Coeval perpendicular shortenings in the Brasília belt: Collision of irregular plate margins leading to oroclinal bending in the Neoproterozoic of central Brazil

Abstract

Abstract The three belts which form the Tocantins province (central Brazil) records Neoproterozoic-EoPaleozoic collisions involving the Amazon and Sao Francisco paleocontinents and the Parana continental block. The Brasilia belt is a typical orocline bended around the WNW–ESE striking Pirineus Zone of High Strain (PZHS) and is comprised of the NE-trending (northern) and SE-trending (southern) segments. The Brasilia dome is an N–S elliptical structural window situated in the center of the belt, at the eastern end of the PZHS. It evidences D1–D2 and D3N shortenings (∼750–590 Ma) due to ocean closure and Amazon-Sao Francisco collision following a WNW–ESE path, and demonstrates similar evolution for both segments of the belt. However, in the southern segment, D1–D2 structures are deformed by shortening in the SW-NE direction (D3S). New data demonstrating D1–D2 and D3N tectonites deformed by D3S structures in the area close to the dome’s SW margin and SE of the PZHS support understanding the Brasilia belt and oroclinal bending as a consequence of the collision of two (Amazon and Sao Francisco) irregular continental margins leading to separation-rotation of the Parana block from the Amazon paleocontinent and the Parana-Sao Francisco collision.