Characterization of subsurface lithology based on resistivity grain gradation data in Mon Ikeun, Village, Aceh Besar, Indonesia

Abstract

To address the growing challenges of water resource management in coastal karst areas, this study investigated subsurface lithological characteristics and evaluated aquifer potential in Mon Ikeun Village, Aceh Besar. The research integrated Electrical Resistivity Tomography (ERT) and grain size gradation analysis to provide a scientific basis for sustainable groundwater exploration. Resistivity data were collected along three survey lines, each 420 m long, using the Wenner-Schlumberger configuration. The 2D inversion results identified conductive zones with resistivity values below 454 Ωm, interpreted as alluvium comprising sand, silt, and gravel. These high-porosity, permeable layers extend to depths of approximately 25 m, indicating significant aquifer potential. In contrast, resistive zones above 454 Ωm were interpreted as limestone bedrock, representing impermeable layers with very low porosity. Laboratory grain size analysis using the hydrometer method revealed sand-dominated samples with high porosity (25-50%) and moderate permeability (2.5-45 m/day), while gravel-sand mixtures displayed moderate porosity (25-40%) and high permeability (150-450 m/day). The strong correlation between resistivity data and grain size distribution confirms the consistency of the lithological interpretation. This integrated approach offers an effective framework for securing freshwater resources in regions with complex geological settings and high vulnerability to water scarcity.