Seismic interpretation and structural modelling (physical and computational) of structures of the Brazilian equatorial margin with emphasis on the Potiguar Basin
Baixa Grande fault; Post-rift inversion; Structural modelling; Distensional folding; Potiguar Basin
The Potiguar Basin is located at the intersection of the eastern and equatorial Brazilian margins and includes a sedimentary fill that registers its different evolutionary stages: Rift, Post-Rift and Drift. The Rifte stage was particularly important because it gave rise to the structural framework of the basin, result from two distinct events related to the openings of the East (Rift I - Neocomian) and Equatorial (Rift II - Eoaptian). In both cases, all the structures are covered up by deposits of the other evolutionary stages of the basin. Thus, in addition to the essential use of seismic data for structural analysis, physical and computational structural modeling can help in understanding how the evolution of these structures occurred. In this context, this work aimed to define the structural framework of a portion of the onshore Potiguar Rift (Rift I) through 2D and 3D seismic data and the construction of physical and computational models that simulate the origin and evolution of the observed structures. The analysis of the seismic sections revealed a tectonostratigraphic framework composed of 2 semi-grabens (Umbuzeiro and Boa Vista) separated by an important structural high (Quixaba High), all with a NE-SW trend. The border faults of these semi-grabens have the same direction, normal dip slip and different geometries: listric for the semi-graben of Boa Vista and in flat-ramp for the one of Umbuzeiro (Baixa Grande fault). This fault presents variation in the geometry along its extension, which is responsible for the folding of overlying sin-rift strata, giving rise to important synforms and antiforms in the area. In some sections, it was observed segments of this fault affecting the Post-Rift and Drift strata, characterizing at least one post-campanian reactivation event. The observed secondary faults present normal or reverse dip slip with soft to strong dips, and may occur rooted in the basement or inside the sedimentary fill. Finally, the preliminary physical and computational models simulated the flat-ramp geometry of the Baixa Grande fault and confirmed a distensional origin for the interpreted folds.