--> The Conjugate Margins of the South Atlantic: Exploration of Deeper Plays, by Patrick Unternehr, Philippe De Clarens, and Simon Russell; #90037 (2005)

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The Conjugate Margins of the South Atlantic: Exploration of Deeper Plays

Patrick Unternehr1, Philippe De Clarens2, and Simon Russell1
1 Total, Paris, France
2 Total

The kinematic evolution of the South Atlantic is relatively well understood through the identification of the marine magnetic seafloor spreading anomalies together with the morphotectonic data on the oceanic transform faults.

Nevertheless, the initial reconstructions near the continental margins are, relatively speaking, poorly constrained because of several factors: the 'disappearance' of the classical oceanic markers (and thus isochrons, transform faults) as the margin is approached, the difficulties in properly identifying the continent-ocean boundary, the uncertainty on the estimation of the stretching factors...

In this work, the use high resolution global gravimetric data set and a structural interpretation of the large seismic data base existing at TOTAL on these margins has allowed us to produce initial reconstructions of the conjugate margins with a higher degree of detail.

These reconstructions show the initial structural geometry (segmentation, transfer faults, asymmetry of the tilted blocks and depocenters) of the reconstituted rift system between Africa and South America with 3 main margin-parallel segments: the northern equatorial transform segment, the central salt divergent segment and the southern volcanic segment.

We show through different examples that this structural pattern strongly controls the sedimentation, the petroleum systems and the thermicity of potential deep plays below the 'classical' turbiditic plays including the synrift sequences. Finally, the high resolution nature of these reconstructions allow us to understand better the intra-plate deformations in Africa and South America and to explain the major problem of the 'closing' of the South Atlantic, mentioned by Bullard in 1965 and still not resolved today.