Structural modeling based on sequential restoration of gravitational salt deformation in the Santos Basin (Brazil)

Abstract

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

The role of gravitational collapse in controlling the evolution of crestal fault systems (Espírito Santo Basin, SE Brazil)

“…Important new findings have occurred in the last few decades in terms of evaluating fault growth history through seismic, outcrop, numerical and analogue modelling data (Alves, 2012;Bose and Mitra, 2010;Cartwright, 2011;Cartwright et al, 2000;Cartwright et al, 1995;Childs et al, 2009;Clausen et al, 2014;Cowie and Scholz, 1992;Garcia et al, 2012;Jackson and Larsen, 2009;Jackson and Rotevatn, 2013;McLeod et al, 2000;Morley, 2007;Yin and Groshong, 2007). The early fault growth model of Barnett et al (1987) was initially proposed to represent isolated normal faults propagating in a radial direction, and records no migration of maximum displacement points.…”

Análise de volumes de sal em restauração estrutural: um exemplo na bacia de Santos

“…A carga sedimentar do próprio sal induziu um pulso superior a 1.000 m de subsidência isostática regional (Garcia et al 2012), e o bloqueio das águas oceânicas adjacentes persistiu à subsidên-cia somente o necessário para a deposição do sal.…”

“…Os procedimentos de interpretação, tratamento dos dados e restauração estrutural das seções neste trabalho assemelham-se aos de Garcia et al (2012). O objetivo é traçar um cenário evolutivo da tectônica de sal, por meio da restauração estrutural 2D integrada à análise 3D.…”

“…A espessura do sal não deve variar aleatoriamente durante a restauração e esta variação é acompanhada por geo-história restaurada 1D, procedimento apresentado em Garcia et al (2012).…”

“…Na incerteza da restauração de mais de 2.000 m de evaporitos e na magnitude da depressão necessá-ria para acomodá-los (Montaron & Tapponnier 2010, Garcia et al 2012 entre 113 e 112 Ma, pode estar outra fonte maior das diferenças no cálculo isostáti-co (Fig. 9).…”