is an area of highlands along the border between Brazil and Venezuela and Guyana.The southern Amazonian highlands cross parts of Rondonia and Mato Grosso and the southern parts of Amazonas and Para.

The Amazon basin is crossed by ridges or "paleoarches" that connect the Guiana and Central Brazil shields and divide it into geological sub-basins.They are the Iquitos or Jutai Arch in Peru and Acre, the Carauari