Guyana Shield

The Amazon basin comprises an area of about 6.4 millions km, extending between the Guyana Shield to the north and the Brazilian Shield to the south with the Andean and sub-Andean regions to the west. 

Sobolev N. V., Yefimova E. S., Channer D. M. D., Anderson P. F. N., and Barron K. M. (1998) Unusual upper mantle beneath Guaniamo, Guyana Shield, Venezuela evidence from diamond inclusions. Geology 26, 971-974. 

Edmond J. M., Palmer M. R., Measures C. 1., Grant B., and Stallard R. F. (1995) The fluvial geochemistry and denudation rate of the Guyana shield in Venezuela, Columbia and Brazil. Geochim. Cosmochim. Acta 59, 3301-3325. 

Allan K. Gibbs and Chri toi4i N. Barton The geology cftite Guyana Shield... 

Extensive, horizontal sandstone plateaus occur in tropical shield areas. Well-known examples are the Precambrian Roraima sandstone formations on the Guiana Shield and the Voltaian sandstone formations in Western Africa. Major occurrences of consolidated sands are found in Northern Africa, in Guyana and Surinam, eastern Peru, northeastern Brazil and in Liberia (western Africa). These sandstone formations have a history of tropical weathering in common they all have a deep weathering mantle of bleached, white sands that are very rich in quartz, poor in clay and excessively drained. Electrolyte contents differ by region In arid and semi-arid areas where evaporation exceeds precipitation, salts and carbonates may accumulate at or near the surface of the soil. 

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