Management of An Aquatic System Using a Morphoscopic and Exoscopic Approach: The Case of the Ebrie Lagoon System (Coast of Côte d’Ivoire)

The morphoscopic and exoscopic analysis of quartz grains from the eastern sector of the Ebrié lagoon made it possible to determine the environment and reconstruct the sediment deposition environments. To achieve this objective, sediment samples were taken using a Van Veen grab and positioned by a GPS. They are washed with hydrochloric acid. Dry sieving produces medium quartz grains (0.5 - 0.25 mm). The selected quartz grains are observed under a scanning electron microscope (SEM). The morphoscopic study showed angular, sub-rounded to rounded quartz grains with blunt and shiny contours. Coming from the Mé, Comoé rivers, the Adjin and Potou lagoons, these sediments were transported at low energy over a very long distance before being deposited in the study area. Exoscopic examination of quartz grains from the sediments revealed large breaks on the surface of the quartz grains. Several shock trails are also visible and spread over the entire surface of the quartz grains. The presence of observed breakage and impact marks is the origin of the numerous movements of the quartz grain over a very long distance in a very agitated environment. The traces of chemical action identified are dissolution cavities and silica deposits. The strong presence of dissolution figures would facilitate the diffusion of silica and reveal the sedimentary history of the area. The quartz grains underwent torrential and marine fluvial transport.？