Orinoco basin

Fig. 9-3 Conceptual model to describe the interaction between chemical weathering of bedrock and down-slope transport of solid erosion products. It is assumed that chemical weathering is required to generate loose solid erosion products of the bedrock. Solid curve portrays a hypothetical relationship between soil thickness and rate of chemical weathering of bedrock. Dotted lines correspond to different potential transport capacities. Low potential transport capacity is expected on a flat terrain, whereas high transport is expected on steep terrain. For moderate capacity, C and F are equilibrium points. (Modified with permission from R. F. Stallard, River chemistry, geology, geomorphology, and soils in the Amazon and Orinoco basins. In J. I. Drever, ed. (1985), "The Chemistry of Weathering," D. Reidel Publishing Co., Dordrecht, The Netherlands.)...

Stallard, R. F. (1985). River chemistry, geology, geomorphology, and soils in the Amazon and Orinoco basins. In "The Chemistry of Weathering" (J. I. Drever, ed.), pp. 293-316. D. Reidel Publishing Co., Dordrecht, Holland, NATO ASI Series C Mathematical and Physical Sciences 149. 

The earliest available preparations, made as infusions and concentrated to a syrup by the native people, were designated as calabash (gourd), tubo- (bamboo), or pot (clay pot) curare depending upon the containers in which the drug was packaged. Curare is obtained from the upper regions of the Amazon river, the Orinoco basin, and the eastern slopes of the Ecuadorian plateau. The term curare is derived from the Indian name (woorari, urari) for poison (Grollman, 1962). 

Material Lower parts of stem from vine found in Amazone and Orinoco basins of South America. 

Jaffe, R., Wolff, GA., Cabrera, A.C., and Carvajal-Chitty, H. (1995) The biogeochemistry of lipids in rivers from the Orinoco basin. Geochim. Cosmochim. Acta 59, 4507 1522. 

Calabash curare originates in the more northern parts of the subcontinent, particularly in the Amazon and Orinoco basins and surrounding regions. It is considerably more toxic than tube-curare and has presented much more formidable chemical problems with regard to both isolation and structural elucidation. 

The comparison of REE concentrations for the <0.2 pm fraction with the lower-filter-size fraction shows that there is no unique pattern of colloidal material when rivers of different pH and different environments are compared. Ultrafiltration experiments conducted by Deberdt et al. (2002) on rivers from the Amazon and Orinoco basins as well as on Cameroon Rivers show slightly depleted LREE patterns to flat REE patterns when the colloidal fraction is normalized to the bulk solution. The results obtained by Sholkovitz (1995) and Ingri et al. (2000) for rivers... 

The tree is said to have been discovered in the Amazon or Orinoco basin at least 4000 years ago. Christopher Columbus was the first European to encounter the beans, during his fourth voyage to the New World in 1502, but he virtually ignored them. It was two decades later that the Spanish conquistador Hernando Cortes helped spread the valuable cocoa bean crop to the Caribbean and Africa, and then he introduced drinking chocolate into Spain in 1528. The cacao tree is now cultivated in West Africa, South America, Central America, and the Far East. At world level, the demand for cocoa is generally measured by reference to world grindings. The world grindings of cocoa beans in 2003/2004 approached three million metric tons. 

Figure 1. Vertical distribution of principal vegetation belts in the cordillera de Merida, a tropical high range in the northern Andes of Venezuela. The selected transect extends 120 km in the northerly direction across two parallel ranges of different elevation. Vegetation bands appear slanted towards the outer flanks because of greater moisture levels carried by easterly trade winds from the Orinoco basin and northeasterly winds from the Caribbean Sea and the Maracaibo lake basin to the north.

Virtually nothing is known about cloud or fog contributions to soil geochemistry in tropical and subtropical mountains and it would be desirable to better understand the various contributors to nutrient inputs, especially considering the importance of frequent fire cycles in lowlands upwind from high elevation ranges such as the Amazon and Orinoco basins and the Andean barrier. 

Dissolved solid concentrations (dissolved phases derived from the weathering of bedrock) can be used to estimate ranges of denudation rates for particular regions. Histograms of dissolved solid concentrations for different morphotectonic regions of the Amazon and Orinoco basins are presented in Fig. 

Jaffe R, Wolff GA, Cabrera AC, Chitty HC (1995) The biogeochemistry of lipids in river of the Orinoco Basin. Geochim Cosmochim Acta 59, 4507-4522. 

Aqueous extracts of S. toxifera and other various species of Strychnos plants indigenous to the Amazon-Orinoco basins are called curare (calabash curare) and are used by natives for hunting (105) (Sect. S.2.2.5.2). 

The region throughout which curare has been used is a wide, more or less semicircular, zone stretching from French Guiana to the Mato Grosso and covering the northern and western parts of the Amazon basin, the middle and upper parts of the Orinoco basin, the Montana of Ecuador and Peru, and northeastern Bolivia and adjacent parts of the central Brazilian plateau... 

S. rondeletioides Spruce ex Benth. is common in high forest on terra firme, where it grows as a huge bush-rope up to 50 m long, and on the shores of creeks, where it becomes a much smaller plant. It is widely distributed throughout the Amazon basin in Colombia, Venezuela, Brazil, Peru, and Bolivia it is also known to occur in the Orinoco basin (108, 217, 220). Specimens documenting its incorporation into curare originate from Colombia, Venezuela, and Brazil. 

JO Kaplan, The Piaroa. A People of the Orinoco Basin, Clarendon Press, Oxford, 1975, p. 38. 

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