Couplage d'archives sédimentologiques et historiques pour étudier 150 années d'évènement extrêmes dans la lagune de la Petite mer des Gâvres, France

Abstract : (The poster is in French language) This study exposes a 150 years high-resolution record of extreme wave events from a multi-proxy analysis of sedimentary deposits from a coastal depositional environment of the Western French coast. We analyze the Petite Mer de Gâvres lagoon, a wetland located behind a sandy barrier, where evidence for strong extratropical storms have been identified since 1850. Four short sediment cores were collected in August 2016 using a Beeker gravity corer from two different sites into this lagoon. Sediments were extracted behind a thick and a thin section of the sandy barrier to compare different stormy impacts depending on their environment. High-resolution elemental analyses of sediment cores were done using an Avaatech XRF core scanner, and X-radiographs were taken using a Scopix system. With the high resolution sediment sampling of 0.5 cm, grain size analysis was done using a Malvern 2600 laser beam grain sizer. We also tested to find new geochemical proxies testifying marine intrusions in the Petite Mer de Gâvres, as previous attempts to define geochemical indicators of past storms for the European Atlantic coast are missing in literature. These new proxies then helped us in the identification of sedimentological washovers.137Cs and 210Pb dating has been proceeded from measurements of 2 g dried sediment using a low background, Camberra well-type γ spectrometer. Combined with our dense historical resources, these strong events have been associated with the precise date of past storms that impacted the study site, with important details about the damages caused by these events. The historical information has been researched using archives including narrative sources, surveys conducted after a disaster, newspapers from different departmental and national archives, and meteorological data from Meteo France. Results show that in the Petite Mer de Gâvres, six extreme episodes can be observed, including an 1896 AD intense washover due to a violent extratropical storm that may have breached the sandy barrier of the Petite Mer de Gâvres lagoon.
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https://hal.archives-ouvertes.fr/hal-01890230
Contributeur : Pierre Pouzet <>
Soumis le : mercredi 12 décembre 2018 - 12:22:10
Dernière modification le : jeudi 7 février 2019 - 17:40:36

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CHIA_Pouzet_LQ.pdf
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Pierre Pouzet, Mohamed Maanan, Sabine Schmidt, Emmanuelle Athimon, Marc Robin. Couplage d'archives sédimentologiques et historiques pour étudier 150 années d'évènement extrêmes dans la lagune de la Petite mer des Gâvres, France. Coastal Hazards In Africa, Oct 2018, Tetouan, Maroc. 〈http://coastalhazardsafrica.uae.ma/site/〉. 〈10.13140/RG.2.2.17764.83848/1〉. 〈hal-01890230〉

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