Tectono-stratigraphic evolution of the rift and post-rift systems in the northern Campos Basin, offshore Brazil

The Campos and Santos Basins have been a focus of subsurface studies since the discovery in 2006 of large accumulations of hydrocarbons in the Early Cretaceous rift and post-rift strata below Aptian evaporites. In this study, regional 2D seismic lines, a 3D seismic survey and well data were interpreted to reconstruct the tectono-stratigraphic evolution of the rift and post-rift stages in the northern sector of the Campos Basin. Detailed 3D seismic interpretation and geological modelling were used to subdivide the pre-salt sedimentary record. This revealed a diachronous strain distribution along the Guriri Fault System (GFS), a roughly NE-SW striking fault-bounded horst that was a focus of rift-related deformation. The syn-rift succession is interpreted to be the product of two episodes of rifting (RP1 and RP2) with contrasting fault activity patterns and lithostratigraphy. Volcaniclastics and coarse siliciclastics of RP1 were deposited under WNW-ESE transtension that formed discontinuous half-grabens followed by extensive erosion and tectonic inversion. Structurally controlled bioclastic rudstones and hybrid deposits characterize RP2 and were deposited in elongated half-grabens that delimit the GFS horst, which developed under an NW-SE extension. Deposition under increasingly less tectonically active transitional and post-rift stages dominated by thermal subsidence gradually led to the healing of the rift-related structural relief. Selective reactivation of rift faults testifies active tectonic inversion through compression from immediate post-rift throughout evaporite deposition. These interpretations are put into the context of recent geochronological data of onshore dyke emplacement and the new age constraints for the end of deposition of the pre-salt sequence. Therefore, we propose an earlier onset on rifting in the Campos Basin, at the Berriasian

Basement geology and its controls on the nucleation and growth of rift faults in the northern campos basin, offshore Brazil

The rift phase of the Campos Basin developed during the Early Cretaceous on a heterogeneous crust comprising structures inherited from the Brasiliano‐Pan African tectonic events, mostly generated during the Neoproterozoic‐Cambrian amalgamation of western Gondwana blocks. The main rifting episode took place from the Hauterivian to the Barremian, then was succeeded by the transition and post‐rift (SAG) phases during the Aptian. Rift faults developed as a result of a progressive rotation of extension from E‐W to NW‐SE. The role of pre‐existing intra‐basement structures on the style and evolution of the rift faults was investigated using 3D high‐resolution seismic data, borehole logs and sidewall samples. Three seismic facies (SF1, SF2, and SF3) and three types of intra‐basement structures (Surfaces, Geobodies, and Internal Reflections) were identified and mapped. They represent, respectively, contrasting levels of seismic anisotropy, interpreted as metamorphic foliation, and ductile shear zones that bound rock units with particular seismic facies signatures. Sidewall cores show that banded biotite‐gneiss is the predominant rock type in the eastern half of the study area, while more homogeneous granitoid is the dominant lithology on the west. Such a binary division of lithotypes is consistent with the distribution of mapped intra‐basement seismic facies and features. The contrasting basement heterogeneity across the study area is the major control in the strain distribution during rifting. Where the basement is highly heterogeneous, the pre‐existing fabric was selectively reactivated whenever its orientation was favourable, resulting in faults forming progressively as the extension direction rotates, whilst shallower low to very low angle basement fabric were cross‐cut by rift faults. Where the basement is homogeneous, only early formed faults remain active throughout the rifting

Structural framework and Mesozoic-Cenozoic evolution of Ponta Grossa Arch, Parana Basin, southern Brazil

The integration of structural analyses of outcrops, aerial photographs, satellite images, aeromagnetometric data, and digital terrain models can establish the structural framework and paleostress trends related to the evolution of Ponta Grossa Arch, one of the most important structures of the Paraná Basin in southern Brazil. In the study area, the central-northern region of Paraná State, Brazil, the arch crosses outcropping areas of the Pirambóia, Botucatu, and Serra Geral Formations (São Bento Group, Mesozoic). The Pirambóia and Botucatu Formations are composed of quartz sandstones and subordinated siltstones. The Serra Geral Formation comprises tholeiitic basalt lava flows and associated intrusive rocks. Descriptive and kinematic structural analyses reveal the imprint of two brittle deformation phases: D1, controlled by the activation of an extensional system of regional faults that represent a progressive deformation that generated discontinuous brittle structures and dike swarm emplacement along a NW–SE trend, and D2, which was controlled by a strike-slip (transtensional) deformation system, probably of Late Cretaceous–Tertiary age, responsible for important fault reactivation along dykes and deformation bands in sandstones