Regional-residual separation and enhancement methods applied to regional analysis of potential data: Structure of Florianopolis and Rio de Janeiro fracture zones in the western South Atlantic

Abstract

Topographic, gravimetric and magnetic data has been employed to map regional tectonic elements in the South Atlantic presenting major oceanic tectonic structures which had previously lacked continuity when approaching the continental margin. The creation of such contoured maps has proven that numerical transform methods involving regional/residual separation and derivatives of gravity and magnetics can enhance geophysical signatures and unveil hidden structures, especially in the transition from the continental margins to the oceanic basin. In assessing the tectonic trend of the Florianopolis and Rio de Janeiro fracture zones close to the Brazilian continental margin, the fracture zones change direction from E-W in the oceanic region to NE-SW in the continental margin, probably displaced by the cretaceous hinge line in the northern portion of the Santos Basin. The continental structures associated with possible transcurrent and transfer zones that gave rise to the fracture zones of Rio de Janeiro and Florianopolis, probably played an essential role in the evolution of both the SE margin of the Santos Basin and the African conjugated margin. Analysis demonstrates the magnetic and gravimetric signatures of fracture zones can serve as important constraints for reconstructing continental margins in the rift and post-rift.