Equatorial Guinea and northern Gabon margins : regional tectonic evolution based on integrated analysis of seismic reflections and potential field data and modeling
The quest to unravel and better constrain the crustal architecture and related geological processes of South Atlantic margins underscores the importance of this study. This is true considering the huge economic prospect derivable from this region, especially in the petroliferous conjugate margins of...
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| Format: | Master Thesis |
| Language: | English |
| Published: |
2008
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| Online Access: | http://hdl.handle.net/10852/12481 http://urn.nb.no/URN:NBN:no-20107 |
| Summary: | The quest to unravel and better constrain the crustal architecture and related geological processes of South Atlantic margins underscores the importance of this study. This is true considering the huge economic prospect derivable from this region, especially in the petroliferous conjugate margins of West Africa and Brazil (Cameron et al., 1999). The opening of the South Atlantic Ocean is attributed to the Mesozoic breakup of Gondwana super-continent. The breakup led to the splitting of Proterozoic cratonic blocks (e.g. Sao Francisco and Congo cratons) amalgamated during the Late Precambrian when the Brazilian and Pan African orogenies took place in the west and east parts of the cratonic nucleus, respectively (Alkmin, 2004). The evolution of varied basinal architectures within the South Atlantic conjugate margins took place in response to complex extensional and magmatic regimes initiated during the breakup process. There is a strong rheological control on the overlying Mesozoic-Cenozoic sedimentary basins along the conjugate margins, induced by the underlying different basement terranes which influence the structural evolution of the syn–rift sections (Rosendahl et al., 2005) There have been ambiguities regarding the exact position of the continent-ocean boundary during plate motion reconstructions and early stages of seafloor spreading in the South Atlantic margins. Firstly, the presence of a magnetic quiet zone from early Aptian to Campanian times is inferred as a major obstacle limiting research into anomalies arising from seafloor spreading at neighboring continental margins (Chang et al., 1992). Secondly, the presence of halokinetic structures (e.g. salt diapirs) along the South Atlantic margins blurs the efficient imaging and effective analysis of the syn-rift features (Katz et al., 2000). The bathymetric features in the South Atlantic are fairly symmetric with the central axis being the mid-ocean ridge. This ridge is confined by several structures on both sides of the abyssal plain, the most prominent being the Rio Grande Rise on the South American side and the Walvis Ridge on the African side. The study area lies between longitude 5ºE–11ºE and latitude 3ºN–3ºS. It stretches from Rio Muni in the NE to central Gabon in the SW. The evolution of these margins is ascribed to the extensional and rifting processes characterizing the South Atlantic development. Fortunately, integration of seismic and potential field data and modeling has advanced our knowledge of the deep crustal structures and fulfills the aims and objectives of this thesis which are to: (1) refine the plate tectonic, rift and shear setting; (2) study and model the crustal structure and refine the continent-ocean boundary and transition; (3) determine and refine the timing of tectonic events, and the wavelength, amplitude and timing of vertical movements; (4) refine the margin segmentation due to a number of transfer faults systems; (5) within a framework of simplified plate reconstructions, discuss the architecture and development of the conjugate Equatorial Guinea-Gabon and Brazilian margins. |
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