Late Holocene Palaeoenvironmental evolution and human settlements in the Adige River Plain (Italy)

This multidisciplinary research aims to understand the palaeohydrographical and palaeoecological evolution of the distal part of present-day Adige alluvial plain (north-eastern Italy) and man-environment relations during the Late Holocene. The area is of great archaeological interest for an exceptionally well-preserved roman centuria, which extends for 250 km2 from the city of Rovigo almost to the Lagoon of Venice and important Bronze and Iron Age sites: among them, Roman-Age villa of Ca’ Motte, very close to the decumanus maximus of the centuriation area, situated on the top of a crevasse-splay deposits and Saline placed on the alluvial ridge of the Philistina Po palaeochannel, characterized by an archaeological stratigraphy with Bronze, Iron and Roman age remains. The investigation takes advantage of microrelief and historical cartographic analyses, remote sensing and boreholes down to the depth of 5-7 m with the Edelman hand auger. In order to quantify the organic content of the peat, loss-on-ignition technique has been adopted. Palaeobotanical analyses of the peat layers have been carried out to establish the vegetation assemblage of the swamp environment. The radiocarbon dating of the backswamp peats helped to date the fluvial activity in this area which consists of Late Holocene fine sediments. The classical geomorphological studies have been supported by some petrographical analyses of the drilled sands in order to determine the composition and to compare it with the Adige and Po sediments. As a consequence each sand body has been related to the appropriate fluvial basin. A digital elevation model has been developed, based on a manual interpolation of spot heights with spacing of 0.5 m of the “Carta Tecnica Regionale del Veneto” at scale 1:5000. Landsat TM and Aster images let the analysis of major landforms while oblique and vertical panchromatic photo-aerial interpretation gave a finer detection of natural morphologies and anthropic structures. Stratigraphical cross-sections of the main alluvial ridge have been carried out, in order to clarify the space-time relations between human settlements and palaeoenvironment since the Bronze Age. A complicated web of palaeochannels incised the alluvial plain through the millennia; its sedimentary history is characterized by periods of aggradation due to the upbuilding of fluvial ridges and crevasse splays alternated with periods when overbank clays and peats accumulated with lower depositional rates. Cross-sections also suggest that the position of the ancient settlements is not casual. In fact, they located in places characterized by high geomorphological conditions and good drainage.