| Abstract: | Four ductilely reworked mantled basement gneiss domes are prominent structures inside the Neoproterozoic Sergipano fold belt. The belt is an ESE-WNW trending wedge comprising sediments, metasediments, metavolcanics, and meta-intrusive rocks, and is divided into a cratonic domain to the south, passing into highly deformed miogeoclinal and eugeoclinal domains to the north. A detailed stratigraphic and structural analysis around two of these domes, in a key area spreading over the three domains, revealed that the basement domes most likely began as extensional structures controlling the distribution of sedimentary lithofacies and the variations of their thicknesses in the precursor basin of the Sergipano fold belt. Closure of the basin led to the evolution of these extensional basement structures in the core of basement-cored fold nappes. The largest of the domes is capped by a thick quartzite sequence and controlled the partition of the contractional deformation of the belt. Combined with new geophysical data, such analysis indicates that the three lithotectonic domains are continuous parts of the basin. Therefore, detailed studies of the basement-cover interface allow us to characterize the tectonic evolution of Proterozoic basins in the same way as their Phanerozoic counterparts. |
