GPR Survey on the Etruscan “Frontone della Tarantola”

Coli M.,  Donigaglia T., Ciuffreda A. L., Mariotti, P. I., Simoni G., Morandi D.

Abstract

The “Frontone della Tarantola” is a stone solid-panel detached in 1904 from the tympanum of the back-side of an VI century B.C. tomb in the Etruscan necropolis of Monterozzi, Tarquinia (VT, Italy necropolis, in the Tarantola farm area. Since then, it is conserved at the Archaeological National Museum at Florence (Italy. The whole necropolis was dig in local soft holocenic calcarenite called Macco. The pediment (Frontone has a trapezoidal shape of 3.5 x 1 m and 14-18 cm thick. On the front side there is a mural painting representing a banquet with four men recumbent on a mattress and a fair; below there is a continuous frieze of 13 bands of alternating colours. In order to ensure stability and strengthen the detached stone-panel, it was enclosed by a wooden framework and lined on the back first with a mortar made with the local Macco as then by a layer of concrete. Four vertical iron bars link the upper and lower wooden beams. After the detachment the Tarantola pediment was subject to some restorations, but recently it presented same cracks and was in need of a new restoration, recently done at OPD. DST and IDS GeoRadar supported OPD for a GPR surveying addressed to identify the thicknesses of the stone-panel, mortar lining and concrete layer, and the 3D network of the cracks. GPR survey consisted into 4 horizontal scan-lines, vertically spaced, running all along the entire length of the front side. Georadar data has been implemented into a 3D model content, that allowed a full 3D georefencing of the analysis for a correct interpretation. Georadar data allowed tomographic analysis that led to map in 3D the cracks and outlined in the right side of the pediment the concave shape, up to a depth of about 5 cm, of a previous gypsum integration. Georadar tomography and punctual analysis led to recognized the interface between surficial weathered Macco, intact Macco, mortar and concrete. The layers thickness resulted in the order of: weathered Macco 3 cm, intact Macco 3 cm, mortar 6 cm, concrete up to 4 cm. The results of the Georadar survey largely supported the designing of the restoration interventions on the Tarantola Etruscan pediment.