干旱区生态环境知识资源中心

The west coast of Corsica includes a series of freshwater ponds and coastal marshes which are located in the lower river valleys, at a short distance from the river mouths. The origin and the morphodynamic evolution of these wetlands have seen little investigation from both geomorphological and palaeoenvironmental perspectives while the archaeological context is well documented, in particular for the periods ranging from the Early to the Late Bronze Age. Archaeological research indicates that probable changes in landscape configuration occurred during the second half of the 2nd millennium BC, leaving the river valleys unsuitable places for human occupation: only megaliths with humanlike faces are found, while the habitats are mainly situated on the upper slopes of the valleys. Until now, this question has never been evaluated by geomorphologists and palaeoenvironmentalists. Here, geoarchaeological research aims to evaluate the dynamics of human settlement around the wetlands within the lower river valleys. The objective is therefore founded on the need to better understand their morpho-sedimentary evolution during Mid-Holocene via correlation with hydroclimatic oscillations and an assessment of their impact on the dynamics of human occupation and resilience. With these issues in mind, two major Corsican river valleys, comprising Bronze Age archaeological evidence, have been investigated: the Sagone and the Taravo rivers. Palaeoenvironmental methods comprise the coring of four boreholes drilled in three different ponds. Palaeontological identifications (ostracods and foraminifera) combined with mollusc analyses helped identify the different environments. The sedimentological analyses are based on a granulometric study (LASER method) and the measurements of the magnetic parameters (magnetic susceptibility and thermomagnetism) of both, the sediments derived from the cores and the whole Taravo river drainage basin. Finally, a series of twenty-seven radiocarbon dates were taken, and these facilitated the creation of a robust chronostratigraphy for each site. The most relevant results reveal that an increase of marine incursions (storm events notably) is recorded between 1650 and 1100 cal. BC for both lower valleys. In parallel, an important fluvial and torrential detritism is observed from 1300 to 1000 cal. BC, this created an induced silting up of some ponds. Both extreme events (that were initiated during Mid Bronze Age and that continued during the first phase of Late Bronze Age) can be explained by regional climate variability observed at around the 3.2 ka BP: a cold and arid RCC event in the Mediterranean within a context of high anthropisation of the slopes from the southwest river valleys of Corsica.