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Internal architecture of coarse-grained barriers in hypertidal environments (France and Argentina): A GPR study

Abstract : Barrier spits and beach ridges are different types of coastal barriers controlled predominantly by wave dynamics. They represent the two end members of a continuum of wave-built features reflecting varying orientations of net sediment transport (longshore vs. cross-shore). In hypertidal environments, high amplitude tide-induced sea-level changes as well as strong tidal currents necessarily combine with wave action in the construction of spits and beach ridges. In this study, we image the internal architecture of two coarse-grained coastal barriers, both located in hypertidal environments: the mixed sand-and-gravel spit at the mouth of the hypertidal Somme estuary in the English Channel (Northern France), and the sand-and-gravel barrier systems at the inlet of the hypertidal Santa Cruz estuary in Southern Patagonia (Southern Argentina). Maximum tidal ranges are 9 and 11 m in the French and Argentinian sites respectively. A great variety of morphologies compose the two systems, from simple spits and barrier spits to beach ridges. Both sites were investigated using ground-penetrating radar (400 MHz GSSI antenna), along with the analysis of aerial photographs and digital elevation models. Cross-shore and long-shore profiles, with a penetration depth between 2 and 4 meters, show a large range of radar facies attributed to erosional surfaces, beachface progradation, along-drift elongation, hooks and spit terminus development, and washover deposits. The in-depth analysis of radar architecture allows reconstructing the development of individual morphology in the two systems, and helps to differentiate the influence of wave- and tide-related processes. The most open-sea barrier-spit systems (Somme estuary and Santa Cruz external mouth) show a classic development controlled by the wave-related littoral drift, probably enhanced due to shore parallel flood currents. In contrast, the most internal systems, located along the northern edge of the Santa Cruz inner inlet, feature contrasting morphologies, structures and directions of elongation, either landward or seaward, reflecting a complex balance between wave- and tide-dominated dynamics on their construction.
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https://hal-normandie-univ.archives-ouvertes.fr/hal-03283734
Contributor : Léo Pancrazzi Connect in order to contact the contributor
Submitted on : Monday, July 12, 2021 - 10:38:23 AM
Last modification on : Monday, July 19, 2021 - 10:04:54 AM

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  • HAL Id : hal-03283734, version 1

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Léo Pancrazzi, Bernadette Tessier, Pierre Weill, Dominique Mouazé, José Cuitiño, et al.. Internal architecture of coarse-grained barriers in hypertidal environments (France and Argentina): A GPR study. 35th IAS Meeting of Sedimentology, Jun 2021, Virtual, Czech Republic. ⟨hal-03283734⟩

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