Continental-scale structural heritage from rift extension to postrift inversion: Implications for the central Brazilian Equatorial Margin evolution

The link between major basement anisotropies and basin evolution is crucial for understanding the role of tectonic inheritance on continental margins. However, it is still a matter of debate how and why it happens, especially in the Equatorial Atlantic, where the interplay between Precambrian fabric and the shearing of major oceanic fractures has been studied. Here, we investigate the offshore Cear??a Basin and its basement in the central part of the Brazilian Equatorial Margin to (1) map basement anisotropies underneath marginal basins and show how Precambrian crustal domains influenced basin evolution; (2) determine the deformation style of reactivated basement faults; and (3) assess the interplay between reactivated faults and the oceanic Romanche Fracture Zone. The combined geological and geophysical data show that reactivation of NE-SW to ENE-WSW continentalscale ductile shear zones that acted as crustal weakness zones started in the Early Cretaceous under a normal stress field. Stress field inversion occurred in the Barremian during the continental breakup when the South American plate started to became an independent intraplate area under a strike-slip stress regimes. The shear zones arrest at the E-W-striking Romanche Fracture Zone, which marks the continental-oceanic boundary. The major fault offsets occurred along the Transbrasiliano Shear Zone, which represented a collisional boundary between paleocontinents in the Neoproterozoic. Fault reactivation also occurred in the eastern boundary of the Cear??a Terrace marginal ridge along the Transbrasiliano Shear Zone, uplifted during tectonic inversion. We conclude that fault reactivation mainly occurred between contrasting Precambrian terrains separated by ductile shear zones. Additionally, the folds associated with the Romanche Fracture Zone were mainly generated along reactivated faults that affected syn- to postrift units on the Equatorial Margin.

Automated summary

This study investigates the offshore Cear??a Basin and its basement in the central part of the Brazilian Equatorial Margin to understand the influence of Precambrian crustal domains on basin evolution, determine the deformation style of reactivated basement faults, and assess their interaction with the oceanic Romanche Fracture Zone.