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<p>The Langue de Barbarie (LDB), located off the coast of Saint-Louis (Senegal), is a rapidly evolving sand spit. To understand how its formation, it is crucial to define the continental or marine origin of the sediments and to pinpoint their sources. An emerging methodology (Elemental composition of Sediment frActions—ELSA) based on particle geochemical analysis of each sediment grain class was used. Different geochemical markers were used: Zr/Ti for the fine fractions (100–160&#xa0;μm) rich in heavy minerals, Si/Zr for the medium fractions (200–315&#xa0;μm) dominated by quartz and Ca, which characterizes marine shell inputs, for the coarse fractions (400–630&#xa0;μm). Compositional end-members were defined and used to calculate the proportions of continental and marine sources for sediments from each of seven LDB stations and five reference stations. Our study proposes a three-phase construction sequence. The initial phase (construction of the tip) was dominated by river inputs, the second was dominated by the Senegal River, the amplification of marine inputs and longshore drift, whereas the third phase (maturation) was dominated by longshore drift linked to frequent and strong oblique swells. Our results confirm the importance of the latter processes during the elongation of the spit.</p>

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Construction Process of the Langue de Barbarie in Senegal, Based on the Identification and Quantification of Fluvial and Marine Sources: Application of the New ELSA Geochemical Methodology

  • 期刊论文

  • 发表日期：

    2025年3月26日

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  • Gwendoline Gregoire,
  • Anne Murat,
  • Thierry Garlan,
  • Pierre Shute,
  • Carla Labarthe,
  • Régis Gallon,
  • Clément Frigola,
  • Yann Méar,
  • Timothée Nivet,
  • Maëlle Le Moäl

摘要

The Langue de Barbarie (LDB), located off the coast of Saint-Louis (Senegal), is a rapidly evolving sand spit. To understand how its formation, it is crucial to define the continental or marine origin of the sediments and to pinpoint their sources. An emerging methodology (Elemental composition of Sediment frActions—ELSA) based on particle geochemical analysis of each sediment grain class was used. Different geochemical markers were used: Zr/Ti for the fine fractions (100–160 μm) rich in heavy minerals, Si/Zr for the medium fractions (200–315 μm) dominated by quartz and Ca, which characterizes marine shell inputs, for the coarse fractions (400–630 μm). Compositional end-members were defined and used to calculate the proportions of continental and marine sources for sediments from each of seven LDB stations and five reference stations. Our study proposes a three-phase construction sequence. The initial phase (construction of the tip) was dominated by river inputs, the second was dominated by the Senegal River, the amplification of marine inputs and longshore drift, whereas the third phase (maturation) was dominated by longshore drift linked to frequent and strong oblique swells. Our results confirm the importance of the latter processes during the elongation of the spit.