Occurrence of storm-generated bedforms along the inner continental shelf: Southeastern Brazil

Abstract

Side-scan sonar surveys were carried out in two different areas on the inner continental shelf off the state of Espírito Santo (southeastern Brazil, Area 1- Guarapari Inner shelf -GUA and Area 2- Espirito Santo Bay - BES) and revealed bedforms much like those known as storm-generated bedforms. These bedforms are characterized by bands of fine sand deposited alternately over a coarse sand bottom, generating a deposit pattern of bands of fine sand intercalated with bands of coarse sand occurring between water depths of 25 to 30 m and five to eight m in GUA and ESB, respectively. In both areas, patches of coarse sand reveal the occurrence of wave-generated ripples, with crests that tend to be parallel to the coastline. The facies composition consists of very fine to fine muddy carbonate sands with siliciclastic fine gravel in GUA and coarse to medium sand with bioclastic gravel in BES. Thus, the influence of storm currents and waves in the formation and maintenance of these storm-generated bedforms is clear. However, the classification of the hydrodynamics and sediment transportation is required for estimating the formation, transportation and maintenance of these bedforms.