The basin is bound by the Florianópolis High, separating it from the Santos Basin in the north and the Polônio High in the south, forming the border with the Punta del Este Basin. The coastal ranges Serras de Sudeste in Brazil and Cuchilla Grande in Uruguay form the western boundary, underlain by the Sierra Ballena Shear Zone. The onshore part of the basin is from north to south crossed by the Urussanga, Araranguá, Mampituba, Jacuí, Guaíba, Camaquã, Jaguarão/Yaguarón and Cebollatí Rivers.