Abstract
The southeastern part of the Amazonian Craton is made up of Archean and Lower Proterozoic sequences including gneiss, greenstone belts and a huge granitic suite. During the Middle Proterozoic this craton was affected by an extensional regime, during which fault zones of the cratonic basement were reactivated. Basins formed during this episode were filled by the sediments of the Aguapei, Sunsas and Huanchaca groups. These sediments are interpreted as the product of deposition as a platform cover, with extensive shallow marine by-passing to deeper marine deposition ends with fluvial sediments. In the Sunsas and Aguapei belt these middle Proterozoic sediments were affected by the Sunsas Orogeny, whereas in the Huanchaca, Santa Barbara and Rio Branco regions, they are separed of the deformation. Late Proterozoic sediments and metasediments are present along the transition zone between lhe Amazonian Craton and lhe Paraguay Belt Three major lilhostratigraphic units can be distinguished at the eastern edge of the Amazonian Craton. The basal unit comprises glaciomarine sediments deposited on shelf domain (Puga Formation) and slope environments (Cuiaba Group). ln this last environment the glaciomarine sediments were strongly reworked by turbidites currents. The middle unit includes carbonates (Araras Formation) deposited directly on top of glaciomarine sediments, which the changes laterally towards the border of the Craton to muddy limestones (Guia Formation). The upper unit consists of siliciclastic sediments (Raizama and Diamantino formations).
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