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Réactivation post-rift de la marge sud-est du Brésil

Nathan Cogné 1
1 Terre, Temps, Traçage
GR - Géosciences Rennes
Abstract : The southeast Brazilian passive margin is elevated and shows evidence for post rift tectonic and magmatic activity (sedimentary basins and alkaline intrusions). We undertook a structural and thermochronological study (apatite fission tracks and U-Th/He) to constrain the timing, magnitude, stress orientation and causes of the reactivations. We infer, from the modelling of thermochronological data, two exhumation phases during Late Cretaceous and Neogene over the whole studied area. A third phase during the Paleogene is restricted to the borders of the onshore Tertiary basins. The amount of exhumation attributable to post-rift reactivation from the coast to the Serra da Mantiqueira reaches about 4.5 km. The study of the seismic profiles of the Taubaté basin together with the outcrop data shown that the Tertiary basins formed under left-lateral transtension during Paleogene, with compressive stress oriented SW-NE, and was subject to right-lateral transpressive reactivation during Neogene under a roughly E-W compressive stress. Because the inferred timing and direction of stresses of the reactivation are consistent with those in other regions in the South-American plate and with the geodynamics of the Nazca - South America convergence, we conclude that the whole South American plate is under compression as a result of both ridge-push and basal tractions forces. The compression induced reactivation of inherited weak zones and uplift of the southeast Brazilian margin, leading to rejuvenation of the topography that we see today.
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Submitted on : Friday, October 5, 2012 - 3:49:32 PM
Last modification on : Thursday, January 14, 2021 - 11:38:24 AM
Long-term archiving on: : Sunday, January 6, 2013 - 3:52:00 AM

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  • HAL Id : tel-00739050, version 1

Citation

Nathan Cogné. Réactivation post-rift de la marge sud-est du Brésil. Tectonique. Université Rennes 1, 2012. Français. ⟨tel-00739050⟩

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