Cross Analysis of Morphological Evolution and Internal Architecture of an Active Mixed Sand-Gravel Barrier Spit (Somme Bay, Northern France)
| Autor: | Bernadette Tessier, S. Le Bot, Léo Pancrazzi, Pierre Weill, Laurent Benoît |
|---|---|
| Přispěvatelé: | Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), EC2CO DRIL (CNRS/INSU) - GIPSIeS |
| Rok vydání: | 2020 |
| Předmět: |
Washover
010504 meteorology & atmospheric sciences GPR [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph] Stratigraphy Spit Global change 010502 geochemistry & geophysics 01 natural sciences Oceanography Morphodynamic [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy Natural hazard Berm Coastal barrier Mixed Sand-and-Gravel [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology 14. Life underwater Architecture Bay Geology 0105 earth and related environmental sciences |
| Zdroj: | AGU 2020 Fall Meeting AGU 2020 Fall Meeting, Dec 2020, Virtual, United States. ⟨10.1002/essoar.10505396.1⟩ |
| DOI: | 10.1002/essoar.10505396.1 |
| Popis: | International audience; Morphodynamic evolution of coastal barriers and the way it is recorded in the internal structure are still revealing many uncertainties. Coastal spits have a high potential of preservation due to their fast elongation under littoral drift, and are thus suitable for this kind of study. Compared to sandy spits, gravel and mixed spits are understudied. Yet these coarse-grained coastal barriers are sensitive sedimentary bodies due to the high energy conditions they are usually associated with and to often scarce sediment supply. The present study focus on the relationships between multi-decadal morphological evolution of a mixed sand and gravel spit in the bay of Somme (Northern France) and its sedimentary architecture. A geophysical survey using a 400 MHz GPR GSSI antenna have been performed on the Molliere spit, a fast-growing secondary spit developing along the main 15 km-long Somme barrier spit. The development of this sedimentary body starts in the 1940s and allows a morpho-stratigraphical approach, thanks to the cross analysis of aerial photographs and GPR profiles. The spit is 5 km long and is composed of several ridges, sometimes with hooks at the tip. A synthetic depositional and stratigraphical model specific to gravel spits is proposed, based on radar profiles and aerial photographs analysis, differentiating three contrasting morpho-sedimentary units. The Unit 1, at the spit root, is characterized by mainly progradating structures that can be assimilated to a beach ridge. The Unit 2, in the central part of the spit, is characterized by individual ridges with a core structure reflecting a longshore development, topped by an aggradating unit associated to a cross-shore-dominated dynamics. The third unit, at the spit terminus, is also mainly characterized by longshore dynamics, but interfering with sand bank dynamics due to the proximity of the Somme estuary and the development of the spit platform. Larger-scale GPR prospecting, especially in older coast sections, will be necessary to understand how this fast secondary spit development (decadal to centennial time scale) is integrated into the longer-term (millennial) construction dynamics of the main Somme spit. |
| Databáze: | OpenAIRE |
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