The first comprehensive geological and geophysical surveys of the Brazilian continental margin during the 1970s recognized the crust in the SE Brazilian basins as 'anomalous' but models for the opening of the South Atlantic proposed at that time invoked a very narrow continent-ocean transition. Nevertheless, such studies established the presence of a thick sedimentary prism, including an extensive salt layer under the São Paulo Plateau. The earliest reconstructions for the South Atlantic invoked a seaward shift of the spreading axis to account for the asymmetric widths of the salt layer between the Brazilian margin and its conjugate in offshore Africa.Although our understanding of continent -ocean transition has progressed since then, direct seismic imaging at crustal scale has only been possible recently through long offset (10 km), deep recording (18 s), pre-stack depth migrated (PSDM) to 40 km, seismic-reflection data. These data allow us to generally image the Moho from under thick continental crust (.30 km) to thin oceanic crust (c. 5 km). Although the nature of the transitional crust is still contested, these seismic data allow for constraints on various models for continent -ocean transition. Future integrated studies utilizing PSDM and refraction-seismic data will further refine these models.

The Lower Congo Basin and Congo Fan of Angola contain giant oil discoveries in Oligocene & Miocene deep-water sands; the Late Cretaceous and Tertiary fans in the Campos Basin of Brazil contain some 90% of Brazil’s reserves. Petroleum exploration in these vast, deep-water regions is resource-hungry, increasing the value of techniques that facilitate quick and inexpensive extrapolation from discoveries into undrilled areas. Our work demonstrates a strong correlation in these basins between reservoir fairways and various attributes of the gravity signature. We provide comparisons between published interpretations based on well and seismic data and our interpretations of gravity attribute images. We demonstrate the use of geographic information systems (GIS) techniques to facilitate the comparisons, discuss the possible basis for these correlations and speculate on their application to other basins. We conclude with notes on current research to improve the resolution of the gravity data and future refinements to our processing and interpretation methods.

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Recent discoveries offshore Tanzania and Mozambique highlight East Africa as an emerging world-class pet-roleum province. Oil and gas estimates for this province total 12.5 BBO and 250 TCFG (Brownfield et al., 2012) as yet undiscovered. Play-opening reservoir systems have been verified in Paleocene, Eocene, and at least two Oligocene deep-water submarine fan and intraslope channel complexes (Law, 2011). In deep-water Tanzania, there have been seven gas discoveries (of eight attempts) since 2010, with recent announcements putting total gas reserves in Tanzania at 24–26 TCFG. In neighboring Mozambique, 19 wells were completed by Anadarko and ENI in the Ruvuma Basin from 2009 to June 2012, only two of which were not announced as commercial discoveries. With the additional drilling, the increase of reported reserves now approaches or exceeds 100 TCFG. Evidence continues to mount that suggests the Late Cretaceous section contains deposits from similar depositional settings (Tanzania Petroleum Development Corporation, 2003). There are also indications that the petroleum system may contain oil as well as the established gas.

Abstract:The main objective of this book is to provide a global overview of divergent margins based on geological and geophysical interpretation of sedimentary basins along the South, Central and North Atlantic conjugate margins, from plate tectonics and crustal scales to a more detailed description of stratigraphical and structural elements that are responsible for petroleum plays. These themes are complemented by geodynamic concepts based on physical and numerical models, and by comparisons with present-day embryonic margins, which are succinctly discussed in some papers.