Geoelectrical Resistivity and Geological Characterization of Hydrostructures for Groundwater Resource Appraisal in the Obudu Plateau, Southeastern Nigeria

Electrical resistivity tomography (ERT) and vertical electrical sounding (VES) techniques were employed to assess the hydrogeological structures and groundwater potential of the Obudu Basement Complex. The Wenner electrode configuration was used to acquire the ERT data along 4 profiles, while the Schlumberger configuration was employed in the VES investigation, where 30 locations were occupied during the data acquisition campaign. Results show that rock distribution is predominantly the granite gneiss series that are considerably weathered in several locations especially within the western portion of the study area. Three potential hydrogeological scenarios were identified from three of the ERT profiles. These include the regolith-, doleritic- and kaolin-induced groundwater conduits. Within the central segment of the study area, transtensional stress regimes traceable to the neo-Proterozoic syn-orogenic event were observed to have resulted in the establishment of some regional fault systems. Over time, several episodes of minor tectonic events have resulted in cataclastic deformation of the gneissic rocks, creating pathways for groundwater circulation. Additionally, it was observed that dolerite intrusion in some locations cataclastically deformed the host rock resulting in syn-emplacement fractures that can create pathways for groundwater to flow. Saprolite units and locations within major fault lines were inferred to have moderate to good groundwater potential due to their large width and the presence of multiple interconnected fractures as inferred from the pseudo-sections and lineament map. More so, streams and rivers within these areas can infiltrate through the pathways created by the faults, hence increasing groundwater circulation within the conduits.

Automated summary

ERT and VES techniques were used to assess hydrogeological structures and groundwater potential in the Obudu Basement Complex. The study revealed the presence of granite gneiss series with potential groundwater conduits and regional fault systems created by transtensional stress regimes from the neo-Proterozoic syn-orogenic event.