David Lopes de Castro

Turbidite systems are key marine sedimentary formations found in passive continental margins, serving as major hydrocarbon reservoirs in deepwater fields worldwide. Since the 1970s, prolific hydrocarbon accumulations associated with turbidite deposits have been discovered in post-salt sequences along the Brazilian eastern margin. Recently, the margins of the Equatorial Atlantic, both in South America and Africa, have become major exploration frontiers, whose giant oil fields are found in Late Cretaceous turbidite systems. This study investigates turbidite systems in the central Brazilian Equatorial Margin using seismic data and direct hydrocarbon indicators (e.g., gas chimneys, paleo-pockmarks, flat and bright spots). These interpretations were further supported by special seismic attributes that enhance signals in both low- and high-frequency bands, improving the delineation of depositional features. The interpreted seismic patterns were also correlated with analogous responses observed in productive oil fields of the Equatorial Atlantic basins, including those of the Brazilian margin and previously studied West African basins. Three main turbidite complexes were mapped within the Brazilian oblique-transform margin segments between the St. Paul and Romanche oceanic fracture zones, encompassing the Pará–Maranhão, Barreirinhas and Ceará basins. These turbidite systems are associated with major unconformities and structurally controlled by rooted normal faults in the acoustic basement. The integration of seismic facies, attributes, and direct hydrocarbon indicators reveals strong similarities with established hydrocarbon plays in South American and African basins, achieving good chronostratigraphic alignment with the tectonic and depositional evolution of the Equatorial Atlantic margin. However, this study primarily describes potential geological risk reduction based on seismic interpretations, rather than providing definitive proof of an active petroleum system in still largely unexplored frontier basins.

The Brazilian Equatorial Margin (BEM) is an oblique-transform continental margin inherited from the Pangea breakup and the opening of the Equatorial Atlantic Ocean. Located in the central portion of the BEM, the Barreirinhas Basin is a frontier region with only three deep-water wells. Efforts have been made to understand its tectono-depositional evolution and potential for petroleum exploration. This study provides the first integrated characterization of fluid migration systems in the offshore Barreirinhas Basin, identifying and mapping seismic indicators, as well as connecting them with regional settings. We analyzed conventional 2D and 3D seismic reflection data, integrated with available well data. Additionally, seismic attributes (instantaneous amplitude, pseudo-relief, similarity, and chaos) were applied to enhance the interpretation of conventional seismic profiles. Our results show diverse fluid migration features, from deep strata to the seafloor, constrained in four main migration systems. Two systems are correlated to regional gravitational collapse. Fluid conduits, pockmarks, mounds, and faulted zones indicate focused fluid flow. A third system is developed in a region dominated by transform tectonics related to the Romanche Fracture Zone, in which dense fault networks are observed within a laterally extensive interval from the slope to the basin plain. The fourth system is located in a broad region of the basin plain, characterized by numerous seafloor mounds associated with fluid conduits and seismic indicators of hydrocarbon accumulation. These findings improve the knowledge about an underexplored basin and provide a foundation for the understanding of fluid migration systems and their implications, including marine processes and products, emplacement of igneous bodies, and hydrocarbon prospectivity.

A Margem Equatorial Brasileira (MEB) surgiu como uma área de significativo interesse científico e econômico devido ao seu alto potencial petrolífero, evidenciado por importantes descobertas ao longo das margens conjugadas do Atlântico Equatorial. Este estudo investiga a influência da Zona de Fratura Romanche (ZFR) na evolução tectono-sedimentar da Bacia de Barreirinhas, localizada no setor central da MEB. Com base na análise integrada de cinco seções sísmicas e dados de poços exploratórios, foram identificadas estruturas típicas de ambientes transtensionais, incluindo falhas normais listricas subverticais e estruturas em flor negativa, afetando tanto o embasamento quanto as sequências sedimentares sobrejacentes. Essas feições demonstram forte controle tectônico initiada ZFR sobre a morfologia da plataforma continental, talude continental e a compartimentalização interna das sequências rifte e drifte. A evolução da Bacia de Barreirinhas reflete uma interação complexa entre rifteamento oblíquo, regime de falhas transcorrentes e reativações tectônicas posteriores, classificando-a como uma bacia do tipo pull-apart. A configuração atual da margem, marcada por segmentos estruturais distintos, ressalta o papel fundamental das zonas de fratura oceânicas na gênese e no desenvolvimento de bacias ao longo da BEM. Os resultados apresentados contribuem para uma melhor compreensão dos controles estruturais sobre os sistemas petrolíferos na margem equatorial e destacam a importância de estudos futuros, envolvendo modelagem estrutural e caracterização geofísica tridimensional.

The Rio Grande Rise (RGR) is the largest oceanic plateau in the South Atlantic and represents a key natural laboratory for understanding oceanic plateau formation, deep-sea circulation, ecosystem functioning, and ferromanganese crust development. This study presents a critical synthesis of current scientific knowledge on the RGR, integrating geological, geophysical, oceanographic, biological, and geochemical evidence published over the last two decades. Geophysical data reveal a complex tectono-magmatic evolution involving Late Cretaceous plume-related volcanism, crustal thickening, rifting, and subsequent subsidence. The structural framework of the plateau is dominated by the Cruzeiro do Sul Rift, which plays a central role in controlling sedimentation, magmatism, and seawater circulation. Oceanographic studies demonstrate that the interaction between the southern branch of the South Equatorial Current and the complex topography of the RGR generates intense internal tides and bottom currents, strongly influencing sediment transport and benthic habitats. Biological investigations indicate that the RGR hosts diverse deep-sea communities, including sponge grounds, cold-water corals, and associated fauna, whose distribution is tightly linked to geomorphology and hydrodynamics. Ferromanganese crusts occurring on the plateau preserve valuable geochemical records of oceanographic and redox conditions, although their spatial distribution, thickness, and metal budgets remain incompletely constrained. Despite major advances, significant knowledge gaps persist regarding crustal structure, sedimentary evolution, ecosystem functioning, and mineral formation processes. This review highlights these uncertainties and outlines research priorities necessary to improve understanding of oceanic plateaus and deep-sea systems in the South Atlantic.

This study promotes a comprehensive geophysical mapping of the Potiguar Basin Precambrian basement with unprecedented detail, using thermomechanical analysis of the lithosphere, advanced anomaly enhancement techniques, an unsupervised semi‐automatic mapping method (SOM) and 2D/3D joint magnetic‐gravity modelling constrained by seismic and well data. This Early Cretaceous multiphase marginal basin, located at the northeastern end of the Brazilian transform margin of the Equatorial Atlantic, conceals in its onshore portion an aborted rift overlain by thin post‐rift deposition. The combined analysis of Curie‐Point Depth, Effective Elastic Thickness and Moho relief reveals six distinct crustal domains, providing a refined understanding of the lithospheric structure and its response to the plate‐driven motion that caused the crustal thinning and rifting. Analysis of magnetic and gravity patterns, lineaments and SOM populations integrated with magnetic susceptibility‐density models and key geophysical transects over the study area demonstrates the complex Precambrian basement grain dominated by intensively deformed shear zones and sets of grabens and horsts within the rifted zone. Our results highlight that the Potiguar Rift intricate internal architecture preserves evidence of the strong structural control exerted by the pre‐existing structural framework on the nucleation and evolution of this intracratonic rift, and its subsequent abandonment. This geological setting emphasizes the Potiguar Basin as a key case study of tectonic inheritance role at the lithospheric, continental, basinal, and fault‐scales.

The karstification of carbonate rocks creates 3D maze voids that are normally controlled by fracture networks and sedimentary bedding. The spatial distribution and density of karst systems are usually complex and difficult to predict, demanding multidisciplinary studies at different scales of investigation to determine the spatial distribution and density of karst features and their possible links with cave systems controlled by the regional structural setting. The present study integrates geophysical datasets (gravity, electrical resistivity tomography - ERT, and ground penetrating radar - GPR) with a digital elevation model to investigate a karst system in the Irecê basin, a semiarid region of Brazil. Morphostructural lineaments reveal a NNW-SSE- and E-W-oriented structural setting of the crystalline basement, which is imprinted on the internal basin architecture, and surface drainage network. Negative gravity anomalies and high-gradient gravity zones indicate the main karstic zone, where karst landforms are concentrated. In addition, 2.5D gravity modeling provides the internal basin geometry, demonstrating that the karst system has evolved in the thickest sector of the basin. ERT profiles delineate the underground passages that connect dolines at depth. Finally, GPR data image shallow subsurface ghost-rock karstification that spread out from the surface to depth and that took advantage of vertical fractures and slightly arched bedding planes. Our results point out the role of the fracture corridors in channelizing hydrodynamic energy at a sufficiently high level to create caves by the total removal of dissolved material, whereas in the surrounding areas under low hydrodynamic conditions, overall shallow ghost-rock karstification took place, creating residual weathered rocks (alterites).