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CC Attribution 3. The South Atlantic rift basin evolved as a branch of a large Jurassic-Cretaceous intraplate rift zone between the African and South American plates during the final break-up of western Gondwana. While the relative motions between South America and Africa for post-break-up times are well resolved, many issues pertaining to the fit reconstruction and particularly the relation between kinematics and lithosphere dynamics during pre-break-up remain unclear in currently published plate models.
We have compiled and assimilated data from these intraplated rifts and constructed a revised plate kinematic model for the pre-break-up evolution of the South Atlantic. Based on structural restoration of the conjugate South Atlantic margins and intraconti-nental rift basins in Africa and South America, we achieve a tight-fit reconstruction which eliminates the need for previously inferred large intracontinental shear zones, in particular in Patagonian South America. By quantitatively accounting for crustal deformation in the Central and West African Rift Zones, we have been able to indirectly construct the kinematic history of the pre-break-up evolution of the conjugate west African-Brazilian margins.
Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic pre-salt sag basin and the Sao Paulo High. Final break-up between South America and Africa occurred in the conjugate Santos-Benguela margin segment at around Ma and in the equatorial Atlantic domain between the Ghanaian Ridge and the Piaui-Ceara margin at Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of these conjugate passive-margin systems and can explain the first-order tectonic structures along the South Atlantic and possibly other passive margins.
The formation and evolution of rift basins and continental passive margins is strongly dependend on lithosphere rhe-ology and strain rates e. Buck et al. Strain rates are directly related to the relative motions between larger, rigid lithospheric plates and thus the rules of plate tectonics. A consistent, independent kinematic framework for the pre-break-up deformation history of the South Atlantic rift allows linking changes in relative plate velocities and direction between the main lithospheric plates to events recorded at basin scale and might help to shed light on some of the enigmatic aspects of the conjugate margin formation in the South Atlantic, such as the pre-salt sag basins along the west African margin e.
Huismans and Beaumont, ;. Over the past decades, our knowledge of passive-margin evolution and the sophistication of lithospheric deformation modelling codes has substantially increased e. Seton et al. However, the connections between these two scales and the construction of quantified plate kinematic frameworks for pre-break-up lithospheric extension remains limited due to the fact that no equivalent of oceanic isochrons and fracture zones are generated during continental lithospheric extension to provide spatio-temporal constraints on the progression of extension.