[3] The vein of the Javaés forms a broad inland where it pours back into the main Araguaia, a 100,000 hectare expanse of igapós or flooded forest, blackwater river channels, and oxbow lakes called Cantão, protected by the Cantão State Park.A large portion of the Araguaia's course is navigable all year, but the river below the Cantão wetlands is interrupted by rapids.Its principal tributary is the Rio das Mortes, which rises in the Serra de São Jerônimo, near Cuiabá, Mato Grosso, and is navigable to Pará.Other important tributaries include the Bonito, Garcas, Tapirape and the Formoso or Cristalino on the west, and the Pitombas, Claro, Vermelho, Tucupa and Chavante on the east.[6] From 1972 to 1974 this region was the scene of a conflict between left-wing guerrilla movements and forces supporting the then military dictatorship.