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Crustal Structure of the Northeastern Brazilian Margin Constrained by Seismic Reflection and Potential Field Data and Modeling*
Olav A. Blaich2, Filippos Tsikalas1, and Jan Inge Faleide2
Search and Discovery Article #30060 (2008)
Posted October 25, 2008
*Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008
1ENI Norge AS, Stavanger, Norway ([email protected])
2Department of Geosciences, University of Oslo, Oslo, Norway
Integration of regional seismic reflection and potential field data along the northeastern Brazilian margin, complemented by crustal-scale gravity modeling, is used to reveal and illustrate onshore-offshore crustal structure correlations, the character of the continent-ocean boundary/transition, and the relationship of crustal structure to regional variation of potential field anomalies. The study reveals distinct along-margin structural and magmatic changes that are spatially related to a number of conjugate Brazil-West Africa transfer systems, governing the margin segmentation and evolution. Several conceptual tectonic models are invoked to explain the structural evolution of the different margin segments in a conjugate margin context and within the framework of simple-shear, pure-shear, and combined-shear deformation modes. Furthermore, the constructed transects, the observed and modeled Moho relief, and the potential field anomalies indicate that the Recôncavo, Tucano, and Jatobá rift system may reflect a polyphase deformation rifting-mode associated with a complex time-dependent thermal structure of the lithosphere. The constructed transects and the available seismic reflection profiles indicate that the northern part of the study area lacks major breakup-related magmatic activity, suggesting a rifted non-volcanic margin affinity. On the other hand, the southern part of the study area is characterized by abrupt crustal thinning and evidence for breakup magmatic activity, suggesting that this region evolved, partially, with a rifted volcanic margin affinity and character. The study clearly shows that integration of potential field and regional deep vertical-incidence and wide-angle seismic data provides a powerful resource for reducing costs and interpretation risks when petroleum exploration advances towards new frontiers.
Integration of seismic reflection and potential field data and modeling provides a reliable means of studying the NE Brazilian tectono-magmatic margin evolution, onshore-offshore structural correlations, continent-ocean boundary/transition location and character, and margin segmentation.
· powerful resource for reducing costs and interpretation risks when petroleum exploration advances towards new frontiers.
Prominent conjugate transfer systems appear to be first-order structural elements, governing margin segmentation and evolution.
It seems that the development of the Mesozoic rifting and breakup was strongly influenced by a pattern of structural inheritance from older structural features.
The evolution of the Recôncavo, Tucano, and Jatobá rift system may reflect a polyphase rifting evolution mode (pure-shear initially, and simple-shear at later stages) which is associated with a complex time-dependent thermal structure of the thinning lithosphere.
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