Recent discoveries in Cretaceous presalt basins of the South Atlantic have brought industry’s attention to a new deep-water play on the conjugate margins of South America and Africa. Some of the key factors impacting exploration success in rifted basins are: basement composition, compartmentalization, and subsidence history. Definition of the continent-ocean boundary and configuration of the passive margin are generally inferred from the extent of identified oceanic magnetic anomalies, paleo plate reconstructions, and presence of evaporites. In the absence of magnetic lineations on oceanic crust during the “Cretaceous quiet period,” the margin configuration at the onset of oceanic spreading in the Atlantic is open for debate.

The Equatorial Atlantic Transform Margin was dominated by shear deformation due to adjustment in relative plate motions during separation of North American and African plates to the north and South American and African plates to the south. Rifting along the passive margins adjusted to variations in spreading rate, mantle thermal structure, and rift geometry. To reveal the original basin shape, filtered Bougüer gravity and seismic reflection data were used and aided by modeling of South Atlantic opening. This approach provided boundary conditions for original basin shape and limits of extended continental crustal.