Interpretação sismoestrutural da porção ocidental do rifte Potiguar (Nordeste do Brasil)

Abstract

The Potiguar rift is part of the basin ensemble belonging to the Cariri-Potiguar trend, formed during rifting initiated in the Late Cretaceous. The filling of the rift is closely related to its tectonic stages of development (rift, post-rift and drift). With the aim of contributing to the understanding of the western portion of the Potiguar rift, the main objective of this monograph is to analyze the interrelations of tectonic structures, as well as the kinematic arrangement between them, focusing on the syn-rift section, based on the analysis of a 3D seismic volume. The interpretation of seismic volume 0303_3D_SOLEDADE relied on the prior application of seismic filters and attributes, selected to increase the signal-to-noise ratio and emphasise structures. The structural framework presents a segment of the Apodi fault, which exhibits a dominant normal dip-slip, a curvilinear profile, and NW-SE orientation. Due to variations in the geometry of the Apodi fault, it is possible to divide the area studied into two structural sectors: (i) a north-western sector in which there is a low density of second-order normal faults; and (ii) a south-eastern sector in which there is a greater occurrence of faults and associated folds. Second-order normal dip-slip faults affect the basement, exhibit a rectilinear profile, and trend WNW-ESE, classified at times as synthetic or antithetic relative to the Apodi fault. The interval relating to the sedimentary package also shows faults with oblique orientations (WNW-ESE and E-W) relative to the Apodi fault and dipping to the NE or SW. In addition, associated structures induced by faulting were interpreted, such as drag folds, or even folds formed by the propagation or bending of faults. Mapped seismic horizons delineate the top of the acoustic basement and the boundary between syn-rift and post-rift sections. The first shows an asymmetrical hemi-graben trough geometry with an axis orientated in a NW-SE direction, while the upper horizon shows gentle seismic relief. From the seismostructural analysis, indications of positive reactivation of the Apodi fault were also observed, evidenced by an asymmetric antiform (harpoon structure) and southwest vergence of the axial surface.