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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.
¨ Abstract
¨ Abstract
¨ Abstract
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Integration
of
· 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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