Coastal chalk cliff retreat rates during the Holocene, inferred from submarine platform morphology and cosmogenic exposure along the Normandy coast (NW France)
Type | Article | ||||||||||||
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Date | 2021-03 | ||||||||||||
Language | English | ||||||||||||
Author(s) | Duguet Timothée1, Duperret Anne1, Costa Stéphane2, Regard Vincent3, Maillet Grégoire4 | ||||||||||||
Affiliation(s) | 1 : Normandie Université, UMR 6294 LOMC, CNRS, UNILEHAVRE, 53 rue de Prony, Le Havre 76600, France 2 : Normandie Université, UMR 6554 LETG-Caen, CNRS, UNICAEN, Esplanade de la Paix, Caen 14032, France 3 : Université de Toulouse, GET, CNRS, IRD, UPS, CNES, 14 Av. Edouard Belin, Toulouse 31400, France 4 : UMR 6112 LPG-Angers, CNRS, Université d’Angers, 2 boulevard Lavoisier, Angers 49000, France |
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Source | Marine Geology (0025-3227) (Elsevier), 2021-03 , Vol. 433 , P. 106405 (23p.) | ||||||||||||
DOI | 10.1016/j.margeo.2020.106405 | ||||||||||||
WOS© Times Cited | 9 | ||||||||||||
Keyword(s) | Coastal cliffs, Chalk, Erosion, Rock platform, Holocene, Cosmogenic dating | ||||||||||||
Abstract | Submerged marine terraces potentially provide crucial information on past sea-level variations and paleo-coastline locations that may be used to estimate long-term coastal erosion rates. The Normandy coastline has recently been surveyed using a shallow water high-resolution mapping system. We identified a new continuous submarine platform, called the inner platform, limited by a shore parallel edge located between -9 m and -10 m (NGF) along the Normandy chalk coastline. A lower rock platform, called the outer platform, ranging from about -14 m to -17 m (NGF) appears locally. This corresponds to inherited preserved submarine terraces created during a past sea level highstand. The high cosmogenic 10Be concentration measured at the end of Mesnil-Val inner shore platform (including intertidal and subtidal shore platforms) is attributed to the last glacial cliff location at 6.5 ky ± 1 ky. From the spatial edge location of the inner platform in Normandy, we estimated cliff retreat rates since 6.5 ky ± 1 ky ranging from 0.051 ± 0.008 m/y to 0.090 ± 0.014 m/y from place to place. Comparisons with the current coastal chalk cliffs indicate a mean retreat rate estimated over the contemporary period suggesting such long-term retreat rates are 33% to 57% lower than the contemporary ones (0.10 m/y to 0.18 m/y). This confirms a contemporary acceleration of chalk cliff system retreat rates. |
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