Estrutura litosférica da Bacia Potiguar com inversão simultânea de função do receptor e curvas de dispersão

Abstract

The opening of the South and Equatorial Atlantic during the Cretaceous gave rise to several inland and marginal basins that make up the Northeast Brazilian rifting system. The Potiguar Basin, located in the eastern end of the Brazilian equatorial margin is a product of this complex rifting process. In its onshore portion the lithospheric structure is characterized by an unusual surface heat flow with values above 101 mW/m² and low velocities of seismic waves propagation at depths below 100 km. Therefore, in order to better understand the lithospheric structure of this basin, we performed H-k stacking and joint inversion of receiver function and dispersion curves for 16 stations located in the onshore Potiguar Basin and its around. Our results show (i) a relatively thin crust (H ~30.1 km) beneath the Potiguar Basin when compared to its surroundings (H ~32 km) (ii) the existence of an ~4.3 km/s anomalous layer at depths between 30 - 40 km at most stations (iii) and the presence of a negative gradient at approximately 125 km depth that likely represents an edge between shallow lithosphere and asthenosphere (LAB). Thus, we propose that the anomalous S velocity layer just below Moho is associated with deeper magmatic intrusions and these intrusions are the result of active sublithospheric flow that keeps the basin lithosphere warm and thinned. Furthermore, we also propose that direct heating of the sublithospheric mantle may be additionally contributing to the elevated heat flux values at the surface.