Assessing anthropogenic impacts on the landscape configuration of coastal areas of Corsica (France) from Early Neolithic to Late Roman times

Abstract

We present the first reconstruction of the landscape evolution of the coastal lowlands of the Island of Corsica, in the western Mediterranean, together with the identification of the first human impacts on both vegetational and morphological changes in some of the island¿s major river mouths. We performed a bio-stratigraphic analysis of a new set of boreholes drilled in saltmarshes and lagoons located in the SE (Bonifacio-Piantarella and Porto Vecchio-San Ciprianu sites), NW (Saint Florent) and in the central-eastern (Aleria-Del Sale) coast of the Island. We reconstructed the paleoenvironmental history of the last eight millennia in these areas, which are amongst the earliest settled areas of Corsica. The laboratory analyses of the borehole cores comprised: i) ostracods , which support and refine facies characterization and the turnover of depositional environments; ii) pollen grains, which enable us reconstruct the local vegetation history; iii) radiocarbon dating of 20 samples of organic matter, peat, marine and lagoonal shells which provides a robust chronostratigraphic framework for each site; and iv) XRF core scanning of the Saint-Florent core, drilled within a deltaic context, which provides a record of continental sediment detrital input. The principal results highlight the development of a Mediterranean maquis, together with a riparian forest, in the coastal plains of the island since at least early Neolithic times (ca. 5500 cal. BCE). The first signs of human influence appear in SE Corsica around 5450 cal. BCE (Early Neolithic) with the identification of Cerealia-type pollen and coprophilous fungi; while in the NW part of the island, the pollen data indicates human impacts on the vegetation since ca. 3300 cal. BC. Archaeological records from the Bonifacio area do not suggest any early agricultural activity. By contrast, in the Saint-Florent area, archaeological finds in the 1980s provided evidence of agricultural practices since ca. 3300 cal. BC (Mid Neolithic times), which is in good agreement with our pollen record. Surprisingly, at all sites there is minimal evidence of agricultural activity during the Roman period. From a paleogeographic perspective, the sedimentological analyses combined with the meiofaunal identifications (ostracods) indicate that major shifts in the shoreline position occurred during key archaeological periods: The first and most significant deltaic progradation occurred around 3500 cal. BC, and it can be related to the sudden decrease in the postglacial sea-level rising rates observed at the Mediterranean Sea. A second phase of major deltaic progradation occurred around 2200 cal. BC in the Aleria-Del Sale and Saint-Florent areas. This date corresponds to the well known 4.2 ka RCC event and also to the shift from the Chalcolithic to the Bronze Age in Corsica. By combining all the proxies, we try to disentangle the climatic and anthropogenic influences on major sediment discharge at the river mouths.