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The Sierra de Lema is an upland mountain range area with tepuis, located in Bolívar state of southeastern Venezuela.[1]

Sierra de Lema
Location in Venezuela,
with the Cuyuni River on the north and the Caroní River on the south & west.
Highest point
Elevation1,650 m (5,410 ft)[1]
Geography
LocationBolívar state,
Venezuela
Range coordinates06°N 62°W
Parent rangeGuayana Shield
Geology
Orogenyigneous, metamorphic, & sedimentary rock
Age of rockPrecambrian,
Mesozoic

The names Sierra Rinocote and Sierra Usupamo have historically been applied to its eastern and western portions, respectively.[2]


Geography


The Sierra de Lema is geologically part of the Guayana Shield, and biogeographically part of the Guayana Highlands.

Lying north of the Gran Sabana, it marks the drainage divide between the Caroní River and Cuyuni River drainage basins.[2] It is partly within the bounds of Canaima National Park[3] and encompasses a number of prominent tepuis, including the entire Los Testigos chain and Ptari Massif.[1][2] The elevational range of the Sierra de Lema is around 150–1,650 metres (490–5,410 ft) above sea level.[1][4]

The chain of tepui mountains that comprises the Sierra de Lema is around 30 kilometres (19 mi) wide.[2] Because the toponymy of the region remains largely unresolved, the stated length of the Sierra de Lema can vary widely, depending on the definition used.[1][2] When considering only the uplands that mark the northern boundary of the Gran Sabana, the Sierra de Lema spans around 80 km (50 mi).

The extent of the range exceeds 200 km (120 mi) if the entire chain separating the Caroní and Cuyuni drainage basins is included. By the latter definition, the Sierra de Lema stretches from Cerro Venamo in the east to Serranía Supamo and Cerro Santa Rosa (mountain) in the west, very close to the confluence of the Paragua River and Caroní River.[2]

Catopsis berteroniana, an epiphyte plant in the Sierra de Lema.
Catopsis berteroniana, an epiphyte plant in the Sierra de Lema.

Ecology


The old-growth forest section of the Sierra de Lema, in the Guayanan Highlands moist forests ecoregion, remains virtually intact. It covers a contiguous area of some 1,000 square kilometres (390 sq mi).[4] It is characterised by nutrient poor soils with a low pH and high aluminium content.[5]

The El Mirador ("The Lookout") area at the base of the Sierra de Lema exhibits unusually high levels of the radioisotope Caesium-137, in both its soils and vegetation.[6][7] This is likely related to the ground composition and cloud forest conditions of the site.[7] The undulating, forested landscape of La Escalera ("The Staircase") also forms part of the Sierra de Lema.[4][8]


Geology


The Sierra de Lema consists of an igneous-metamorphic basement overlain by Precambrian sedimentary rocks of the Roraima Group, with Mesozoic diabase intrusions.[1][4]


See also



References


  1. Huber, O. (1995). Geographical and physical features. In: P.E. Berry, B.K. Holst & K. Yatskievych (eds.) Flora of the Venezuelan Guayana. Volume 1. Introduction. Missouri Botanical Garden Press, St. Louis. pp. 1–61.
  2. (in Spanish) Brewer-Carías, C. (2012). La Sierra de Lema: una bisagra de vida. Río Verde 7: 73–86.
  3. (in Spanish) Torres, I.N. & D.D. Martín (November 2007). "Informe Final de la Evaluación del Parque Nacional Canaima, Venezuela, como Sitio de Patrimonio Natural de la Humanidad" (PDF). Mejorando Nuestra Herencia.
  4. Durán Rangel, C., A. Reif & L. Hernández (April 2011). Understanding small-scale disturbances in Guayana's montane forests: gap characterization in the Sierra de Lema, Venezuela. Interciencia 36(4): 272–280.
  5. Durán Rangel, C. (July 2011). Forest gaps structure and tree regeneration in a montane Guayanan forest, Sierra de Lema, Venezuela. Doctor of Science thesis, Albert-Ludwigs Universität, Freiburg im Breisgau.
  6. LaBrecque, J.J. & P.R. Cordoves (June 2005). Cesium-137 spatial activity in surface soils near and surrounding the Gurí Reservoir (Venezuela). Journal of Radioanalytical and Nuclear Chemistry 265(1): 91–94. doi:10.1007/s10967-005-0792-8
  7. LaBrecque, J.J., J.A. Alfonso & P.R. Cordoves (August 2008). Anomalously high activities of 137Cs in soils and vegetation on and near a diabase outcrop in La Sierra de Lema, Venezuela. Journal of Radioanalytical and Nuclear Chemistry 277(2): 405–411. doi:10.1007/s10967-007-7064-8
  8. Hernández, L., N. Dezzeo, E. Sanoja, L. Salazar & H. Castellanos (March 2012). Changes in structure and composition of evergreen forests on an altitudinal gradient in the Venezuelan Guayana Shield. Revista de Biología Tropical 60(1): 11–33.

Further reading







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