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

  • Martins Olusola Olorunfemi
  • Benjamin Adisa Ogunfolakan
  • Ademakinwa George OniEmail author
Research Report

Abstract

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.

Keywords

Igbo Oritaa Iwo (southwest Nigeria) Geophysical investigation Community archaeology 

Résumé

Une étude géophysique intégrée a été réalisée à Igbo-Oritaa, une banlieue de la ville d’Iwo (sud-ouest du Nigéria). L’étude faisait partie d’une enquête archéologique initiée par la communauté pour identifier et préserver les sites ancestraux de la ville. Les études géophysiques ont porté sur l’établissement de profils magnétiques au sol, le sondage électrique vertical 1D et l’imagerie de résistivité électrique 2D. Les cartes magnétiques ont identifié des anomalies aux caractéristiques archéologiques présumées: des anomalies ressemblant à des dykes (basse magnétique centrale [négative]flanquée d’épaules positives de faible amplitude); dépressions linéaires avec des dépressions magnétiques d’amplitude négative importantes; et une anomalie magnétique d’amplitude modérée qui coïncidait avec une ancienne tranchée et plusieurs monticules anthropiques. Ces caractéristiques ont été corroborées par les cartes de résistivité en tant que zones de résistivité faible ou élevée. Les unités d’excavation ont été sélectionnées en fonction de ces attributs géophysiques. Les fouilles ont mis au jour des dépôts denses de tessons de poterie, d’os d’animaux, de coquillages, de perles, de scories de fer, d’une prémolaire humaine, d’objets métalliques, d’une flûte, et d’un élément architectural, éventuellement la fondation d’une maison. Les levés géophysiques et les fouilles expérimentales confirment qu’Igbo Oritaa était une ancienne colonie, conformant aux traditions orales. Cette articlea examiné les relations entre la prospection géophysique et les fouilles archéologiques, ainsi que les implications pour la conception de la recherche archéologique communautaire, ainsi que pour l’interprétation et la préservation des sites historiques.

Notes

Acknowledgments

The authors are grateful the paramount ruler, His Royal Majesty, Oba Abdulrasheed Adewale Akanbi, the Oluwo of Iwo who, through the Iwo Historical and Cultural Association (IHCA), invited us to carry out archaeological research in Igbo Oritaa. Messrs. T. K. Fadare and E. A. Adewale participated in the geophysical data acquisition. The authors are also grateful to the two anonymous reviewers whose comments have helped us improve the quality of the manuscript.

Funding Information

We thank the Iwo Historical and Cultural Association for financing the geophysical investigation, archaeological excavations, and site preservation effort.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of GeologyObafemi Awolowo UniversityIle-IfeNigeria
  2. 2.Natural History MuseumObafemi Awolowo UniversityIle-IfeNigeria

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