- 1Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Geophysics, São Paulo, Brazil (sacek@usp.br)
- 2Universidade de Brasília, Instituto de Geociências
Two major styles of Mesozoic rifting occurred in the SW Atlantic. Along the eastern coast, north of Rio de Janeiro, oceanic crust formed shortly after the initial extensional phase with little lithospheric stretching. In contrast, along the southeastern coast, a high degree of lithospheric stretching occurred, leading to a large area of now-subsided stretched continental crust before the final rupture and oceanic crust formation.
Numerical modeling of rifting processes indicates that a prolonged stretching phase can result from a low-strength lithospheric lid or a more ductile lower crust. A lower crust with a more felsic composition (higher quartz content) tends to be more ductile. We compiled previously published bulk Vp/Vs ratio results from receiver function studies to investigate a potential systematic compositional difference between the eastern and southeastern continental coasts. However, no systematic difference was identified that could explain the two distinct rifting styles.
On the other hand, recent continental-scale seismic tomography maps consistently show that the lithospheric lid (100–150 km depth) in the eastern continental margin has higher seismic velocities compared to the southeastern margin. This suggests that the high degree of lithospheric stretching in the southeastern margin may be attributed to a low-strength lithospheric mantle.
New thermomechanical numerical simulations of lithospheric stretching are presented, taking into account lateral compositional inheritances and initial thermal anomalies. These simulations quantify how variations in lithospheric mantle rigidity can influence the architecture of the margin, controlling its width and asymmetry. The numerical results are compared with different segments of the margin to evaluate whether compositional or thermal inheritances in the mantle (e.g., related to the influence of the Tristan da Cunha mantle plume) can partially explain the differences in rifting styles.
How to cite: Sacek, V., Assumpção, M., Gosling, G., Monteiro da Silva, R., Rocha, M., Nascimento, A., and Affonso, G.: Rifting style of the SW Atlantic margin determined by lithospheric strength, as revealed by seismic tomography and receiver functions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5053, https://doi.org/10.5194/egusphere-egu25-5053, 2025.
