The Pisan Castle of Gioiosa Guardia in Villamassargia (Sardinia). Archaeometric analysis of masonry

The Castle of Gioiosa Guardia in Villamassargia (Sardinia) is a classic example of a XIIIth century military fortress. It was located in a strategic position on top of the hill with the same name. It guarded and watched over the Cixerri valley, which was important due to its mineral resources. The fortress occupies several levels: halfway up are the ruins of buildings that very probably served as guardhouses, on top are the ruins of the castle itself, enclosed and protected by a perimetral curtain wall. The aim of this case study is to define the construction techniques used to build the fortress, which was constructed on the request of the Pisan unily, Della Gherardesca_ It was built in a single phase and abandoned, probably after just two centuries. It defined a type of wall, the Pisan style in Sardinia, in the late XIIIth century_ The clirono-typological definition of the walls took advantage of an interdisciplinary method through archaeometric analysis developed over three main phases: photogrammetric survey; archaeological investigation - deepening the knowledge of the formal, dimensional and technological aspects - and, finally, mineralogical and petrographic characterization of the natural and artificial stone materials, through the analysis of thin sections and x-ray diffractions. The study presented is part of a wider research with the aim of offering a contribution to the knowledge of the history of the traditional local building techniques, so that it is easier to recognize, date and preserve all the buildings which, unlike the one examined, are not philologically dated. 1 INTRODUCTION The lack of studies for the dating of historical buildings in Sardinia, recently led the Chair of Restoration at the University of Cagliari to start research on traditional masonry techniques for each sub-regional area, with reference to the period between the VI' and the XIXth centuries (Giannattasio, 2008). The aim is to define chronological classes, starting from philologically dated architectures useful to deepen knowledge about, and consequently favour, the conservation of historic buildings (Giannattasio, et al., 2015). In this sense, the defensive structures, such as urban and suburban walls, fortresses, castles, defence and lookout towers, arc well suited to being chronological benchmarks. The present work, focusing on the Gioiosa Guardia Castle in Villamassargia (Sardinia -Italy), is part of a specific investigation on fortified systems in the Cagliari and Arborca Ciindicati (Xth-XVIli century), which are located in the South of Sardinia. Mensiochronological investigations of the masonry techniques used in this architecture allowed us to define chronological markers, with specific dimensional constants and material characteristics. The results are useful elements with which to build a regional knowledge framework of traditional masonry techniques, that could easily and quickly allow the recognition of 'minor' buildings, usually difficult to date and therefore to protect