International audienceThe structural restoration of two parallel cross-sections in the central portion of the Santos Basin enablesa first understanding of existent 3D geological complexities. Santos Basin is one of the most proliferousbasins along the South Atlantic Brazilian margin. Due to the halokinesis, geological structures presentsignificant horizontal tectonic transport. The two geological cross-sections extend from the continental shelfto deep waters, in areas where salt tectonics is simple enough to be solved by 2D restoration. Such crosssectionsdisplay both extensional and compressional deformation. Paleobathymetry, isostatic regionalcompensation, salt volume control and overall aspects related to structural stylewere used to constrain basicboundary conditions. Several restoration algorithms, such as simple shear, flexural slip and free methods,were used to restore the sedimentary deformation, including salt gravity gliding. The results of the 2Drestoration are consistent with five major sequences of sedimentary evolution: (1) the brittle pre-saltdeformation, (2) the significant and fast salt deposition, (3) the initial post-salt deformation with predominantrafting tectonics, (4) the Late Cretaceous progradational deposition and coeval development ofcompressional minibasins, and (5) the Cenozoic sedimentary deposition, with less intense salt tectonics. A1D subsidence analysis based on the 2D restored results is shown as a useful restoration control tool. The 1Dresults indicate that an initially proximal infill evolves towards distal regions under salt tectonics control. The1D diagrams also record the history of the overburden movements through lateral depocenter migration inminibasins areas, submitted to large horizontal salt spreading. The results highlight an important isostaticmovement during salt deposition, large but not enough to eliminate a needed depression to accommodatethe thick evaporites. By quantifying the halokinetic lateral deformation through time, the results suggest lessintensity of the phenomenon throughout the Paleogene, with minor impacts on the petroleumsystemin thisperiod
42(2): 433-450, junho de 2012Arquivo digital disponível on-line no site www.sbgeo.org.br 433 ResumoA complexidade da halocinese na porção central da bacia de Santos envolve expressivas estruturas e depocentros deformados, diferenciados ao longo da direção de deformação principal. Cinco seções geológicas, com registro estratigráfico completo na área de estudo, foram restauradas para investigar diferentes estilos de deformação, incluindo a evolução da falha de Cabo Frio, coerentemente inserida na evolução tectonossedimentar da bacia de Santos. O procedimento integrou a restauração 2D com tratamento e análise 3D, por meio das seguintes etapas: remoção de camadas, descompactação e compensação isostática flexural; restauração desacoplada da tectônica do sal; conservação material (inclusive do sal); recomposição da sobrecarga sedimentar quando diferentes taxas de distensão afetam os domínios desacoplados; calibração batimétrica do conjunto restaurado e tratamento e análise espacial dos resultados. O detalhamento em 14 etapas de restauração foi suficiente para tratar a deformação de forma não contínua, minimizou desvios do método e produziu consistência geométrica e estratigráfica dos resultados no domínio espaço-tempo. A redistribuição controlada do sal confirmou os efeitos do aporte sedimentar e as estruturas preexistentes sobre a deformação. Os resultados demonstram a importância da reciprocidade dos efeitos de deslocamento lateral por halocinese sobre isostasia, batimetria e descompactação, não considerada nos programas de restauração existentes.Palavras-chave: geologia estrutural; balanceamento de seções; tectônica de sal; bacia de Santos; análise de bacias. AbstractAnalysis of salt volumes in structural restoration: an example of Santos Basin. Halokinesis complexity in the central portion of Santos Basin involves significant structures and deformed depocenters, differentiated along the tectonic transport direction. Five geological cross-sections with an entire stratigraphic record in the study area have been restored to investigate different deformation styles, including the evolution of Cabo Frio Fault, coherently inserted into the tectonosedimentary evolution of Santos Basin. The procedure combines 2D restoration with 3D treatment and analysis through the following steps: layering removal, decompaction and flexural isostatic compensation; decoupled restoration of salt tectonics; material conservation (including salt); retrieval of the layering when differential strain rates affect uncoupled domains; bathymetric calibration of the restored set, and treatment and spatial analysis of results. Detailing of 14 restoration steps has properly discretized the deformation, minimized procedure deviations, and provided geometric and stratigraphic coherence in the space-time domains. The controlled salt redistribution has confirmed the effects of sedimentary aggradation and pre-existing structures on the strain. The results highlight the reciprocity importance of the effects of the halokinetic lateral displacement on isost...
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