Guiana Shield

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Guiana Shield
Map of the Guiana shield.png
Political map of the Guiana Shield
Coordinates: 5°08′36″N60°45′45″W / 5.14333°N 60.76250°W / 5.14333; -60.76250 Coordinates: 5°08′36″N60°45′45″W / 5.14333°N 60.76250°W / 5.14333; -60.76250
Region South America
Cerros de Mavecure, Guainia department, Colombia Cerros de Mavecure (Guainia, Colombia).JPG
Cerros de Mavecure, Guainía department, Colombia
Devil's Canyon in the Canaima National Park, Venezuela Salto Angel - Canon del Diablo.JPG
Devil's Canyon in the Canaima National Park, Venezuela
Map of the Guianas Guyanas.svg
Map of the Guianas

The Guiana Shield [1] (French : Plateau des Guyanes, Bouclier guyanais; Dutch : Hoogland van Guyana, Guianaschild; Portuguese : Planalto das Guianas, Escudo das Guianas; Spanish : Escudo guayanés) 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. [2] The higher elevations on the shield are called the Guiana Highlands, which is where the table-like mountains called tepuis are found. The Guiana Highlands are also the source of some of the world's most well-known waterfalls such as Angel Falls, Kaieteur Falls and Cuquenan Falls.

Contents

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. [3]

Geology

The oldest rocks in the shield consist of Archean Imataca Complex, composed of a quartz-feldspar gneiss and subordinate mafic gneiss. The Guri Fault marks the southern boundary of the complex. South of that fault are Early Proterozoic rocks consisting of the metavolcanic Pastora Supergroup and the granitic plutonic Supamo Complex. The Cuchivero Group consists of ash flow tuff and granitic plutonic rocks. The Early to Middle Proterozoic Roraima Group consists of continental clastic sedimentary rocks. These Precambrian sediments include quartz sandstones, quartzites, and conglomerates presumed to be 1.8 to 1.4 Ga in age. [4] [5]

Geomorphology

There are three upland areas of the Guiana Shield:

  1. The Guiana 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.
  2. 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.
  3. 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.

The north-central part of the Guiana Highlands is dominated by high flat-topped peaks called tepuis, of the Roraima supergroup and Quasi-Roraima formation, and the rounded granite peaks of the Parguaza and Imataca complexes to the north and southwestern edges of the area. The highest point in the shield is Pico da Neblina in Brazil at 2,995 metres (9,826 ft). [6] Pico da Neblina is the highest summit of the larger Neblina massif, a highly eroded sandstone plateau that straddles the Venezuela-Brazil border and that has lost the typical tabletop shape of the other tepuis in the region.[ citation needed ]

Ecology

Heliamphora chimantensis, endemic to the Chimanta Massif (a Venezuelan part of the Guiana Shield) H chimantensis2.jpg
Heliamphora chimantensis , endemic to the Chimantá Massif (a Venezuelan part of the Guiana Shield)

The Guiana Shield is one of the regions of highest biodiversity in the world, and has many endemic species. The region houses over 3000 vertebrate species: 1168 fresh water fish, 269 amphibians (54% endemics), 295 reptiles (29%), 1004 birds (7.7%), and 282 mammals (11%). [7] [8] [9] Diversity of invertebrates remains largely undocumented, but there are several species of endemic butterflies and dung beetles. [10] [11]

Plant life is equally rich and 13,367 species of vascular plants have been found, approximately 40% of which is considered endemic. [12] The shield is overlain by the largest expanse of tropical forest on any Precambrian shield area in the world. [13] Guianan rain forest is similar in nature to Amazonian rain forest and known protected areas include the Iwokrama Forest of central Guyana, Kaieteur, Kanuku National Park of southern Guyana, the UNESCO World Heritage Site Central Suriname Nature Reserve of Suriname, the Guiana Amazonian Park in French Guiana and the Tumucumaque National Park in the Amapá State of Brazil. In Venezuela the forests are protected by Canaima, Parima-Tapirapeco and Serranía de la Neblina national parks. In 2014, the Government of Colombia designated a 250 hectare area of the Guiana Shield, as a Ramsar Wetland, thus becoming a protected area of international importance in accordance to the Ramsar Convention. [14]

According to recent researches, although ecosystems of the Guayana Highlands remain vibrant, emerging issues (including "a well-known invasive plant elsewhere" Poa annua and "one of the most aggressive weeds" Polypogon elongatus ) and infectious faecal bacteria Helicobacter pylori have been documented. [15]

See also

Related Research Articles

Tepui Table-top mountain or mesa in the Guiana Highlands of South America

A tepui, or tepuy, is a table-top mountain or mesa found in South America, especially in Venezuela and western Guyana. The word tepui means "house of the gods" in the native tongue of the Pemon, the indigenous people who inhabit the Gran Sabana.

Mount Roraima is the highest of the Pakaraima chain of tepuis or plateaux in South America. It is located at the junction of Venezuela, Brazil and Guyana. A characteristic large flat-topped mountain surrounded by cliffs 400 to 1,000 meters high. The highest point of Mount Roraima is located on the southern edge of the cliff at an altitude of 2,810 meters in Venezuela, and another protrusion at an altitude of 2,772 meters at the junction of the three countries in the north of the plateau is the highest point in Guyana. The name of Mount Roraima came from the native Pemon people. Roroi in the Pemon language means "blue-green", and ma means "great".

Pico da Neblina Highest mountain in Brazil

Pico da Neblina is the highest peak in Brazil, 2,995.3 metres (9,827 ft) above sea level, in the Serra da Neblina, part of the Serra do Imeri, a section of the Guiana Highlands on the Brazil-Venezuela border. As determined by a border survey expedition in 1962, its summit lies just within Brazilian territory, at a horizontal distance of only 687 m (2,254 ft) from the Venezuelan border at Pico 31 de Março.

<span class="mw-page-title-main">Canaima National Park</span> National park in Venezuela

Canaima National Park is a 30,000 km2 (12,000 sq mi) park in south-eastern Venezuela that roughly occupies the same area as the Gran Sabana region. It is located in Bolívar State, reaching the borders with Brazil and Guyana.

La Gran Sabana is a region in southeastern Venezuela, part of the Guianan savanna ecoregion.

Mazaruni River

The Mazaruni River is a tributary of the Essequibo River in northern Guyana. Its source is in the remote western forests of the Pakaraima Mountains and its confluence with the Cuyuni River is near Bartica. As it descends from the Guiana Highlands the river runs south-east, past Issano, then northward to Bartica. The river is a source of alluvial gold.

The Pacaraima or Pakaraima Mountains are a mountain range primarily in southwestern Guyana, and into northern Brazil and eastern Venezuela.

Pico da Neblina National Park

Pico da Neblina National Park is a national park in the state of Amazonas in the north of Brazil, bordering on Venezuela. It overlaps with several indigenous territories, which creates tensions over land use, as does the military presence due to the border location. The park includes lowlands around the Rio Negro, partly flooded, and mountains that include the highest peak in Brazil, after which the park is named. The wide variety of physical environments supports great biodiversity, including several endangered species.

Mount Ayanganna is a sandstone tepui in the Pakaraima Mountains of western Guyana, and located 85 kilometres (53 mi) east of Mount Roraima.

Guayana Region, Venezuela Administrative region of eastern Venezuela

The Guayana Region is an administrative region of eastern Venezuela.

Cerro Sarisariñama is a tepui, a flat-topped mountain in Jaua-Sarisariñama National Park at the far south-west of Bolívar State, Venezuela, near the border with Brazil. Its altitude range is between 300 m (980 ft) and 2,350 m (7,710 ft). The name of the mountain originates from the tale of local Ye'kuana Indians about an evil spirit living in caves up in the mountain and devouring human flesh with a sound "Sari... sari...".

Pico 31 de Março Mountain on the Brazil-Venezuela border

Pico 31 de Março, or Pico Trinta e Um de Março in full, also known as Pico Phelps, is a mountain on the Brazil–Venezuela border. At 2,974 metres (9,757 ft) above sea level, it is Brazil's second highest mountain. It is part of the Neblina massif, and the latter's summit Pico da Neblina, Brazil's highest summit, is only 687 m (2,254 ft) away. Pico 31 de Março can be considered a secondary summit of Pico da Neblina. Therefore, it is usually climbed by expeditions primarily aiming to reach the other peak. The two are linked by a col that can be easily traversed in a short trek of about an hour.

Tumuk Humak Mountains

The Tumuk Humak Mountains are a mountain range in South America, stretching about 120 kilometers (75 mi) east–west in the border area between Brazil in the south and Suriname and French Guiana in the north. In the language of the Apalam and Wayana peoples, Tumucumaque means "the mountain rock symbolizing the struggle between the shaman and the spirits". The range is very remote and almost inaccessible.

Distribution of <i>Heliamphora</i>

The natural range of the carnivorous plant genus Heliamphora is restricted to the southern Venezuelan states of Amazonas and Bolívar, and to adjacent portions of northern Brazil and western Guyana, an area corresponding to the western part of the Guayana Shield. These plants are largely confined to the summits and foothills of the sandstone table-top mountains of the region, known as tepuis.

Wei-Assipu-tepui

Wei-Assipu-tepui, also known as Little Roraima or Roraimita, is a minor tepui of the Eastern Tepuis chain. It lies just off the northeastern flank of Roraima-tepui, directly on the border between Brazil and the disputed Guayana Esequiba territory, claimed by Venezuela but controlled by Guyana, and very close to the tripoint of all three countries. The mountain is known for its extensive cave systems, with one extending for over a kilometre.

Guayana natural region Geographic region of Venezuela

The Guayana natural region also simply known as Guayana in Venezuela, is a large massif of approximately 441,726 km2 (170,551 sq mi) area, equivalent to 48.2% of the total continental territory of the country.

Guianan savanna

The Guianan savanna (NT0707) is an ecoregion in the south of Venezuela, Guyana and Suriname and the north of Brazil. It is in the Amazon biome. The savanna covers an area of rolling upland plains on the Guiana Shield between the Amazon and Orinoco basins. It includes forested areas, but these are shrinking steadily due to the effect of frequent fires, either accidental or deliberate. The ecoregion includes the Gran Sabana region of Venezuela.

Guianan Highlands moist forests Type of plant habitat

The Guayanan Highlands moist forests (NT0124) is an ecoregion in the south of Venezuela and the north of Brazil and in Guyana, Suriname, French Guiana. It is in the Amazon biome. It encompasses an upland region with diverse fauna and flora, which contains dramatic tepuis, or sandstone table mountains. The region has been inaccessible in the past and is generally fairly intact, apart from the north and northeast where large scale agriculture, ranching and mining operations are steadily encroaching on the ecosystem. New roads are opening the interior to logging, and planned dams will have a drastic impact on the riparian zones.

Guianan moist forests

The Guianan moist forests (NT0125) is an ecoregion in the east of Venezuela, north of Brazil and the Guyanas. It is in the Amazon biome. The climate is hot and humid, with two rainy seasons each year. As of 1996 the tropical rainforest habitat was relatively intact, although there were mounting threats from illegal logging and gold mining.

The geology of Venezuela includes ancient Precambrian igneous and metamorphic basement rocks, layered with sedimentary rocks from the Paleozoic and Mesozoic and thick geologically recent Cenozoic sediments with extensive oil and gas.

References

  1. ↑ The term Guiana or The Guianas is often used as a collective name for Guyana, Suriname and French Guiana, and sometimes even includes the portions of Colombia, Venezuela and Brazil (including most of the state of Roraima) which are on the Guiana Shield.
  2. ↑ Hammond, David S. (ed.) (2005) Tropical Forests of the Guiana Shield CABI Publishing, Wallingford, UK, ISBN
  3. ↑ Gibbs, A.K. and Barron,C.N. (eds) (1993) The Geology of the Guiana Shield Oxford University Press, Oxford, UK, ISBN
  4. ↑ Geology and Mineral Resource Assessment of the Venezuelan Guayana Shield, USGS Bulletin 2062. US Government Printing Office. 1993. pp. 10–15.
  5. ↑ Wray, Robert (2010). Migon, Piotr (ed.). The Gran Sabana: The World's Finest Quartzite Karst?, in Geomorphological Landscapes of the World. Springer. pp. 80–81. ISBN   9789048130542.
  6. ↑ "Geociências: IBGE revê as altitudes de site Pontos culminates" [Geosciences: IBGE revises the altitude of seven high points] (Press release) (in Portuguese). Brasília: Brazilian Institute of Geography and Statistics (IBGE). 2016-02-29. Retrieved 2016-03-02.
  7. ↑ Hollowell, T.; Reynolds, R.P. (2005). "Checklist of the Terrestrial Vertebrates of the Guiana Shield" (PDF). Bulletin of the Biological Society of Washington. 13.
  8. ↑ Stachowicz, Izabela; Ferrer Paris, José Rafael; Quiroga-Carmona, Marcial; Moran, Lisandro; Lozano, Cecilia (2020). "Baseline for monitoring and habitat use of medium to large non-volant mammals in Gran Sabana, Venezuela". Therya. 11 (2): 169–179. doi: 10.12933/therya-20-891 .
  9. ↑ Vari, R.P.; Ferraris Jr., C.J.; Radosavljevic, A.; Funk, V.A. (2009). "Checklist of the freshwater fishes of the Guiana Shield" (PDF). Bulletin of the Biological Society of Washington. 17.
  10. ↑ Ferrer-Paris, José R; Lozano, Cecilia; Cardozo-Urdaneta, Arlene; Thomas Cabianca, Arianna (2016). "Indicative response of Oxysternon festivum Linné (Coleoptera: Scarabaidae) to vegetation condition in the basin of the Orinoco river, Venezuela". Journal of Insect Conservation. 20 (3): 527–538. doi:10.1007/s10841-016-9886-6. S2CID   17263106.
  11. ↑ Costa, Mauro; Viloria, Ángel L.; Hubber, Otto; Attal, Stéphane; Orellana, Andrés (2013). "Lepidoptera del Pantepui. Parte I: Endemismo y caracterización biogeográfica". Entomotropica. 28 (3): 193–217. Archived from the original on 27 August 2016. Retrieved 25 June 2016.
  12. ↑ Funk, V.; Hollowell, T.; Berry, P.; Kelloff, C.; Alexander, S.N. (2007). "Checklist of the Plants of the Guiana Shield (Venezuela: Amazonas, Bolivar, Delta Amacuro; Guyana, Surinam, French Guiana)" (PDF). Contributions from the United States National Herbarium. 55.
  13. ↑ Hammond, David S. (ed.) (2005) Tropical Forests of the Guiana Shield CABI Publishing, Wallingford, UK, ISBN
  14. ↑ "Colombia | Ramsar".
  15. ↑ Rull, V.; Vegas-Vilarrúbia, T.; Safont, E. (2016). "The Lost World's pristinity at risk" (PDF). Diversity and Distributions . 22 (10): 995–999. doi:10.1111/ddi.12469. hdl: 10261/137349 . S2CID   23002053.
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