Guiana Shield

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 world's largest expanse of tropical forest in any Precambrian shield area overlies it.

The Guiana Shield underlies Guyana (previously British Guiana), Suriname (formerly 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 metavolcanic rocks (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. The region houses over 3000 vertebrate species: 1168 freshwater fish, 269 amphibians (54% endemics), 295 reptiles (29%), 1004 birds (7.7%), and 282 mammals (11%).

The diversity of invertebrates remains largely undocumented, but several species of endemic butterflies and dung beetles exist.

There are three upland areas of the Guiana Shield:

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

• The Tumucumaque Uplands 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 Ocean.

• 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 table 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.

Political map of the Guiana Shield

Guiana Highlands

The Guiana Highlands is a heavily forested plateau and low-mountain region of South America, located north of the Amazon River and south of the Orinoco River.

The Guiana Highlands 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 region covers the southern half of Venezuela, all of the Guianas except for the low Atlantic coastal plain, the northern part of Brazil and a portion of southeastern Colombia. It extends over 1,776,046 sq km (685,732 sq mi), including lowland areas.

From an area standpoint, approximately 50% of the region is in Brazil, 25% in Venezuela, 12% in Guyana, 8% in Suriname and 5% in French Guiana.

The region comprises the higher elevations of the Guiana Shield. It is perforated by a series of ancient uplands and highlands between 500 and 3,000 m (1,640 and 9,840 ft) in height. The tallest elevations comprise the Pantepui forests and shrublands ecoregion.

Plant life in the Guiana Highlands is rich, and over 13,000 species of vascular plants have been found, approximately 40% of which are considered endemic.

The Guianan rainforest is similar to the Amazon Rainforest, and known protected areas include:

• Iwokrama Forest, Guyana

• Kaieteur National Park, Guyana

• Kanuku Mountains Protected Area, Guyana

• Central Suriname Nature Reserve, Suriname

• Guiana Amazonian Park, French Guiana

• Tumucumaque Mountains National Park, Brazil

• Canaima National Park, Venezuela

• Parima-Tapirapeco, Venezuela

• Serranía de la Neblina, Venezuela