Geophysical investigations for locating buried iron slag at Lejja, southern Nigeria

Archaeological geophysics involving the use of resistivity imaging and induced polarization (IP) techniques were used to locate buried iron slag and furnaces at Lejja, Southeastern Nigeria. The instrument used was the ABEM Lung measuring meter system, employing the Wenner electrode configuration. The acquired resistivity and IP data were processed and interpreted using Res2DINV software. The inverse resistivity models revealed the presence of relatively high resistivity materials of about 1090-2600Ωm buried at depths of 2.55-3.70m at different locations within the survey area. The inverse chargeability models are consistent with the inverse resistivity models in terms of the spatial locations of the buried materials. Materials of relatively high chargeability values of 2.09 – 3.09ms were also shown to have been buried at depths of 2.55-3.70m. These relatively high resistivity and chargeability materials were interpreted to be iron slag or burnt bricks used for the furnace by the iron smelting workers many years ago. Determination of the spatial distribution of the buried iron slag and furnaces helped to identify the most suitable locations, outside the region of the buried materials, where hand-dug wells can be sited.