Amazonian Shield

geology

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June 17, 2026

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The Amazonian Shield is a large, stable area of the Earth's crust in South America, primarily composed of Precambrian crystalline rocks that are over 540 million years old. It is considered a continental nucleus, with younger rock belts often bordering it. This shield occupies a significant portion of the eastern part of the continent.1

The Amazon basin itself is a large depression situated between the Guiana Highlands to the north and the Brazilian Highlands to the south. During the Pliocene Epoch, this area was covered by a vast freshwater sea. Later, during the Pleistocene Epoch, an outlet to the Atlantic Ocean formed, leading to the river system becoming entrenched in the former seafloor. The modern Amazon River and its tributaries flow through a system of drowned valleys filled with alluvium.2

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continental shield
…shield area is called the Amazonian Shield. It occupies much of the eastern bulge of the continent. Smaller areas of Precambrian rocks to the north and south of the Amazonian Shield are designated the Guiana and Platian shields, respectively.
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…shield area is called the Amazonian Shield. It occupies much of the eastern bulge of the continent. Smaller areas of Precambrian rocks to the north and south of the Amazonian Shield are designated the Guiana and Platian shields, respectively.
Read More