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Évolution environnementale holocène dans l'estuaire de la Seine : Juliobona et la vallée du Bolbec/Commerce
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Edité par CCSD ; Association paléontologique de Villers-sur-Mer -
Riverine and coastal sedimentary archives are indicative of environmental change through time and provide clues to understanding environmental adaptation in response to forcing, whether climato-eustatic and/or anthropogenic. They can also be used to elucidate human-environment relationships and socio-environmental co-evolution. This article focuses on the Holocene sedimentary archives of the Seine estuary along the lower valley of the Rivière du Commerce, in the vicinity of Juliobona, the capital of the city of the Caletes. The proximity of the sea and rivers, whether the Seine or the Channel, allowed this Roman city to prosper, articularly through trade. A more detailed comprehension of the sedimentary filling would facilitate the identification of the environmental contexts preceding and contemporaneous with the ancient occupation. The working hypothesis is based on the displacement of the Seine's shoreline over the centuries. In order to study the succession of sedimentary deposits and gain insight into the pace of landscape transformation, a multidisciplinary geoarchaeological approach has been developed. This approach combines geophysical surveys, sediment coring, dating, abiotic sedimentological analysis and biotic palaeoenvironmental analysis. The phasing, constructed on the basis of the initial results, indicates the succession of a marine/coastal environment (upper limit: ca. 2,387 cal. BP), then a brackish environment and finally a freshwater environment (lower limit: ca. 2,064 cal. BP). The data presented here offer a new vision of environmental evolution in the Commerce valley, in the vicinity of the Roman town of Juliobona. They also prompt us to reconsider previous hypotheses which envisaged a later clogging of the valley.