Editing Guiana Shield

{{Short description|Precambrian geological formation in northeast South America}}
{{Infobox settlement
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[[File:Cerros de Mavecure (Guainía, Colombia).JPG|thumb|[[Cerros de Mavecure]], [[Guainía Department|Guainía department]], Colombia]]
[[File:Salto Angel - Cañon del Diablo.JPG|thumb|right|Devil's Canyon in the [[Canaima National Park]], Venezuela]]
[[File:Guyanas.svg|thumb|right|Map of the Guianas]]
The '''Guiana Shield'''<ref>The term  ''Guiana''  or ''The [[Guyanas|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.</ref> ({{langx|fr|Plateau des Guyanes, Bouclier guyanais}}; {{langx|nl|Hoogland van Guyana, Guianaschild}}; {{langx|pt|Planalto das Guianas, Escudo das Guianas}}; {{langx|es|Escudo guayanés}}) is one of the three [[craton]]s of the [[South American Plate]]. It is a 1.7 billion-year-old [[Precambrian]] geological [[Shield (geology)|formation]] in northeast [[South America]] that forms a portion of the northern coast.<ref>Hammond, David S. (ed.) (2005) ''Tropical Forests of the Guiana Shield'' CABI Publishing, Wallingford, UK, ISBN</ref> The higher elevations on the [[Shield (geology)|shield]] are called the '''Guiana Highlands''', which is where the table-like mountains called [[tepui]]s 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]].

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 ([[Greenschist|greenstones]]) overlain by sub-horizontal layers of [[sandstones]], [[quartzites]], [[shales]] and [[Conglomerate (geology)|conglomerates]] intruded by sills of younger mafic intrusives such as [[gabbro]]s.<ref>Gibbs, A.K. and Barron,C.N. (eds) (1993) ''The Geology of the Guiana Shield'' Oxford University Press, Oxford, UK, ISBN</ref>

== 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 (geology)|Fault]] marks the southern boundary of the complex. South of that fault are Early [[Proterozoic]] rocks consisting of the [[metavolcanic rock|metavolcanic]] Pastora [[geological unit|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 sediment]]ary rocks. These [[Precambrian]] sediments include quartz [[sandstones]], [[quartzite]]s, and [[conglomerate (geology)|conglomerates]] presumed to be 1.8 to 1.4 [[Giga annum|Ga]] in age.<ref>{{cite book|title=Geology and Mineral Resource Assessment of the Venezuelan Guayana Shield, USGS Bulletin 2062|date=1993|publisher=US Government Printing Office|pages=10–15}}</ref><ref>{{cite book|last1=Wray|first1=Robert|editor1-last=Migon|editor1-first=Piotr|title=The Gran Sabana: The World's Finest Quartzite Karst?, in Geomorphological Landscapes of the World|date=2010|publisher=Springer|isbn=9789048130542|pages=80–81}}</ref>

== Geomorphology ==
There are three upland areas of the Guiana Shield:
# 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.
# 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 {{convert|900|m|ft|0|abbr=on}} 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 [[tepui]]s, 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 {{convert|2995|m|ft}}.<ref name="ibge2016">{{cite press release |url=http://saladeimprensa.ibge.gov.br/noticias?view=noticia&id=1&busca=1&idnoticia=3109 |title=Geociências: IBGE revê as altitudes de site Pontos culminates |language=pt |trans-title=Geosciences: IBGE revises the altitude of seven high points | location=Brasília |publisher=[[Brazilian Institute of Geography and Statistics]] (IBGE) |date=2016-02-29 |access-date=2016-03-02 }}</ref> 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|date=August 2015}}

== Ecology ==
[[File:H chimantensis2.jpg|thumb|upright|''[[Heliamphora chimantensis]]'', [[endemism|endemic]] to the [[Chimantá Massif]] (a [[Venezuela]]n part of the Guiana Shield)]]
The Guiana Shield is one of the regions of highest [[biodiversity]] in the world, and has many [[endemism|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%).<ref>{{cite journal|last1= Hollowell|first1= T.|first2= R.P. |last2= Reynolds|year= 2005|title= Checklist of the Terrestrial Vertebrates of the Guiana Shield|journal= Bulletin of the Biological Society of Washington|volume= 13|url= http://botany.si.edu/bdg/pdf/bswa_13_all.pdf}}</ref><ref>{{cite journal| last1 = Stachowicz | first1 = Izabela| last2 = Ferrer Paris | first2 = José Rafael| last3 = Quiroga-Carmona | first3 = Marcial| last4 = Moran | first4 = Lisandro| last5 = Lozano | first5 = Cecilia| date       = 2020| title      =  Baseline for monitoring and habitat use of medium to large non-volant mammals in Gran Sabana, Venezuela| journal    =  Therya| volume     =  11| issue = 2| pages      =  169–179| doi        =  10.12933/therya-20-891| doi-access = free| hdl = 1959.4/unsworks_67008| hdl-access = free}}</ref><ref>{{cite journal|last1= Vari|first1= R.P.|first2= C.J.|last2= Ferraris Jr.|first3= A.|last3= Radosavljevic|first4= V.A.|last4= Funk|year= 2009|title= Checklist of the freshwater fishes of the Guiana Shield|journal= Bulletin of the Biological Society of Washington|volume= 17|url= http://botany.si.edu/bdg/pdf/bswa_fish-chcklst_2009-complete.pdf}}</ref> Diversity of invertebrates remains largely undocumented, but there are several species of endemic butterflies and dung beetles.<ref name="IndicativeResponse">{{cite journal|last1=Ferrer-Paris|first1=José R|last2=Lozano|first2=Cecilia|last3=Cardozo-Urdaneta|first3=Arlene|last4=Thomas Cabianca|first4=Arianna|title=Indicative response of ''Oxysternon festivum'' Linné (Coleoptera: Scarabaidae) to vegetation condition in the basin of the Orinoco river, Venezuela|journal=Journal of Insect Conservation|volume=20 |issue=3|pages=527–538|doi=10.1007/s10841-016-9886-6|year=2016|s2cid=17263106}}</ref><ref name="ViloriaPantepui">{{cite journal|last1=Costa|first1=Mauro|last2=Viloria|first2=Ángel L.|last3=Hubber|first3=Otto|last4=Attal|first4=Stéphane|last5=Orellana|first5=Andrés|title=Lepidoptera del Pantepui. Parte I: Endemismo y caracterización biogeográfica|journal=Entomotropica|date=2013|volume=28|issue=3|pages=193–217|url=http://www.entomotropica.org/index.php/entomotropica/article/view/414/449|access-date=25 June 2016|archive-url=https://web.archive.org/web/20160827045133/http://www.entomotropica.org/index.php/entomotropica/article/view/414/449|archive-date=27 August 2016|url-status=dead}}</ref>

Plant life is equally rich and 13,367 species of [[vascular plant]]s have been found, approximately 40% of which is considered endemic.<ref>{{cite journal|last1= Funk|first1= V.|first2= T.|last2= Hollowell|first3= P.|last3= Berry|first4= C.|last4= Kelloff|first5= S.N.|last5= Alexander|year= 2007|title=Checklist of the Plants of the Guiana Shield (Venezuela: Amazonas, Bolivar, Delta Amacuro; Guyana, Surinam, French Guiana)|journal= Contributions from the United States National Herbarium|volume= 55|url= http://botany.si.edu/bdg/pdf/vol55web.pdf}}</ref> The shield is overlain by the largest expanse of tropical forest on any Precambrian shield area in the world.<ref>Hammond, David S. (ed.) (2005) ''Tropical Forests of the Guiana Shield'' CABI Publishing, Wallingford, UK, ISBN</ref> Guianan rain forest is similar in nature to [[Amazon Rainforest|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 National Park|Canaima]], [[Parima Tapirapecó National Park|Parima-Tapirapeco]] and [[Serranía de la Neblina National Park|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]].<ref>{{Cite web | url=http://www.ramsar.org/es/complejo-de-humedales-de-la-estrella-fluvial-in%C3%ADrida-efi | title=Colombia &#124; Ramsar}}</ref>

According to recent researches, although ecosystems of the Guayana Highlands remain vibrant, emerging issues (including "a well-known [[Invasive species|invasive]] plant elsewhere" ''[[Poa annua]]'' and "one of the most aggressive weeds" ''[[Polypogon elongatus]]'') and infectious faecal bacteria ''[[Helicobacter pylori]]'' have been documented.<ref>{{cite journal |last1= Rull|first1= V.|last2= Vegas-Vilarrúbia|first2= T.|last3= Safont|first3= E.|date= 2016|title= The Lost World's pristinity at risk|journal= [[Diversity and Distributions]]|volume= 22|issue= 10|pages= 995–999|doi= 10.1111/ddi.12469|bibcode= 2016DivDi..22..995R|url= https://digital.csic.es/bitstream/10261/137349/3/Rull_Diversity_and_Distributions_22_995_postprint.pdf|hdl= 10261/137349|s2cid= 23002053|hdl-access= free}}
</ref>

== See also ==
*{{annotated link|Gran Sabana}}
*{{annotated link|Tepui}}
*{{annotated link|Canadian Shield}}
*{{annotated link|Caribbean South America}}
*{{annotated link|Mount Roraima}}
*{{annotated link|Pico da Neblina}}
*{{annotated link|Great American Interchange}}
*{{annotated link|Geography of South America}}

== References ==
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{{reflist}}

== External links ==
* {{Commons category-inline|Guiana Shield}}
* {{Commons-inline|Guiana Highlands}}
* {{Commons category-inline|Tepuis}}

{{Clear}}

{{Major South American geological formations}}
{{Physiographic regions}}
{{Tepuis|state=collapsed}}
{{Geographical Regions of Venezuela}}
{{Authority control}}

[[Category:Shields (geology)]]
[[Category:Guayana Highlands|.]]
[[Category:The Guianas|Shield]]
[[Category:Plateaus of South America]]
[[Category:Plateaus of Brazil]]
[[Category:Plateaus of Venezuela]]
[[Category:Geographical regions of Venezuela]]
[[Category:Geography of Colombia]]
[[Category:Geography of French Guiana]]
[[Category:Geography of Guyana]]
[[Category:Geography of Suriname]]
[[Category:Natural regions of South America]]
[[Category:Geology of South America]]
[[Category:Geology of Brazil]]
[[Category:Geology of Colombia]]
[[Category:Geology of French Guiana]]
[[Category:Geology of Guyana]]
[[Category:Geology of Suriname]]
[[Category:Geology of Venezuela]]
[[Category:Flora of northern South America|.]]
[[Category:Natural history of South America]]
[[Category:North Region, Brazil]]
[[Category:Geography of Amapá]]
[[Category:Geography of Pará]]
[[Category:Geography of Roraima]]
[[Category:Precambrian South America]]