Geophysical and Archaeological Survey in Igbo Oritaa (Iwo), Southwest Nigeria

An integrated geophysical survey was carried out in Igbo Oritaa, a suburb of Iwo town (southwest Nigeria). The study was part of an archaeological investigation initiated by the Iwo community to identify and preserve the town’s ancient sites. The geophysical investigations involved ground magnetic profiling, 1D vertical electrical sounding (VES), and 2D electrical resistivity imaging. The magnetic survey revealed anomalies of dyke-like features (central magnetic low [negative] flanked by low amplitude positive shoulders), linear depressions with prominent negative amplitude magnetic lows, and a moderately high amplitude magnetic anomaly coinciding with an old trench and several anthropogenic mounds. The resistivity survey also indicates the presence of subsurface archaeological features, including ditches and walls. Excavation units were selected based on these geophysical attributes. The excavations uncovered dense deposits of potsherds, animal bones, shells, beads, iron slag fragments, a human premolar, metallic objects, a flute, and an architectural feature, possibly the foundation of a house. The geophysical survey and the test excavations confirm that Igbo Oritaa was an ancient settlement, consistent with the oral traditions. This paper presents the geophysical methods and results, the relationships between geophysical prospecting and test excavations, as well as the implications for community-focused archaeological research design, and site interpretation and preservation.