Before Rome: Salt, settlement, and human–environment dynamics at the Early Iron Age site of Piscina Torta (Tyrrhenian coast)

Through an integrated geoarchaeological and palaeoenvironmental approach, we explored the origin, evolution, and anthropogenic modification of the Piscina Torta, a palaeochannel running across a beach ridge complex in the southern Tiber delta, from the inland Ostia palaeolagoon towards the sea. This channel was assumed to have played an important role in the activities at the connected Early Iron Age archaeological site of Piscina Torta, known for its salt production by briquetage. The research combines a range of methods and techniques: transect corings, high-resolution LiDAR mapping, electrical resistivity tomography (ERT), sedimentological and granulometric analyses, microfossil and plant macroremain studies, and AMS radiocarbon dating. These revealed that the base of the channel is in marine sands that form part of the early beach ridges in this area. Its fill consists of 1) highly calcareous marls that were deposited in a fresh water lake/lagoon, with a water level that ultimately reached to at least 1 m a.s.l. and dates from before the period in which the site was occupied (late 8th BCE); 2) peats formed over a long period (5th century BCE till modern times) and in an increasingly aquatic environment after the site was abandoned; 3) anthropogenically reworked sediments of modern age, containing abundant ancient ceramic fragments, likely consisting of surface materials, dumped to improve the drainage and trafficability of the area. During the late 8th to 6th century BCE, the marls in the central part of the channel were excavated, creating an anthropogenic channel (canal), which potentially had a connection with the sea in its lower, most seaward section of which the stratigraphy remained obscure, probably due to later coastal erosion. In the more inland section, which is situated within the large archaeological site, its base was distinctly above the contemporary sea level, implying that the channel/canal did not function as an open hydrological connection between the inland lagoon and the sea during the site’s occupation and more recent times. The period in which the site was occupied corresponds to significant socio-economic transformations in Central Italy and the emergence of Rome as a regional power. The study provides new insights into the interplay between coastal geomorphology, resource exploitation, and early state formation, emphasizing the role of environmental engineering in sustaining specialized production activities in dynamic coastal landscapes.