Dynamics, Evolution, and Facies Preservation of a Microtidal Chenier Plain, Joal-Fadiouth (Senegal, West Africa)

Abstract

Youm, C.I.; Morales, J.A.; Doumbouya, M.F.; Garcia-Villalba, E.; Sow, I.S., and Sow, E., 2023. Dynamics, evolution, and facies preservation of a microtidal chenier plain, Joal-Fadiouth (Senegal, West Africa). Journal of Coastal Research, 39(2), 257–265. Charlotte (North Carolina), ISSN 0749-0208. Cheniers are coarse sediment ridges formed above finer sediments deposited on a tidal flat, the origin and development of which have traditionally been attributed to storm waves. Joal-Fadiouth is a microtidal system located on the southern coast of Senegal (West Africa). This system presents a succession of sandy and shelly ridges displaying a facies architecture consistent with a chenier plain facies model. This study combines aerial orthophotographs and sediment cores to interpret the sedimentary dynamics and facies of the chenier plain under analysis. The genesis of the last active chenier is related to the arrival of sand from the frontal ebb-tidal delta. Breaching processes occurred in the ebb delta, inducing the abandonment of the frontal lobe by the ebb-tidal currents. Fair-weather waves rework the sand from the frontal lobe, causing a migration of the sand in a manner similar to the formation of a typical nearshore swash bar. In Joal-Fadiouth, these bars soar and migrate over a tidal flat through the action of normal waves during spring high tides. Relict cheniers present shelly gravel sediments coarser than those observed in active cheniers. Thus, the final stage of stabilization of cheniers was attributed to the action of more energetic storm waves. The cheniers that accumulate during the action of ordinary and continuous processes tend not to persist, and only the coarsest cheniers formed during high-energy events finally remain in the sedimentary record. In addition to discussing the preservation of active coastal forms, this work is of regional interest, given that so far there has been only one work on cheniers in West Africa since 1989.