Buried landscapes: Geoarchaeology of the Roman harbor of Como (N Italy)

The town of Como (N Italy) was founded in 59 BC on the shores of the homonymous lake. Its present-day environmental setting derives from the interactions between lacustrine, alluvial and human dynamics. The lake coastline moved through time because of alluvial progradation, town expansion and land reclamation. Since 1700 AD, more than 200 m of land reclamation towards the North are observed from historical maps of the study area. The harbor is a strategic infrastructure for a coastal town and its localization is a critical issue. Archaeological evidence found in the Como urban area points to a different position of the harbor during the Roman period and the Middle Ages; presently, those areas are buried below several meters of sediments due to land subsidence and the artificial filling of coastal areas. The results of a geoarchaeological study aimed at understanding the evolution of the coastal area are presented here. Adopted methodologies include the collection of available archaeological and stratigraphic data and the analysis of a number of continuous core drillings both on the lake promenade and, for the first time in Como, on the lake bottom. Sedimentological and geotechnical investigations were performed and archaeological and vegetal findings were studied. A lithological unit consisting of organic silts rich in vegetal remains and archaeological findings has been identified. The thickness of this unit varies from less than 1 meter to 6 meters and it refers to a depositional environment characterized by shallow water and human influence; its deposition started during Roman Age, when the town was founded and an impressive reorganization of the drainage network took place. Geological cross-sections and map reconstructions enable us to define different phases of the town evolution. Our results highlight the role of geological research in reconstructing the recent evolution of buried and/or submerged environments: geoscience provides useful information when it is not possible to carry out expensive archaeological excavations at sensitive sites and allows to optimize resource utilization