OSL and radiocarbon-based chronology of sand-drift events on Beniguet island (W France)
2023
Stéphan, Gillian | Stéphan, Pierre | Guérin, Guillaume | Onfray, Marylise | Pailler, Yvan | Nicolas, Clément | Littoral, Environnement, Télédétection, Géomatique (LETG - Brest) ; Université de Brest (UBO)-Université de Rennes 2 (UR2)-Institut Universitaire Européen de la Mer (IUEM) ; Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG) ; Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN) ; Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (Nantes Univ - IGARUN) ; Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Nantes Université - pôle Humanités ; Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ) | Géosciences Rennes (GR) ; Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des sciences de l'environnement de Rennes (OSERen) ; Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Trajectoires - UMR 8215 ; Université Paris 1 Panthéon-Sorbonne (UP1)-Centre National de la Recherche Scientifique (CNRS) | Department of Physics, Technical University of Denmark (DTU Physics) | ANR-21-CE27-0024,GEOPRAS,Géoarchéologie et préhistoire des sociétés atlantiques(2021) | ANR-17-EURE-0015,ISBlue,Interdisciplinary Graduate School for the Blue planet(2017)
International audience
显示更多 [+] 显示较少 [-]英语. Sand dunes are an essential component of coastal landscapes. The understanding of their long-term mobility is crucial to design appropriate management methods, especially in a context of global sea level rise and associated coastal erosion. Along the coasts of Western Europe, the mor-phological evolution of coastal dunes has been characterized by several periods of stability and remobilization of aeolian sands during the last millennia of the Holocene. Well-constrained chro-nologies of dune mobility periods have been reconstructed in Ireland, UK, Portugal based on radi-ocarbon dating of palaeosols interbedded in aeolian sand deposits. In western France, the absence of palaeosols has limited such approaches. Recently, archaeological and historical remains have been used but such an approach has many methodological limitations.The objective of this study is to provide robust chronological evidence for the Holocene mo-bility of coastal dunes in western France. It focuses on the chrono-stratigraphic analysis of the sandy cover of Béniguet Island, located at the western tip of the Brittany peninsula (W France). The geometry of the coastal sedimentary deposits was reconstructed about 40 vibro-cores taken from aeolian sands covering the central part of Béniguet Island over a thickness between 2 and 4 m, near an archaeological site currently being excavated. Four archaeological levels were identified and dated to the Bell Beaker, Early Bronze Age, High Middle Ages and Late Middle Ages periods.The chronology of the Holocene deposits is based on a dozen radiocarbon dates obtained on the anthropogenic levels and on 8 Optically Stimulated Luminescence (OSL3) ages obtained on the aeolian sand layers. Equivalent doses were mesured from multi-grain aliquots and the dose rate was obtained from high resolution gamma spectrometry. The chronology of the sequence was modeled by combining OSL ages and radiocarbon dates in a Bayesian framework using the R package BayLum4. The anthropogenic levels are overlain by a series of aeolian sand layers dated by OSL to ca. 4000 BP, 2700 BP, 1000 BP. These results are consistent with the regional chronology established for western France and clarify the timing of coastal sand-drift events.
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