Geology of Brazil
 
Brazil is totally contained in the South American Platform, whose basement is of very complex geologic evolution, that originated in the Archean period. Brazil had its consolidation completed between the Proterozoic Superior period and the beginning of the Palaeozoic period, with the closing in the Brazilian cycle.
 
 
  Crystalline shields
  Sedimentary basins
 
 
The basement of the South American Platform is essentially structured on metamorphic rocks of amphibolite to granulite facies and granitoids of Archean age, associated with the Proterozoic units that are represented usually by folded strips of green schist facies and sedimentary and volcanic coverings, (seldom metamorphosed) and several granitoids.

That basement is widely exposed in great shields, separated from each other by fanerozoic coverings, whose limits extend to the neighboring countries. Prominent are the shields of Guyana, Central Brazil and Atlantic.

The shield of Guyana extends to the north of the basin of Amazonas. The shield of the Brazil-central, or Guaporé extends to the interior of Brazil and south of that basin, while the Atlantic shield is exposed in the oriental portion reaching the Atlantic border. These shields are exposed in more than 50% of the area of Brazil.

On that platform were developed in Brazil, in stable conditions of ortho-plataform, starting from Ordovician-Silurian, the sedimentary and volcanic coverings that filled spatially three extensive basins with sineclisis character: Amazonas, Paraíba and Paraná. Besides those basins, several other smaller basins, including coastal basins and other sedimentary areas, occur exposed on the platform.
 
Geomorphology
 
The relief of Brazil, in agreement with Aziz Ab'Saber's classification, it is divided in two great plateau areas and three plain areas as follows:

  • Plateau of Guyana, embracing the mountainous area and the Amazon North Plateau. Located in the extreme north of the country, it is an integral part of the shield of Guyana, presenting crystalline rocks of the Precambrian period. This area includes the highest elevation in Brazil - the Pico da Neblina, with an altitude of 3,014 m.
  • Brazilian plateau, subdivided in Central, Maranhão-Piauí, Northeastern Brazil, mountains and plateau of the East and Southeast, Southern and Uruguayan-Riograndense, it is formed by quite worn crystalline lands and sedimentary basins. It is located in the central part of the country, and encompasses great areas of the national territory.
  • Plains and amazon low lands. Located in the North region of the country, below the Plateau of Guyana, it presents three different altimetric levels - valleys, constituted by lands of recent formation near the margins of the rivers; fluvial terraces, with maximum altitudes of 30 m and periodically flooded; and low-plateaus, formed by lands of Tertiary.
  • Plain of the Pantanal, located in the area west of the state of Mato Grosso do Sul and Southwest of Mato Grosso, it is formed by lands of Quaternary.
  • Plains and coastal low lands, accompanying the Brazilian coast from Maranhão to the south of the country, it is formed by lands of the Tertiary and for current lands of Quaternary.
  • It should be noted that the Brazilian relief doesn't present formation of very high mountainous chains, prevailing altitudes are below 500 m, since it was developed on an old geologic base, without recent tectonic movements.
     

     
    The information given here was extracted of the site   Brazilian Environmental Mall
     
    Page created and designed by Marlon Machado
    Send comments to   marlon@brcactaceae.org 
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