The Marambaia Formation (Portuguese: Formacão Marambaia) 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 and marl formation dates to the Tertiary period and has a maximum thickness of 2,700 metres (8,900 ft).

The formation is a seal and reservoir rock of the Atlanta and Oliva Fields in the Santos Basin.

The formation is named after Restinga da Marambaia, Rio de Janeiro.

[2] The formation is a seal,[3] and reservoir rock in the Atlanta and Oliva Fields of the Santos Basin.