ABSTRACT

This chapter begins with the problems of central Amazonia and examines its northern and southern margins. In Brazil, the area called central Amazonia is the strip of land that stretches on each bank of the Amazon River from the Atlantic Ocean to the confluence of the Rio Negro with the Solimões. Central Amazonia is a tectonic trough, perhaps an old rift valley. Sedimentary rocks (limestones, sandstones, siltstones and slates) of Upper Cambrian to Carboniferous age have been deposited and affected by cover-folds. In western Amazonia, valley landforms are different although, between valleys, intensive dissection still prevails. In some regions, other evidence of semi-arid climates has been observed. Alluvial forms are quite different in western Amazonia from those described for central Amazonia. This results from the relative proximity of the Andes, which means that this region can be considered as a piedmont of the Andes.