Mid- to Late-Holocene coastal morphological evolution, vegetation history and land-use changes of the Porto Gulf UNESCO World Heritage site and its surroundings (NW Corsica Island, Western Mediterranean)

Résumé En

Two coastal areas located on the North-Western side of Corsica Island have been investigated to reconstruct their Mid- to Late-Holocene landscape evolution together with the history of human occupation. Particular attention has been paid to the study of shoreline migration and vegetation history alongside land-use. Three boreholes were drilled to a maximum depth of 4.20 m and laboratory work comprised the identification of molluscs and pollen/NPPs as well as sedimentological analyses. Chronostratigraphy is based on a series of 18 radiocarbon datings and enabled to reconstruct the environments in the Fangu Estuary to the north of the World Heritage site over the last six millennia, and over the last four millennia on the Girolata coastal plain to the south. Palaeogeographic reconstruction of shoreline mobility is established for each site based on borehole chronostratigraphy analysis. In addition, two original pollen and NPPs diagrams have been established for the Girolata and Fangu sites. These reveal that anthropogenic activities began to significantly impact local vegetation cover ca. 2500 years BP at Girolata, and ca. 2000 years BP at Fangu. Of particular interest, our work records the first complete pollen sequence in Corsica for Roman times at Girolata: first, the exploitation of cereals, grapevines and the development of husbandry is observed during the Roman Republic (500 BCE–0), followed by the almost exclusive cultivation of Olea sp. during the Roman Empire (0–500 CE). Following this, and using other regional pollen studies obtained for NW Corsica, we propose a regional evolution of the complex human-environment interactions for the last six millennia. Our results reveal a peak of regional forest decline (the most intense event recorded for the Late-Holocene) from the 11th to the 16th centuries CE which can be attributed to the exploitation of wood resources during the Pisan and Genoese dominations of the island.