Evolution of the Crustal Architecture of the Brazilian Equatorial Margin

Sparse available data and lack of seafloor spreading magnetic lineaments during the Cretaceous Magnetic Quiet Zone have caused uncertainty on the kinematic of the rifting and age of break up along the Brazilian Equatorial Margin (BEM). Here we present some new interpretation results aiming discussing the basement structure, the style of the synrift unit and define BEM`s evolution based on ~10k km of 2D seismic calibrated with exploration drillholes located from the shelf to the deepwater basin. The main seismic dataset is a grid along ~500 km of the BEM from south of Romanche Fracture Zone to Touros High. The grid is further extended with a few lines imaging the domain currently cropping out onshore calibrated with 2 wells, and a 3D volume located on a drill site on the continental shelf, and wells in the continental slope and deep-water basin. We have mapped 3 key horizons: Moho; top basement, top syn-rift. The interpretation supports an overall regional style of deformation and distribution of synrift strata which varies from south to north along the margin. In the Touros High sector the basement and synrift strata across the slope and deepwater basin are cut by steep faults that may indicate a strike-slip transform-type kinematic opening. In the central to northern sectors instead, synrift strata fill the space created by normal faults. The tectonic interpretation supports Touros High sector contains structures related to transform tectonics. The result of the infill`s calibration and basement structure analysis support a 2D evolutionary model of the BEM along Potiguar Basin which extend from the zero-extension crust in Late Jurassic to continental break-up in Early Albian. We have found 4 phases of extension triggering from an initial rift basin setting to rifted margin stage. The deformation started diffuse over a wide area cut by small faults. Subsequently, the deformation migrated towards the rift axis to then focus in a reduced area, allowing the crustal section to abruptly thin the basement across few larger faults. The deepwater margin displays 3-5 km thick basement extending for 30-50 km covered by synrift units that stop seawards into a region of 3-5 km thick basement representing the COT. Acknowledgements: We thank the Brazilian National Agency of Petroleum (ANP) for providing the seismic and drill data used in the study