Late Holocene seacliff retreat recorded by 10Be profiles across a coastal platform: Theory and example from the English Channel |
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| Institution: | 1. Université de Toulouse, UPS (OMP), CNRS, IRD, GET, 14 Av. Edouard Belin, F-31400 Toulouse, France;2. BRGM, Risques Naturels, F-45060 Orléans, France;3. Aix Marseille Univ., CEREGE, UMR CNRS 6635, BP 80, 13545 Aix en Provence, France;4. University of Colorado at Boulder, Department of Geological Sciences, Institute of Arctic & Alpine Research – INSTAAR, UCB 450, Boulder, CO 80309, USA;5. UMR 6294 LOMC CNRS, Université du Havre, Laboratoire Ondes et Milieux Complexes, 53 rue de Prony, BP540, 76058 Le Havre, France;6. Université Caen Basse Normandie, Geophen, CNRS, LETG, UMR 6554, F-14032 Caen, France;7. UMR CNRS 6143 Morphodynamique Continentale et Côtière (M2C), Université Caen Basse Normandie, 2-4 rue des Tilleuls, 14000 Caen, France;8. Faculté des Sciences, Université d’Angers, 02 Bd Lavoisier, 49045 Angers cedex 01, France;1. Mediterranean Institute for Advanced Studies (IMEDEA), Esporles, Spain;2. Collecte Localisation Satellites (CLS), Space Oceanography Division, Ramonville Saint-Agne, France;3. Toulouse Space Centre (CST), Centre National d’Etudes Spatiales (CNES), Toulouse, France;4. Balearic Islands Coastal Observing and Forecasting System (SOCIB), Palma de Mallorca, Spain;1. Department of Communicable Diseases Control, Jiangxi Provincial Center for Disease Control and Prevention, 555 Beijing East Road, Nanchang 330000, Jiangxi, China;2. Department of Infectious Diseases, The First Affiliated Hospital, Nanchang University, #17 Yongwai Zheng Street, Nanchang 330006, Jiangxi, China;3. Department of Epidemiology and Biostatistics, School of Public Health, Nanchang University, 461 Bayi Road, Nanchang 330006, Jiangxi, China;4. Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, 81 Meishan Road, Hefei 230032, Anhui, China;5. Department of Infectious Diseases, The Second Affiliated Hospital of Anhui Medical University, Hefei 230032, Anhui, China;6. Jiangxi Provincial Cancer Hospital, 519 Beijing East Road, Nanchang 330029, Jiangxi, China |
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| Abstract: | We explore a new method for documenting the long-term retreat rate of seacliffs based on measurements and modeling of 10Be concentration transects across present-day shore platforms. The proposed forward numerical model relies on a scenario of sea-level rise since the last deglaciation, and predicts the shape of 10Be concentration transects as a function of prescribed cliff recession and vertical coastal platform downwearing rates. Two independent transect features allow fitting the long-term recession rate model to field observations: a sharp 10Be concentration drop predicted at the former stationary location of the cliff during the last glacial period ∼100 ka ago, and a characteristic dome shape whose magnitude is directly related to the recession rate of the cliff. A retreating chalk cliff site from the English Channel coast of France, at Mesnil-Val, where the 7 m tidal range broadly exposes the shore platform, was selected to test the proposed method. Although retreat rates were too high to pinpoint the predicted 10Be concentration drop at the last glacial cliff position, the 10Be concentration of the flints sampled across the shore platform is consistent with the expected dome shape. When modeled using the proper tidal range and proposed Holocene sea-level rise history, the 10Be data yield a cliff retreat rate since the mid-Holocene of 11–13 cm/yr. This is consistent with a 30-year-long measurement record, strongly supporting the utility of the 10Be method. |
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