Deformation band evolution along a major transfer zone in the cretaceous tucano rift basin, NE Brazil

• Autor(a) principal: Peralta Gomes Júnior, Cleber
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/44/44141/tde-24072023-082710/
• topic: Deformation bands; não disponível; Rift transfer zone; Subseismic structures; Tucano Basin

The Cretaceous Tucano Rift basin exhibits notable examples of subseismic structures, i.e. cataclastic deformation bands and related structures, that help to unravel the pre-Gondwana breakage and South Atlantic opening geologic framework. We investigate the structural kinematic evolution of subseismic structures, their geometry, distribution, frequency, orientation and kinematics within and away from a first order rift transfer zone. The Vaza-Barris rift transfer zone probably acted allowing displacement between arranged en-echelon segmented extensional rift axes and connecting major faultbounded depocenters of minor sub-basins. The great dominance of north to northeastoriented deformation band faults agrees with the overall structure of the rift, revealing that the majority of the subseismic structures are compatible with the regional stress field responsible for the basin formation. The very steep normal-slip subseismic structures and high rake striation (dip-slip to high-oblique) in slip surfaces are similar both within and away from the transfer zone. Local strike-slip deformation bands are found only along the transfer zone and at the basin borders, possibly recording local stresses related to fault tips and transfer faults, thus suggesting a transtensional strain regime. Different orientation of subseismic structures occur only in pre-rift successions to the east of the area, related to the proximity of major seismic-scale faults and possibly different regional stress fields. Deformation bands within sandstones of the so-called post rift Banzaê Member of the Marizal Formation studied in this work suggests a late rift pulse or continued rifting during the Aptian. Due to cataclasis, these subseismic structures introduce a macro permeability anisotropy in reservoir rocks that should be taken into consideration during well planning and hydrocarbon injection or production situation