Depositional controls on a hypertidal barrier‐spit system architecture and evolution, Pointe du Banc spit, north‐western France

Mikkel Fruergaard (1) , Bernadette Tessier (2) , Clément Poirier (2) , Dominique Mouazé (2) , Pierre Weill (2) , Suzanne Noël (3)

1 GEUS - Geological Survey of Denmark and Greenland
2 M2C - Morphodynamique Continentale et Côtière
3 HisTeMé - Histoire, Territoires et Mémoires

Physical stratigraphy, architecture and evolution of barrier systems in hypertidal environments (tidal range above 6 m) are understudied, and depositional controls are poorly understood compared with wave‐dominated barrier systems and barrier spits in microtidal, mesotidal and macrotidal settings. Based on vibracores, ground‐penetrating radar, radiocarbon and optically stimulated luminescence age data, the formation and evolution of the hypertidal barrier system of Pointe du Banc, north‐western France has been reconstructed. The study shows that the barrier spit has a complex composite sedimentary architecture consisting of wave‐dominated and tide‐dominated sedimentary bodies. A morpho‐sedimentary model is presented that demonstrates how barrier‐spit progradation resulting from littoral drift was the main manner of spit elongation, whereas sediment convergence caused by landward migration of swash bars and seaward migration of tidal dunes caused the spit terminus to grow in height and width. These results suggest that long‐term accretion rates varied considerably in response to changes in sediment supply. Variations in storminess together with the large‐scale topography of the coast controlled the sediment supply and thus the evolution of the barrier system during latest Holocene. Despite architectural complexity, hypertidal barrier systems preserve records of past climate changes.

Mots clés: depositional controls; ground‐penetrating radar; optically stimulated luminescence dating; ground-penetrating radar; North-West France; Coastal evolution; North‐West France; increased storminess and sediment supply

Domaines: Stratigraphie; Géomorphologie; Géophysique [physics.geo-ph]; Interfaces continentales, environnement

Mikkel Fruergaard, Bernadette Tessier, Clément Poirier, Dominique Mouazé, Pierre Weill, et al.. Depositional controls on a hypertidal barrier‐spit system architecture and evolution, Pointe du Banc spit, north‐western France. Sedimentology, 2020, 67 (1), pp.502-533. ⟨10.1111/sed.12652⟩. ⟨hal-02376512⟩