Holocene salt-marsh sedimentary infilling and relative sea-level changes in West Brittany (France) using foraminifera-based transfer functions

Pierre Stéphan (1) , Jérôme Goslin (1) , Y. Pailler (1) , Rose Manceau (2) , Serge S. Suanez (1) , Brigitte van Vliet-Lanoë (3) , Alain Hénaff (1) , Christophe Delacourt (3)

1 LETG - Brest - Littoral, Environnement, Télédétection, Géomatique
2 LGP - Laboratoire de géographie physique : Environnements Quaternaires et Actuels
3 LDO - Domaines Océaniques

In order to reconstruct the former sea-levels and to better characterize the history of Holocene salt-marsh sedimentary infillings in West Brittany (western France), local foraminifera-based transfer functions were developed using Weighted-Average-Partial-Least-Squares (WA-PLS) regression, based on a modern dataset of 26 and 51 surface samples obtained from salt-marshes in both the bay of Tressseny and the bay of Brest. Fifty cores were retrieved from Tresseny, Porzguen, Troaon and Arun salt-marshes, which were litho- and biostratigraphicaly analyzed in order to reconstruct palaeoenvironmental changes. A total of 26 AMS 14C age determinations were performed within the sediment successions. The Holocene evolution of salt-marsh environments can be subdivided into four stages: (1) a development of brackish to freshwater marshes (from c. 6400 to 4500 cal. a BP); (2) salt-marsh formation behind gravel barriers in the bay of Brest (from 4500 to 2900 cal. a BP); (3) salt-marsh erosion and rapid changes of infilling dynamics due to the destruction of coastal barriers by storm events (c. 2900-2700 cal. a BP); (4) renewed salt-marsh deposition and small environmental changes (from 2700 cal. a BP to present). From the application of transfer functions to fossil assemblages, 14 new sea-level index points were obtained indicating a mean relative sea-level rise around 0.90±0.12 mm a-1 since 6300 cal. a BP.

Mots clés: Sea-level change; Holocene; France; Foraminifera; Salt-marsh; Transfer function

Domaines: Géomorphologie

Pierre Stéphan, Jérôme Goslin, Y. Pailler, Rose Manceau, Serge S. Suanez, et al.. Holocene salt-marsh sedimentary infilling and relative sea-level changes in West Brittany (France) using foraminifera-based transfer functions. Boreas, 2015, 44 (1), pp.153-177. ⟨10.1111/bor.12092⟩. ⟨hal-01021995⟩