Multi-Electrode Resistivity Tomography for Mapping Archaeological Sites and Buried Cultural Features at Igbo-Ukwu, Anambra State

Igbo-Ukwu is of exceptional archaeological significance as the site of a ninth-century bronze-working culture in southeastern Nigeria, and continued non-invasive investigation is essential for the protection and understanding of unexcavated cultural heritage. This study employs multi-electrode electrical resistivity tomography to detect and map buried archaeological structures and cultural features at Igbo-Ukwu, Anambra State. Six ERT profiles totaling 720 m were acquired across previously unexcavated areas adjacent to the known archaeological deposits using a 72-electrode Lund system with 2 m electrode spacing. Both Wenner and dipole-dipole configurations were employed to optimize resolution and depth penetration. Two-dimensional inversion was performed using RES2DINV, and resulting tomograms were interpreted in the light of the known stratigraphy from previous excavations. Localized high-resistivity anomalies (greater than 350 ohm-m) within a depth interval of 0.5 m to 3 m are interpreted as clusters of compact bronze artefacts, burned surfaces, or compacted occupation deposits. Low-resistivity anomalies (less than 10 ohm-m) at comparable depths reflect pit fills and midden deposits enriched in organic matter and moisture. Two subsurface anomaly clusters exhibit spatial patterns consistent with burial chambers or storage pits, based on comparison with resistivity signatures of the excavated Igbo Richard and Isaiah pits. The delineated anomaly clusters are proposed for targeted excavation in a phased approach. This study provides a template for non-invasive archaeological survey in southeastern Nigeria.

Keywords: electrical resistivity tomography, archaeological geophysics, Igbo-Ukwu, cultural heritage, buried features