Archaeological geophysics: 3D imaging studies at Muweilah, United Arab Emirates (UAE)

Abstract

The sand covered Muweilah archaeological site in the United Arab Emirates (UAE) is a unique Iron Age site, and subject to intensive excavation. However, this time consuming process would require up to 20 years to complete. This paper presents preliminary results of geophysical surveys with the ultimate objective of characterising the site far more quickly. Ground penetrating radar (GPR) was trialed as a primary imaging tool with a very shallow time domain EM (MetalMapper) system in a supporting role. Dense 3D GPR datasets were migrated at 10 cm intervals to produce horizontal (plan view) slices which are conceptually similar to the excavation methodology used by archaeologists. The objective here was to delineate extensive linear and planar features. In addition, isolated scatterers were classified. Finally, MetalMapper images were used to discriminate between metallic and non metallic scatterers. The highly resistive sand cover provided GPR depth penetration of up to 5 m. GPR successfully mapped floor levels, walls and isolated anthropogenic activity, although in some cases crumbling walls were difficult to track. From this study two possible courtyard areas were recognised. The MetalMapper was less successful due to the limited depth penetration of 50 cm. Despite this, the system was still useful in detecting modern day ferruginous waste and bronze artefacts. The results (subject to ongoing ground-truthing) indicated that GPR was optimal for sites like Muweilah, which are buried under a few metres of sand. The 3D survey methodology proved essential to achieve line to line correlation for tracking walls. Although MetalMapper surveys were not as useful as hoped, they certainly indicated the value of including other geophysical data to constrain interpretation of complex GPR features. Practically, a significant improvement in data quality accrued when survey areas were flattened and de-vegetated.