The Itanhaém Formation is a geological formation of the Santos Basin offshore of the Brazilian states of Rio de Janeiro, São Paulo, Paraná and Santa Catarina. The predominantly shale formation with marls, siltstones and sandstones dates to the Early Cretaceous period; Early Albian epoch and has a maximum thickness of 1,500 metres (4,900 ft). The formation is the reservoir rock of the Tambaú Field in the Santos Basin.