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Stable isotopic approach on mollusk shells to paleoenvironmental reconstitution: Study of an urban site: Lyon (France)

Abstract : The human settlement and development of the city of Lyon since Antiquity have been partly controlled by the topography of the site, particularly by the presence of the Saone and the Rhône rivers, which enclosed the peninsula. Bivalves and few gastropods shells have been collected from archaeological levels, to conduct an extensive δ18O and δ13C study. In fact, malacofauna shells potentially record, during the growth period, the impact of the major hydrological and climatic changes on the aquatic ecosystem. The study is focused on two extreme climatic periods: the Medieval Climate Optimum and the Little Ice Age. A third, less documented period, corresponds to the High Roman Empire (Antiquity). The shells were collected from several sites on the peninsula: both near the left bank of the Saone river, close to the old confluence area and near the right bank of the Rhône river; on the Fourvière hill near the right bank of the Saone. The isotopic data are close to those of the modern Saone water and modern mollusk shells from the river. This seems to indicate a privileged use of the alluvial deposits of the Saône river for human activity. Temperatures of the water were estimated between 17.2°C and 18.5°C. An average paleotemperature difference of nearly 1.3°C is observed between the MCO and the LIA. The shells of the High Empire record intermediate temperatures (18.1°C). The δ13C of Middle Age shells suggest more favorable climatic period (warming and decreasing flows) and episodes of swirling and paludification of the banks. This study shows the importance of the geochemical record from the mollusk shells as a climate archive with high temporal resolution (year), on the continent and particularly in urban areas. This latter can be indeed characterized by rapid and frequent variabilities and the disappearance of many markers due to human activity.
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Contributor : Laurence Le Callonnec Connect in order to contact the contributor
Submitted on : Thursday, May 12, 2022 - 9:27:17 AM
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Laurence Le callonnec, Stéphane Gaillot, Juliette Belavoine, Fabien Pons. Stable isotopic approach on mollusk shells to paleoenvironmental reconstitution: Study of an urban site: Lyon (France). Archeosciences, revue d'Archéométrie, G.M.P.C.A./Presses universitaires de Rennes, 2019, pp.7-26. ⟨10.4000/archeosciences.6084⟩. ⟨insu-03665723⟩



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