Crustal Structure and Tectonic Evolution of Early Cretaceous Continental Rift and Its Transition to Oceanic Crust in the Ultra‐Deepwater Campos Basin, Southeastern Brazil

Abstract Integration of high‐resolution gravity, magnetic, and 3D seismic reflection data provides new insights into the crustal structure and rift evolution of the Campos basin, southeastern Brazil. Gravity modeling and seismic interpretation across a 300 km‐wide passive rifted margin delineate three main structural domains: the Internal, External, and Marginal rifts. Continental crust progressively thins from 14 km nearshore to less than 5 km adjacent to oceanic crust. 3D gravity inversion was used to determine Moho depth, crustal thickness, and to define major crustal boundaries. Forward gravity modeling of four crustal types, combined with 3D seismic interpretation, demonstrates that the more seaward Marginal rift is underlain by thinned, intruded continental crust. Seismic profiles show asymmetrical half‐grabens, sag sequences, and deformed Aptian evaporites deposited within the Marginal rift adjacent to the oceanic crust. These salt deposits and magmatic features record late‐stage rifting of the Marginal rift preceding continental breakup. Comparison of the Campos margin with its conjugate margin in the Kwanza basin of Angola reveals a remarkable structural and stratigraphic symmetry between both margins that indicates synchronous crustal thinning and salt deposition prior to the onset of Albian oceanic spreading. The combined geophysical and structural evidence supports pure‐shear rifting of the Early Barremian—Late Aptian, characterized by uniform lithospheric extension, localized magmatic intrusions, and symmetrical basin development that preceded the formation of Albian oceanic crust.