The formation crops out in and around the city of Curitiba and comprises mudstones and sandstones deposited in a fluvial floodplain environment.

The geologists named the formation after Guabirotuba [pt], a neighborhood of Curitiba, the capital of Paraná State.

[1] The formation is the lowermost sedimentary unit in the 3,000 square kilometres (1,200 sq mi) Curitiba Basin, a Cenozoic continental rift basin of southeastern Brazil,[2] overlying Cambrian basement comprising gneisses, amphibolites and migmatites of the Atuba Complex and metasediments of the Açungui Group.

[3][4] The 60 to 80 metres (200 to 260 ft) thick Guabirotuba Formation comprises a basal conglomerate,[5] mudstones and sandstones,[3] deposited in a fluvial floodplain environment.

[7] Heavy mineral analysis on the very abundant zircons, abundant epidote, common tourmaline and kyanite and rare rutile has provided insight in the paleocurrents of the fluvial environment, with predominant flow directions towards the northwest and east-northeast.