from the DD arrays underestimated depth. In summary, the NWCR optimized arrays give a more accurate image of the subsurface resistivity distribution, followed by the DD array. The WS array performed the least.

Integrating electrical resistivity tomography and ground‐penetrating radar methods to map archaeological walls near northern Ishtar gate, ancient Babylon city, Iraq

AbstractElectrical resistivity tomography (ERT) and ground‐penetrating radar (GPR) were collected on the eastern side of the northern Ishtar gate in ancient Babylon, Iraq, to locate the palace wall and other surrounding walls. Due to the presence of a low resistivity (highly conductive) top layer associated with brick rubble and other debris, the GPR reflection profiles show a high‐energy attenuation, but a series of processing and filtering steps produced coherent reflections of about 2 m depth. Profile analysis shows the geometry and layering of the walls and the surrounding matrix. With the ERT, the surface conductive zone produces various distortions in ERT inverse models, making identifying the features' lower boundaries difficult. Here, we suggest that instead of analysing these two data sets independently, the integration of both reveals not just the walls but their composition and defines material in the surrounding units. This integration shows how the interpretation of the shallow features on the 3D ERT maps is improved by comparison and interpretation in conjunction with the reflections visible on both reflection profiles and the 3D GPR amplitude slices. The orientation of these features and reflections emphasizes the existence of one series of buried walls at a depth of 90–150 cm. The thickness of these walls varies between 0.25 and 1 m. Another wall‐like feature is visible only on 3D ERT maps and not with the 3D GPR slices at 2 m depth, which indicates a thickness of 11 m. It is interpreted as the palace wall, which is consistent with earlier archaeological excavations. An analysis of the geometry and composition of both wall components, perhaps of different ages, and constructed for different reasons, indicates that some shallower walls may be the remains of rooms built as residences for soldiers, or they may belong to the other ruins of northern Ishtar gate.

The Sacred Waterscape of the Temple of Bastet at Ancient Bubastis, Nile Delta (Egypt)

Sacred water canals or lakes, which provided water for all kinds of purification rites and other activities, were very specific and important features of temples in ancient Egypt. In addition to the longer-known textual record, preliminary geoarchaeological surveys have recently provided evidence of a sacred canal at the Temple of Bastet at Bubastis. In order to further explore the location, shape, and course of this canal and to find evidence of the existence of a second waterway, also described by Herodotus, 34 drillings and five 2D geoelectrical measurements were carried out in 2019 and 2020 near the temple. The drillings and 2D ERT surveying revealed loamy to clayey deposits with a thickness of up to five meters, most likely deposited in a very low energy fluvial system (i.e., a canal), allowing the reconstruction of two separate sacred canals both north and south of the Temple of Bastet. In addition to the course of the canals, the width of about 30 m fits Herodotus’ description of the sacred waterways. The presence of numerous artefacts proved the anthropogenic use of the ancient canals, which were presumably connected to the Nile via a tributary or canal located west or northwest of Bubastis.

Hydraulic conductivity and geophysics (ERT) to assess the aquifer recharge capacity of an inland wetland in the Brazilian Savanna

The inland wetlands can perform the storage of water on the surface and the recharge of aquifers. Even a small wetland can work as a local point of water infiltration, influencing and sustaining the hydrodynamics in the hydrology landscape. These zones have complex mechanisms, as they integrate soil chemical and physical characteristics, and relate both surface and groundwater systems. The study area is an inland wetland located in the Ecological Station of Itirapina, São Paulo State (Brazil). The present work aims to unveil the relationship between hydrodynamics and pedological architecture through a detailed study that combines hydraulic conductivity tests in situ, geophysical method of electrical resistivity (Electrical Resistivity Tomography technique, ERT), and morphological soil descriptions aiming the validation of the ERT and hydraulic conductivity surveys. Two-dimensional (2D) and pseudo-three-dimensional (3D) ERT have been used to investigate the water flow in the subsurface, the pedological architecture that keeps the wetland hydroperiods, and the link between surface water and groundwater that can set a recharge capacity. The results showed areas with distinct surface patterns related to the density of vegetation cover and water infiltration. The lower infiltration areas are characterized by the presence of a perched water table in grassy areas while higher infiltration is associated with exposed topsoil. ERT 2D and pseudo-3D identified these areas as zones with a connection between soil-water and groundwater systems. Hydrodynamics in the flat plateau is associated with the geochemical evolution of soil cover due to the structural complexity acquired by the iron crust dissolution (laterite) which has sustained the relief. Future studies concerning inland wetlands need to be carried out to certify the role of soil-landscape in the water cycle in the Savanna biome.

Highlighting the Potential of 3D ERT by Comparing its Results with GPR and the Excavation Map of a Roman Building

– Comparative measurements and analysis of 3D ERT and GPR results. – Evaluation of different ERT data processing methods.

Multi-Scale Geophysical Methodologies Applied to Image Archaeological Ruins at Various Depths in Highly Terraneous Sites

Among all geophysical techniques, electrical resistivity and magnetic surveying as an integrative approach has been used widely for archaeological prospection at different scales of investigations. In this study, DC resistivity (1D vertical sounding and/2D/3D ERT) and magnetic surveys (total and gradient) as a multi-scale approach was applied in a highly terraneous archaeological site (Tell) with a case study to characterize and image the various archaeological assets at different depths with different spatial resolutions. Four critical zones of great interest within the considered Tell were surveyed. At the heart of the study area, three layers were depicted clearly from 1D resistivity sounding. A thick conductive zone of mostly clay is sandwiched between two resistive layers. The topmost layer contains construction debris (dated back to the Islamic Era), whereas the deeper layer could be related to Gezira sand on which the probable Pharaonic temple was constructed. A long 2D ERT profile using Wenner Beta (WB) and Dipole–Dipole (DD) arrays with a 5-m electrode spacing identified shallow high resistivity anomalies that could be related to construction ruins from fired bricks. Additionally, it succeeded in imaging the turtleback-shaped deeper resistive layer of mostly sand. At an elevated rim to the east and west of the Tell, total and vertical magnetic gradient maps clearly delineated different archaeological structures: the walls of the rooms of ancient Islamic settlers and the walls of water tanks from the Byzantine Era. Magnetic modeling assuming 2.5-dimensional magnetic models constrained by the 2D ERT inversion models could be used to create a realistic representation of the buried structures. Toward the northern part of the Tell, the joint application of the quasi-3D ERT inversion scheme and the magnetic survey revealed an anomaly of a well-defined geometric shape of an archaeological interest thought to be a crypt or water cistern based on nearby archaeological evidence. The overall results of the geophysical survey integrated with the image of some partially excavated parts provided the archaeologists with a comprehensive and realistic view of the subsurface antiquities at the study area.

Imaging lateritic bauxite bearing zones in Ekiti, Southwestern Nigeria, using magnetic and electrical resistivity tomography techniques

This research uses geophysical techniques such as magnetic and electrical resistivity tomography to image the lateritic bauxite bearing zones in Orin Ekiti, Southwestern Nigeria. The high-resolution aeromagnetic data were utilized for generating the total magnetic intensity (TMI) map. Different filtering techniques such as Euler deconvolution and total horizontal derivative were also carried out to enhance better understanding of bauxite deposit, with the generation of different maps therein. Low magnetic intensities were observed over charnockitic rock which is a host material for bauxite occurrence. Magnetic low trending NE–SW was observed in the study area. The (EUD and THDR) maps were then superimposed on the geologic map to geo-reference areas that have dominant charnockite. The depth extent and structural signature interpreted from magnetic interpretations show that significant deposit in the study area is at shallow depth which tallies with the geology of bauxite as being a supergene enrichment (surficial deposit). 2D ERT results obtained from five traverses with inter-traverse separation of 45 m and traverse length of 100 m each, established in the NW–SE direction to image the lateritic bauxite deposit based on the prospect shown from the aeromagnetic analysis. The images display the constant resistivity regimes beneath the traverses with different colour bands. The 2D ERT profiles and 3D inversion results show bauxitic zones to be of high resistivity which ranges from 154 to 3814 Ω m, the migmatite gneiss and granitic rocks (unaltered parent rocks) are of considerably lower resistivity than the weathered charnockitic rock and by extension bauxitic zones. These different techniques used in this study have however shown that the area of interest for bauxitic deposit in Orin Ekiti trends in the NE–SW direction with a dominant concentration in the north-eastern (NE) part. By the same token, this research has been able to substantiate the fact that bauxite deposits occur as supergene enrichment.