Geoarchaeological analysis of the early mediaeval site of Vetricella (Southern Tuscany, Italy): Site formation processes and circular ditches

Vetricella is a mediaeval archaeological site located within the coastal plain of the river Pecora (southern Tuscany, Italy). The settlement consists of a fortified mound with a raised central rectangular tower -like building surrounded by three concentric ditches. This paper presents the results about geoarchaeological stratigraphy and site formation processes and provides new important information regarding the foundation of the settlement, its occupational phases and its abandonment. Field data and micromorphological observation show that Vetricella was settled on a relict palaeosol characterised by an argillic Bt horizon covering the top of the Upper Pleistocene alluvial fan. The latter was already hanging over the floodplain, thus providing a safe and relatively dry place to overcome the hydraulic hazard. The main occupational phases of the settlement are characterised by continuous operations of raising and levelling, constantly modifying or removing pre-existing surfaces. On the other hand, the geometry and backfilling of the three concentric ditches are the result of a high engineering design and management for the use of spaces, resources and activities of the settlement. The last phase of occupation of the settlement is marked by the spoliation of the central tower -like building and the levelling of the entire surface of the archaeological site. No evidence of natural driven processes responsible for the abandonment has been observed, due to the long-term stability of the alluvial fan surface.