The Tectonic Structure and Evolution of the Potiguar‐Ceará Rifted Margin of Brazil.

The Brazilian Equatorial Margin (BEM) is interpreted as a transform margin, where the last segment opened during Gondwana rifting. However, margin evolution, and break‐up age remain unconstrained. We interpret >10k km of crustal‐scale seismic images extending along ∼600 km of the margin calibrated with drillholes. We determine the style and timing of tectonics across the rift system. We link changes in crustal‐scale structure and age of sediment deposits to interpret variations with the style of extension and intensity of thinning across the BEM. Observations support a rift evolution where deformation is initially distributed forming a shallow basin, subsequently focusses, and later migrates basin‐ward forming the deep‐water domain. We interpret that tectonic activity started ∼140–136 Ma and stopped earlier in the shallow basin causing minor thinning, than in the deep‐water domain with a ∼60 km wide area with 4–8 km thick crust extended in Late Aptian to Early Albian (116–110 Ma). Constraints from seismic and drilling help define an abrupt continent to ocean transition (COT) where continental crust may be abutted by oceanic crust, and breakup occurred at early Albian time. Basin sedimentation from the onset to the Late Aptian is continental, indicating an isolated environment disconnected from Atlantic oceans. During late‐most Aptian to Early Albian basin sedimentation changes and indicates a comparatively rapid marine water infill. Rifting of the BEM is not dominated by transcurrent deformation as previously inferred, with strike‐slip faulting limited to comparatively small sectors, whereas most of the margin extended by normal faulting deformation. Plain Language Summary: Rifting occurs when stretching of continental lithosphere causes its extension and thinning. When extension continues, it leads to break‐up and the generation of a new spreading center. The basin is then split into two conjugate margins that diverge from each other as oceanic spreading creates new seafloor. Rifted margins attract studies as they host resources and may play a role in the impending energy transition. However, the vast majority of rifted margins are insufficiently studied. We have investigated the Brazil Equatorial Margin (BEM), the last region linking Africa and South America during Gondwana breakup, using a large seismic and drillholes data set released by industry. We investigated the tectonic structure and the sediment deposits, and how their joint analysis provides the information to unravel the history of deformation and the processes shaping rifting. Our interpretation supports that the opening of the margin was dominated by normal faulting kinematics rather than the transform‐type deformation previously inferred. Lithospheric deformation initiated with widespread distributed extension and was followed by localization of deformation causing focused thinning. Faulting later migrated basin‐ward creating <10 km thick crust forming a 50–70 km wide region. Break up and the first oceanic crust are possibly Earliest Albian time. Key Points: Newly available seismic and drillhole information provide a novel view into the development of the Brazil Equatorial MarginWe provide a new conceptual model for rifting and ages for the different processes involved, including breakup and Continental Ocean Transition formation and ageWe propose a rift model in which deformation starts distributed, later localizes, and finally faulting evolves sequentially to break up [ABSTRACT FROM AUTHOR]