Deep seismic structure of the continental margin in the Gulf of Guinea: a summary report

Abstract

Post-stack reprocessing of the PROBE seismic data set has resulted in a refined tec-

Crustal breakup and continent-ocean transition at South Atlantic conjugate margins

“…In particular, along the northeastern Brazil-Gabon conjugate margin, the data set was provided courtesy to Statoil and comprises seismic reflection profiles acquired by TGS-NOPEC (Camamu/Almada basins) and ION-GXT (South Gabon Basin). Published seismic reflection [Rosendahl et al, 1991;Meyers et al, 1996aMeyers et al, , 1996bRosendahl and Groschel-Becker, 1999;Rosendahl et al, 2005] and wideangle refraction profiles [Wannesson et al, 1991] along the Gabon margin have also been analyzed, revised and incorporated into our interpretations. Farther south, along the conjugate southeastern Brazil-Angola margin, industrial reflection seismic profiles acquired by Fugro Multi Client Services (Espírito Santo Basin) were at our disposal.…”

“…Two such end-member margins have been subjected to intense debate, the "magma-dominated" and the "magmapoor" margins. In this context, possibly anomalous crust located within the continent-ocean transitional domain has been recognized along several margin segments in South Atlantic and described variously as 'proto-oceanic crust,' 'attenuated continental crust', and 'transitional crust' [e.g., Meyers et al, 1996aMeyers et al, , 1996bRosendahl and Groschel-Becker, 1999;Wilson et al, 2003;Moulin et al, 2005;Rosendahl et al, 2005]. However, in most of the passive margins worldwide the nature and the precise evolution of the crust at the transitional domain from early rifting to breakup of the continental lithosphere is still unclear and several alternative models have been proposed [Whitmarsh et al, 1996;Wilson et al, 2003;Rosendahl et al, 2005;Kusznir and Karner, 2007;Afilhado et al, 2008;Reston, 2009a].…”

“…Similarly, the asymmetric behavior as observed on the conjugate margins along the central segment may be controlled by the existence of an inherited strong lower crust along the West African margin, as well as by detachment faulting (Figures 3a and 6). The existence of an enigmatic high-velocity/high-density lower crustal body along the West Africa margin of the central segment is well documented [Wannesson et al, 1991;Meyers et al, 1996b;Rosendahl and Groschel-Becker, 1999;Contrucci et al, 2004;Moulin et al, 2005;Blaich et al, 2010]. However, the origin and nature of this anomalous lower crustal body is debated and may be interpreted variously as high-grade metamorphic crustal rocks, a mixture of mafic and ultramafic crustal rocks or serpentinized mantle [Contrucci et al, 2004].…”

“…However, the origin and nature of this anomalous lower crustal body is debated and may be interpreted variously as high-grade metamorphic crustal rocks, a mixture of mafic and ultramafic crustal rocks or serpentinized mantle [Contrucci et al, 2004]. The peculiar and characteristic landward-dipping structures observed within the lower crustal body (Figure 3a) [Rosendahl et al, 1991;Rosendahl and Groschel-Becker, 1999], however, may be correlated with Pan-African age structures mapped on land [Rosendahl et al, 1991]. Furthermore, the high-velocity/ high-density lower crustal body has clearly affected the rift evolution of the central segment, however, the assumption that breakup related volcanism along the central segment was not voluminous, implies that the anomalous lower crustal body is most likely unrelated to breakup.…”

Determination of the Structural Lineaments in the Kribi-Campo-Ma’an Area from a Multi-Scale Analysis of Gravity Data Using the HGM and Euler 3D Deconvolution Approaches

“…These are mainly characterised by the Kribi-Campo Fault (KCF) system which is herein defined as a continuation of the Sanaga Fault [1]- [3] [14] [15]. Other studies [16] [17] supported by [18] also link the KCF to an offshore fault system known as the Kribi Fracture Zone inferred as the eastern end of the Ascension Fracture Zone settled during the W Gondwana break-up.…”