Guarujá Formation

The Guarujá Formation (Formacão Guarujá) 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 calcarenite formation with marls dates to the Early Cretaceous period; Early Albian epoch and has a maximum thickness of 2500 m. The formation is the second-most important post-salt reservoir rock of the Santos Basin.

Etymology
The formation is named after the city of Guarujá, São Paulo.

Description
The Guarujá Formation is 832 to 2500 m thick, and consists of oolitic calcarenites, which laterally grade to greyish ochre and brownish grey calcilutites and grey marls. These facies are interbedded with the alluvial clastics of the Florianópolis Formation. The Guarujá name is restricted to the lowest limestone intercalation, previously named Lower Guarujá by Ojeda and Ahranha in Pereira and Feijó (1994). The microfacies indicate a tidal flat to shallow lagoon and open carbonate platform depositional environment. The age based on planktonic foraminifera and pollen is Early Albian.

Petroleum geology
The formation is the second-most important post-salt reservoir rock of the Santos Basin, after the Itajaí-Açu Formation.