Characterization of structurally complex granitic basement rocks using multi‐geophysical data: Insights into subsurface weathered bedrock zones and groundwater exploration

Abstract Globally, basement rocks cover a large portion of the land surface and are the primary source for the formation of soil and regolith, or the weathered bedrock zones where groundwater circulates freely. However, groundwater flow in basement rock aquifers is often irregular and complex due to the heterogeneous nature of the subsurface bedrock. This complexity underscores the importance of conducting detailed studies to better understand weathered bedrock zones and groundwater dynamics in granitic basement rocks. This study focuses on the granitic basement rocks in North Gujarat, India, examining the complexities associated with weathered bedrock zones and groundwater potentials. We employed a combination of multi‐geophysical techniques, Shuttle Radar Topography Missiondigital elevation model hill‐shaded imagery, and field observations to delineate subsurface weathered zones and identify potential groundwater sites. The analysis revealed significant structural lineaments, including faulting and fracturing, which contribute to the formation of weathered bedrock zones with enhanced porosity and permeability. Based on the field observations and structural features, the areas were classified into ductile (Zone‐A), brittle (Zone‐B) and brittle‐ductile (Zone‐C) zones, with the brittle‐ductile zones showing the most promising sites for groundwater exploration due to their dense fracture networks. Near‐surface geophysical methods, such as electrical resistivity tomography, very‐low‐frequency electromagnetics and magnetic surveys, were used to map the subsurface properties like resistivity and magnetic susceptibility. The results indicated that areas with low resistivity and low magnetic susceptibility are associated with weathered bedrock and transition zones, which have emerged as the most promising targets for groundwater exploration. Further, this study demonstrates that integrating multiple geophysical techniques improves the reliability of subsurface imaging and reduces the risk of misinterpretation, providing a comprehensive framework for identifying optimal sites for groundwater exploration.