Tectonic Segmentation of the Brazilian Equatorial Margin Rift

We have investigated from rift inception to break up, the tectonic structure, spatial segmentation, and temporal evolution along ∼600 km of the East-Ceará and Potiguar basins of the Brazil Equatorial Margin. We have determined the initial rift configuration, the onset of the formation of the continental margin, and its structural evolution into a Southern, Central and Northern Segments. A distinct tectonic structure and evolution, limited by abrupt boundaries, characterize each segment. The segmentation boundaries define linear trends in the basement that extend from under the continental shelf to the deep-water domain. The trend of the segment boundaries appears to delineate flow-lines of the opening direction. The geometry of the boundaries, and available fault and dike patterns, provide information on the orientation of paleo-stresses. We integrated the distribution, geometry and age of structures to produce an evolutionary model and related it to plate kinematics. The initial Phase 1 deformation occurred in a four-arms configuration, each with different opening direction. This configuration was modified during a kinematic reorientation, causing two arms to stop opening during Phase 2. Phase 2 extension focused along two arms, creating a margin-type structure, which readjusted internal deformation into a Central, Northern and Southern Segments. Rift extension continued adapting to a gradual kinematic change into a Phase 3, when the Southern Segment developed a transcurrent fault system. Margin extension ended during Phase 4 with the initiation of spreading cells with a distribution mimicking the main rift segmentation, which remained as segmentation giving rise to oceanic fracture zones.