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

Research areas:

• Systèmes marins en transition

Year:

2021

Keywords:

Coastal cliffs, Chalk, Erosion, Rock platform, Holocene, Cosmogenic dating

Authors:

• Timothée Duguet
• Anne Duperret
• Stéphane Costa
• Vincent Regard
• Grégoire Maillet

Journal:

Marine Geology

Volume:

433

Pages:

106405

ISSN:

0025-3227

BibTex:

@article{DUGUET2021106405, author = "Timoth{\'e}e Duguet and Anne Duperret and St{\'e}phane Costa and Vincent Regard and Gr{\'e}goire Maillet", 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.", doi = "https://doi.org/10.1016/j.margeo.2020.106405", issn = "0025-3227", journal = "Marine Geology", keywords = "Coastal cliffs, Chalk, Erosion, Rock platform, Holocene, Cosmogenic dating", pages = "106405", title = "{C}oastal chalk cliff retreat rates during the {H}olocene, inferred from submarine platform morphology and cosmogenic exposure along the {N}ormandy coast ({NW} {F}rance)", url = "https://www.sciencedirect.com/science/article/pii/S0025322720302930", volume = "433", year = "2021", }

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.