The process of external molding of pebbles on the rocky substrate is called contact alveoli. These structures occur in the granite substrate as a result of the back of the Forte do Cão Conglomerates and Sands, the matrix, with some clay content, creates conditions of more intense chemical weathering in the clast environment, allowing the fossilization of its diameter. The identification of contact alveoli in coastal granitoids allows the reconstructing of the Forte do Cão Conglomerates and Sands paleocoverage.