首页|Coastal chalk cliff retreat rates during the Holocene, inferred from submarine platform morphology and cosmogenic exposure along the Normandy coast (NW France)

Coastal chalk cliff retreat rates during the Holocene, inferred from submarine platform morphology and cosmogenic exposure along the Normandy coast (NW France)

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  • NSTL
  • Elsevier
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 Be-10 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.

Coastal cliffsChalkErosionRock platformHoloceneCosmogenic dating

Duguet, Timothee、Duperret, Anne、Costa, Stephane、Regard, Vincent、Maillet, Gregoire

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Normandie Univ, UNILEHAVRE, CNRS, UMR 6294 LOMC, 53 Rue Prony, F-76600 Le Havre, France

Normandie Univ, UMR 6554 LETG Caen, UNICAEN, CNRS, F-14032 Caen, France

Univ Toulouse, CNES, UPS, GET,CNRS,IRD, 14 Av Edouard Belin, F-31400 Toulouse, France

Univ Angers, CNRS, UMR 6112 LPG Angers, 2 Blvd Lavoisier, F-49000 Angers, France

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2021

10.1016/j.margeo.2020.106405

Marine Geology

Marine Geology

EISCI
ISSN：0025-3227
年,卷(期)：2021.433
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  • 108