Late Holocene archaeobotanical evolution of the Canale di Imbocco (Roman imperial port of Portus, Central Italy)

The Roman port of Portus was the most important in the Mediterranean during the imperial period (27 BC–476 AD). It was made up of an outer port or Claudius basin and an inner hexagon or Trajan's port, joined by the Canale di Imbocco. The archaeobotanical record obtained in a continuos sediment core taken in this channel is made up of 19 types of plant macroremains, with a predominance of fibers of the seagrass Posidonia oceanica L., replaced by fluvial sediments in the upper part of the core. Seeds, fruits and thorns of aquatic species from marine or brackish waters, halophyte species, edible species, freshwater riparian vegetation and remains of charcoal and wood also appear regularly. According to the inferred palaeoenviromental evolution of this core, Portus was an area of fluvial-marine interaction during the Roman Empire, with brackish water conditions interrupted by stormy periods deduced from the record of P. oceanica. The archaeobotanical and sedimentary evolution points to a restriction of marine contributions and a final implantation of a fluvial environment. In this evolution, a specific interval with abundant charcoal and caryopses of Triticum could correspond to a fire, which was followed by a possible period of greater construction activity linked with large fragments of wood.