Morphoscopy of Sandy Sediments in Intertidal Areas along the Gulf of Guinea: A Case Study in Cote d'Ivoire

Kouame Moise Kouassi, Aoua S.Coulibaly, Saimon Aby Atse Mathurin, Koffi Marcellin Yao

Abstract: This study focuses on the influence of the transport mode on the shape of sandy sediments along the Ivorian intertidal zone (Assinie: 05?07'45.3''; 003?17'06.3'' to the Ivorian-Liberian border: 04?21'47.8''; 007?31'36.7''). 159 sediment samples were collected and the 630 ?m, 250 ?m, and 160 ?m fractions were taken into account. The granulometric analysis identified two facies? sequences, all with a decreasing grading in the direction of the littoral drift (West-East). The first sequence starts from the Ivorian-Liberian border at Monogaga village (San-Pedro region); and the second from Sassandra town to Assinie town (Ivorian-Ghanaian border). The Ivorian-Liberian border sites contain coarse sediments and the stations in the Monogaga area (San-Pedro region) record medium-sized sediments. However, in Sassandra, the sites show very coarse sediments and those in Assinie show fine sediments. The cumulative semi-logarithmic curves describe sigmoid facies. The main mode of transport of quartz in this study area is by saltation, with a mainly monogenic source. Sediment saltation in the direction of the littoral drift leads to a pronounced polishing of the coarse fractions compared to the fine fractions.

Keywords: intertidal zone, morphoscopy, granulometry, littoral drift, mode of transport