Provenance analysis of sands in beach-dune systems of the islands of Boa Vista (Cape Verde archipelago)

Abstract

The island Boa Vista (Cape Verde), of volcanic origin and located in the North Atlantic, features a combination of volcanic materials and carbonate sediments, resulting from the interaction between a complex magmatic evolution and more recent sedimentary processes. This study analyzes the provenance and composition of sands from various beaches and eolian deposits across the island, aiming to better understand its sedimentary dynamics and assess potential environmental implications associated with coastal development amid the growing tourism industry of archipelago. A total of 20 sand samples were collected from subtidal, intertidal, supratidal, and aeolian environments throughout the island. Petrographic analysis was conducted using thin-section microscopy, classifying grains into lithoclasts, bioclasts and intraclasts. The results show that the sediments are predominantly biogenic (average 79.4%), composed mainly of red algae and mollusk fragments, indicating a strong influence of marine biogenic production from shallow platforms typical of mature islands. Subsequently, the intraclasts are the next most abundant group, with an average of 17.4%. Finally, lithoclasts, although present in significantly lower proportions (average 3.2%), are mostly mafic in nature, derived from the basaltic formations. The compositional uniformity of the sands across the island supports the hypothesis of an interconnected dune system driven by coastal and aeolian processes, with the northern insular platform as the primary source of sediment. These findings highlight the importance of preserving the northern coast to maintain sediment transport balance and mitigate anthropogenic impacts on these fragile environments