The Applications of Analytic Signal Method in Archaeological Investigations of Part of Lejja Pre-historic Site, South-Eastern Nigeria

The attempt to properly date the iron-age Lejja site has been the concern of some archaeologists for the past few decades. The latest archaeological investigations of the area revealed that artefacts could be found at depths below one metre. Excavation of such completely concealed features may involve much futile digging which is prohibited at most locations in the community. To avoid discontinuity of the research resulting from environmental restrictions, we have adopted a more environmentally friendly approach; that is, geophysical mapping of the artefacts before excavation. Archaeo-magnetic data was acquired on regular 1 by 1 metre grid covering a total area of 2400 square metre using proton precession magnetometer (Geometrics model G-856AX). The analytic signal software used for inversion of the field data was first validated using synthetic data obtained from Rao and Babu model. The result revealed presence of some archaeological features, perhaps, a prehistoric iron smelting furnace and a mound nearby, both remaining in-situ and buried at same depth of 1.76 metres. Also revealed were two other smaller features which were, most likely, iron smelting slag blocks buried at depths of 1.2 and 1.56 metres. However, permission was not granted for excavations that were needed to confirm the above results.