The Amazon Basin is a large

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subside ...

(620,000 square kilometres (240,000 sq mi)) located near the middle and lower course of the Amazon River, south the Guiana Shield and north of the Central Brazilian Shield. The basin developed on a

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

that originated about 550 million years ago during the Cambrian.

Location

The Amazon Basin is located south of the Guiana Shield, north of the Central Brazilian Shield, east of the Solimões Basin, and west of the

Marajó Marajó () is a large coastal island in the state of Pará, Brazil. It is the main and largest of the islands in the Marajó Archipelago. Marajó Island is separated from the mainland by Marajó Bay, Pará River, smaller rivers (especially ...

Basin. It is bound to the west by the Púrus Arch and in the east by the Gurupá Arch. The basin has an elongated shape with a WSW-ENE orientation. Its long axis runs from the vicinity of Manaus to the area near the confluence of

Xingu River The Xingu River ( ; pt, Rio Xingu, ; Mẽbêngôkre: ''Byti'', ) is a river in north Brazil. It is a southeast tributary of the Amazon River and one of the largest clearwater rivers in the Amazon basin, accounting for about 5% of its water. ...

with the Amazon River.

Evolution of the Basin

The Amazon Basin was developed on a

, called the Sub-Amazonal Rift, that originated about 550 million years ago during continental collision of the

West African Craton The West African Craton (WAC) is one of the five cratons of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania Craton.Jessell M.W., Liégeo ...

. Parts of the rift were reactivated during the opening of the

South Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

. The Amazon Basin evolved through

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

activity including continental collision, subduction, and distortion of parts of the Andes Mountain Range.

Bauxite Deposits

The Amazon basin hosts large deposits of the aluminum-rich

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO ...

. The discovery of bauxite deposits approximately 70 years ago made Brazil one of the most important countries in terms of both production and possession of bauxite deposits.

References

Geology of Brazil Sedimentary basins of Brazil Paleozoic rifts and grabens {{Geology-stub