Abstract
Banco Bay, within the Ebrié Lagoon system of southern Côte d’Ivoire, contains sandy substratum deposits whose sedimentological characteristics remain insufficiently documented. While previous studies have largely focused on superficial lagoonal sediments and present-day sedimentary dynamics, limited information is available on the grain-size properties of the sandy deposits forming the bay’s substratum. Characterising these deposits is therefore important for improving understanding of their sedimentary features and depositional conditions. The studies conducted on the sandy facies of the substratum of Banco Bay aim to characterise the sandy levels of the bay using grain-size parameters and the interpretations derived from them. The methodologies used for this characterisation consisted of determining grain-size parameters, namely quantiles, quartiles, mean, mode, standard deviation, skewness, and kurtosis. The parameters were calculated using the classical method of moments. The main grain-size analyses made it possible to identify quasi-coarse sands throughout all the wells studied, indicating a moderate to turbulent palaeocurrent in the environment. Poorly sorted sands are more abundant than moderately sorted sands in all the boreholes studied. This sorting of the sands may be attributed to the currents that transported them. The currents were somewhat more regular for the moderately sorted sands, whereas the poorly sorted sands were transported by irregular currents. The curves are almost unimodal in all the wells. The results of these curves indicate one main sediment source supplying the entire bay. Skewness is generally positive, indicating that there are more grains with sizes greater than the mean. The different kurtosis values show a slight overall predominance of leptokurtic distributions across the tabulated samples. The grain-size parameters determined made it possible to characterise the sandy levels identified in the substratum of Banco Bay. These findings contribute to a better understanding of the coastal sedimentary basin, particularly the sands deposited on the bottom that form the substratum of the bay.