Optimized electrical resistivity tomography investigation established in identifying pit tombs of Mogareb, a cemetery area in a Pre-Aksumite archaeological site of Seglamen, northern Ethiopia

Abstract

The larger area of Aksum is known as the most important archaeological areas in northern Ethiopia. It is included in the UNESCO World Heritage List as from about the IV century BC, it developed as one of several polities on the Tigrean plateau and emerged as the capital city of a powerful kingdom roughly between the II and the VIII centuries AD. The Mogareb is a cemetery in a Pre-Aksumite archaeological site of Seglamen located about 12 km South-West of Aksum.The geophysical survey was deployed to investigate the cemetery with the objective of finding and locating unmarked tombs. This work was also intended to test potential of the technique for the wider archaeological area of Aksum, in similar context to Mogareb, where application of geophysical techniques in multidisciplinary archaeological researches, in general, is not common.The approach in this work established an optimized use of the electrical resistivity tomography technique in understanding the archaeological context of the Pre-Aksumite site of Seglamen. The electrical resistivity tomography investigation of large cemetery sites as Mogareb requires a methodological approach designed to define areas of maximum interest where data collection should be planned. Thus, the ERT method suited the Mogareb cemetery area due to the large amount of apriory information from previous archaeological expeditions involving surface collections and excavations that identified and limit extent of the cemetery and were used in the calibration of geophysical survey results.The electrical resistivity tomography survey was conducted on a rectangular grid of 19.5 m by 44.25 m with 0.75 m unit electrode spacing and line spacing in a Dipole-Dipole configuration resulting in high resolvable 2D and 3D electrical resistivity model sections. The models were successful to show interpreted pit tombs anomalies some of which were verified in an excavation of a 10 m by 10 m grid that had an overlap of 6 m by 10 m area to the Northern edge of the electrical resistivity tomography grid.