GNGTS 2014 - Atti del 33° Convegno Nazionale

The municipal area of Costigliole Saluzzo mainly lies on quaternary deposits mainly consisting of fluvioglacial and fluvial sediments (Pleistocene-Holocene) of the big alluvial fan apparatus of the Varaita River that opens towards the plain with slight slop (about 1%). The deposits are mainly made by medium-to-coarse gravels with a sandy matrix and a wide variety of pebbles and blocks of variable size, resulting from the erosion of the lithologies of the whole valley, can also be found. The alluvial deposits in the archaeological site show on the surface the presence of centimetric to decimetric pebbles. In the exploratory trenches and excavations, however, the soil seems mainly consisting of silt and clay down to about 3 m. Therefore most of the pebbles are likely due to the destruction of the ancient walls and structures. The Roman remain walls, in fact, are largely made up of these natural pebbles and blocks. From a visual expeditious analysis on the field, the pebble lithology is largely represented by serpentinites and metabasites, probably outcoming from the Monviso Massif. Monviso serpentinites consist of antigorite and magnetite, with subordinate brucite, Mg-chlorite, tremolite, diopside, Ti-clinohumite and haematite (Balestro et al. , 2011; Castelli and Compagnoni, 2007). Magnetite grains are generally heterogeneously distributed in the serpentine matrix but locally they appear aligned to form thin bands that cross rocks following preferential directions (Compagnoni and Fiora, 1976). Geochemical analysis of the bulk rock composition shows a very high percentage of iron oxides, variable from 6% to more than 13% (Hattori and Guillot, 2007). The archaeological context. The ruins of a wide villa rustica (Fig. 2) belonging to the Roman imperial period (Ist to IIIrd centuries AD) were unearthed by the University of Turin at the southern periphery of modern Costigliole Saluzzo and are still under excavation (Barra Bagnasco, 2003, 2005; Barra Bagnasco and Elia, 2007; Elia and Meirano, 2008, 2008-2009, 2012a, 2012b; Elia, et al. , 2013). After the destruction and the abandonment of the settlement, an occupation of the site is attested during the late-antique period (IVth-Vth centuries AD). The area, showing structures and erratic ancient materials, extends over ca 3 hectares. Measuring ca 56 x 85 m in its major phase, the main building reaches an extent of around 5000 m 2 . The explorations carried out in the last few years allow for the identification of a “U-shaped” villa characterized by a clearly-defined plan which represents an unicum in western Gallia Cisalpina so far. The evidence recovered supports the identification of the functions of the different sections of the building, with regard to both the pars rustica and the pars urbana . The main body is situated in the eastern part and shows an anomalous extent for this kind of buildings. The western part consists in a wide court (more than 1200 m 2 ) delimited by two long wings. These wings were destined to stocking agricultural products and to housing the Fig. 2 – Plan of the villa (left) and picture of the walls unearthed after earlier excavation campaigns (right). 192 GNGTS 2014 S essione 3.2