Guiana Shield (South America)

Guiana Shield (South America)

Thu, 02/07/2019 - 20:46

The Guiana Shield is one of the three cratons of the South American Plate. It is a 1.7 billion-year-old Precambrian geological formation in northeast South America that forms a portion of the northern coast. The higher elevations on the shield are called the Guyanan Highlands.

The Guiana Shield is one of the three cratons of the South American Plate. It is a 1.7 billion-year-old Precambrian geological formation in northeast South America that forms a portion of the northern coast. The higher elevations on the shield are called the Guyanan Highlands, which is where the table-like mountains called tepuis are found and are also the source of some of the world's most spectacular waterfalls such as Angel Falls, Kaieteur Falls and Kuquenan Falls.

The Guiana Shield underlies Guyana (previously British Guiana), Suriname (previously Dutch Guiana) and French Guiana (or Guyane), much of southern Venezuela, as well as parts of Colombia, and Brazil.

The rocks of the Guiana Shield consist of metasediments and metavolcanics (greenstones) overlain by sub-horizontal layers of sandstones, quartzites, shales and conglomerates intruded by sills of younger mafic intrusives such as gabbros.

The Guiana Shield is one of the most biodiverse regions in the world, with many endemic species.

There are three upland areas of the Guiana Shield:

  • The Guiana Highlands (or Guyanan Highlands) proper are in Venezuela east of the Orinoco and extend across much of west-central Guyana and into the northern Roraima state in Brazil.

  • The Tumucumaque Uplands which are a series of central massifs in an arc from the Wilhelmina Mountains of south-central Suriname, along the southern boundary of Suriname and Guyana, forming the Acarai Mountains of Roraima state and the Tumuc-Humac Mountains of Pará and Amapá states of Brazil. From this arc, the southern uplands slope gently downwards towards the Amazon River and the northern uplands slope gently downwards toward the Atlantic.

  • The Chiribiquete Plateau is a sandstone topped plateau with an elevation of 900 m (2,953 ft) that forms the western edge of the shield. The plateau is separated from the eastern Andes by the thick Neogene sediments of the Sub-Andean Trough that runs along the northern and western rim of the Guiana Shield.