Paleogeographic Development of South America

Abstract

The post-Proterozoic geologic history of South America was controlled by the distribution and interplay of certain major geotectonic units, classed in five groups, which form the structural framework of the continent: cratons (Guiana, Central Brazilian, and Coastal Brazilian shields), intercratonic basins (Amazonas, Parnaiba, Sao Francisco, and Parana), pericratonic basins (Llanos-Iquitos-Acre-Beni-Chaco-Pampas plains), nesocratons (Pampean Ranges, Patagonia, and Deseado massifs), and geosynclines (Andean belts). Since Early Cambrian time the cratonic and nesocratonic areas have maintained stable to substable positive tendencies, the intercratonic and pericratonic areas have shown vertical sub-stability to submobility with intermittent but decreasing subnegative tendencies, and the western geosynclinal belts have been highly mobile, deformable elements with recurrent negative tendencies, which have witnessed the main sedimentary-tecto-magmatic activity of the continent. The paleogeographic development of South America since Cambrian time is summarized in 46 maps arranged in 33 figures, covering different geological intervals. Marine, continental, and mixed or brackishwater facies are differentiated, and the main areas of volcanic and glacial accumulation are plotted. The explanatory text-essentially a list of the main areas of exposure of the different stratigraphic units--makes brief references to the main diastrophic, volcanic, and glacial episodes.