Geomagnetic and geoelectrical prospection for buried archaeological remains on the Upper City of Amorium, a Byzantine city in midwestern Turkey

Abstract

On the basis of geophysical imaging surveys, including geomagnetic and geoelectrical resistivity, possible archaeological remains and their spatial parameters (i.e., location, extension, depth and thickness) were explored to provide useful data for future excavations on the Upper City of the ancient Amorium site, which comprises a large prehistoric man-made mound. The surveys were performed very close to the main axis of the Basilica, and the derived geophysical traces indicated some subsurface structures that appear to confirm that more-substantial brick and masonry buildings lie near the present-day surface of the mound. Analyzing the local gradients by total horizontal derivatives of pseudogravity data enhanced the edges of the magnetic sources. Additionally, a profile curvature technique, which has rarely been applied to potential field data sets, dramatically improved the magnetic-source body edges and the lineaments that may be associated with buried archaeological remains. The depths of these possible anthropogenic remains were estimated by applying the Euler deconvolution technique to the geomagnetic data set. The Euler solutions on tentative indices indicated that the depths of the source bodies are not more than about 3 m. Moreover, geoelectrical resistivity depth slices produced from the results of two- and three-dimensional linearized least-squares inversion techniques revealed high-resistivity anomalies within a depth of about 3 m from the ground surface, which is in close agreement with those obtained by applying the Euler deconvolution technique to the magnetic data. Based on the existence of some archaeological remains in the vicinity of the surveyed area, these geophysical anomalies were thought to be the possible traces of the buried remains and were suggested as targets for excavations. This study also emphasized that the data-processing techniques applied in this investigation should be suitable for providing an insight into the layout of the unexcavated parts of the Amorium site.