Sierra de Lema


The Sierra de Lema is an upland mountain range area with tepuis, located in Bolívar state of southeastern Venezuela.
The names Sierra Rinocote and Sierra Usupamo have historically been applied to its eastern and western portions, respectively.

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. It is partly within the bounds of Canaima National Park and encompasses a number of prominent tepuis, including the entire Los Testigos chain and Ptari Massif. The elevational range of the Sierra de Lema is around above sea level.
The chain of tepui mountains that comprises the Sierra de Lema is around wide. 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. When considering only the uplands that mark the northern boundary of the Gran Sabana, the Sierra de Lema spans around.
The extent of the range exceeds 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 in the west, very close to the confluence of the Paragua River and Caroní River.
'', 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. It is characterised by nutrient poor soils with a low pH and high aluminium content.
The El Mirador area at the base of the Sierra de Lema exhibits unusually high levels of the radioisotope Caesium-137, in both its soils and vegetation. This is likely related to the ground composition and cloud forest conditions of the site. The undulating, forested landscape of La Escalera also forms part of the Sierra de Lema.

Geology

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