Unveiling ancient maritime secrets through X-ray computed tomography (CT): Iron-based finds from the archaic shipwreck of Giglio-Campese

In August 1961 the remains of a shipwreck, dating back to the early 6th century BCE, were located at the Island of Giglio in the Bay of Campese (Tuscany, Italy), announcing a major archaeological discovery. Meticulous excavations carried out in the early 1980s partly brought to light both the exceptionally diverse cargo and structural remnants of the vessel. Owing to the extremely heterogeneous composition of the load of international scope, ranging from Etruscan to Greek productions, this finding reflects and testifies to the complexity of archaic trade networks across the Tyrrhenian Sea in the early 6th cent. BC. Within the framework of a broad multidisciplinary collaboration involving several institutions and experts, X-ray computed tomography (CT) was employed to investigate the hidden history of the ship and, by extension, aspects of our own cultural past. Among the numerous notable artifacts, the analysis concerned some heavily corroded and fragmented iron-based objects, whose original shape and function are no longer legible due to severe degradation and thick layers of concretions. To reconstruct their original morphology and thus identify the type of artifacts, two dedicated measurement campaigns were carried out in the X-ray imaging laboratory of the University of Bologna, Ravenna Campus (Emilia-Romagna, Italy), using a custom-designed CT system, equipped with a 200 kVp X-ray tube and a flat-panel detector with 127 µm pixel size. More than 20 tomographic scans were performed with a voxel size of about 100 µm, producing a substantial dataset for subsequent processing. The virtual removal of calcareous incrustations allowed us to formulate several hypotheses about the typology and function of the investigated artefacts. Preliminary interpretations have been proposed based on the observation of quadrangular cross-sectional profiles that originally contained metallic cores. These cores are now entirely or almost entirely consumed by corrosion, leaving only a layer of mineralized concretion with little to no metal preserved. Elemental composition was further assessed through complementary X-ray fluorescence (XRF) analyses, performed on selected points of the finds, supporting our investigation. Although the objects recovered from the depths of the Tyrrhenian Sea survive only as “ghosts” of their originals, the integration of CT imaging, visual inspection and XRF results has contributed to shed light on the ship’s cargo composition of Greek and Etruscan provenance as well as on its route’s stages.