Estrutura crustal da Bacia do Recôncavo-Tucano com inversão simultânea de dados sismológicos
The stresses that led to the opening of the South Atlantic were responsible for intracontinental extensions and, consequently, for the formation of a number of aborted rifts in Northeastern Brazil. The extension began in the Neo-Jurassic, with the formation of an Afro-Brazilian depression south of t...
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | Brasil |
| Institución: | Universidade Federal do Rio Grande do Norte (UFRN) |
| Repositorio: | Repositório Institucional da UFRN |
| Idioma: | portugués |
| OAI Identifier: | oai:repositorio.ufrn.br:123456789/43128 |
| Acceso en línea: | https://repositorio.ufrn.br/handle/123456789/43128 |
| Access Level: | acceso abierto |
| Palabra clave: | Geofísica Inversão simultânea Estrutura crustal Tectônica extensional Bacia do Recôncavo-Tucano |
| Sumario: | The stresses that led to the opening of the South Atlantic were responsible for intracontinental extensions and, consequently, for the formation of a number of aborted rifts in Northeastern Brazil. The extension began in the Neo-Jurassic, with the formation of an Afro-Brazilian depression south of the Patos Lineament, and continued in the Eoberriasian with rifting along two NS-directed deformation axes: Recôncavo-TucanoJatobá (RTJ) and Gabon - Sergipe-Alagoas (GSA). The rift progression took place north of the Pernambuco Lineament from the Neoberriasian - Eobarremian, later migrating to the West along the NE-SW trend Cariri-Potiguar (CP). In the Neobarremian, approximately coinciding with the opening of the Equatorial Atlantic, the rifting was aborted along the RTJ and CP axes, and continued along the GSA trend, eventually encountering the separation of the continents. The magmatic activity on the Brazilian continental margin seems to be restricted to the north of the Patos Lineament, represented by the dykes of the Ceará-Mirim River. The geological history of the continental rifting process in NE Brazil indicates an impact of different types of extensional efforts on the rifting styles of each sub-basin. In order to better influence efforts on possible rifting models, 11 seismographic stations were installed along and around the RTJ trend in October 2018. The installation was financed by the national oil company Petrobrás and included both short-term stations how much bandwidth. In addition, 10 more stations from the Northeast Seismographic Network (RSISNE) that were close to the study area were used. In this study, measures of crustal thickness and Vp/Vs ratios were obtained from the joint inversion analysis of receiver functions and surface wave dispersion curves and with additional constraints obtained from the H-k stacking methodology. The results show that the crust is 40 km thick below the Recôncavo and Tucano sub-basins and that it contains a thick layer (5-8 km) of high velocity materials (Vs> 4.0 km/s) below 35 km. These observations contrast with the structure immediately to the West (São Francisco Craton) and East (Borborema Province) of the basin, for which crustal thicknesses are around 44 km and 36 km, respectively, the lowest crustal velocities are below of 4.0 km/s, and local crustal thicknesses as thin as 31 km are observed. Thus, we propose, according to the 'flexural cantilever' model, that the high-speed layer that forms in the lower crust of the basin resulted from mafic underplating after stretching and thinning during a syn-rift phase, restoring the crust thickness to pre-rift phase values (or greater) providing the necessary buoyancy to initiate a regional uplift. Furthermore, although not generalized, cases of thin crust along the footwall may be related to ‘rift flank’ erosion. We conclude that, regardless of the mode of extension of the upper crust, our results favor the basin formation models that involve the extension of the lower crust by pure shear. |
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