6. Geological history of the Greater Amazonas Basin in Brazil

Abstract

This chapter discusses stratigraphy and sediment sequences, along with the depositional environments and basin history of Acre Basin, Solimoes Basin, Amazonas basin, and Amazon Mouth Basin. The westernmost Acre Basin, currently part of an Andean foreland basin, is separated from the Solimoes or Upper Amazonas Basin by the Iquitos arch. The Purus arch divides the Solimoes Basin and the Middle–Lower Amazonas Basin, actually called “simply Amazonas Basin.” The Gurupa arch divides this Amazonas Basin from the Amazon Mouth Basin that exists at the Atlantic coast. The Acre Basin is formed to the west of the Iquitos arch and extends into Peru and Equador as an Andean foreland basin. In Brazilian territory, it occupies a surface of about 230,000 km 2 in the westernmost parts of Acre and Amazonas States and is drained by the Javari and Jurua rivers with their affluents flowing into the Solimoes River, affluent of the Amazon. The Solimoes, formerly called “Upper Amazonas Basin” extends for about 40,000 km 2 in Amazonas State and is limited in the north by the Guyana shield and in the south by the Central Brazilian or Guapore shield. The Amazonas Basin, formerly known as the Middle and Lower Amazonas sub-basins, is a rather narrow trench that occupies a surface of approximately 500,000 km 2 , covering parts of Amazonas and Para States. It is limited in the north by the Guyana shield and in the south by the Central Brazilian shield.