--> Structural Development and Depositional History of the Lower Congo and Kwanza Basins Salt Tectonic Province, Angola, Guevara, Mary; Hawkins, Lisa; Joaquim, Lourenco; Johnstone, David; Jones, William; Jose, Jose G.; Oliveira, Arantes, #90100 (2009)

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Structural Development and Depositional History of the Lower Congo and Kwanza Basins Salt Tectonic Province, Angola

Guevara, Mary1
 Hawkins, Lisa1
 Joaquim, Lourenco2
 Johnstone, David1
 Jones, William1
 Jose, Jose G.2
 Oliveira, Arantes2

1PGS, Maidenhead, United Kingdom.
2
Sonangol,
Luanda, Angola.

The Angolan margin is a classic example of salt tectonics influencing subsequent sedimentation and reservoir architecture. The margin is dominated by post-Aptian salt movement brought about by the separation of Africa from South America in the Lower Cretaceous and by Cenozoic sedimentation. Interpretation of 8 regional horizons over 24,000 km2 of merged 3D seismic data located in blocks 15-19 & 34 in the deepwater Lower Congo and Kwanza Basins, offshore Angola, has helped us understand how these processes have varied through time, with fluctuations of sediment input from the Congo Drainage Basin.

Northeast-southwest profiles across the area show that there is a series of northwest-southeast trending structural zones characterised by variations in salt geometry. Grabens in the east formed by listric faults detaching in the salt layer are filled by Miocene sediments. The salt itself has largely been expelled from this zone. Towards the centre, salt pods begin to appear at high levels on the listric faults and may be disconnected from the triangular salt pedestals below them. Finally, in the southwest, salt domes extend continuously from the original salt layer upwards to shallow levels but their locations are still controlled by extensive listric faulting.

Mapping the interpreted horizons has given us an insight into the regional structural trends, tectonic evolution and the changing patterns of sand deposition which give rise to numerous large oil and gas fields and discoveries in blocks 15 to 18. The Tertiary turbidite channels affected by these structures are well imaged on RMS amplitude maps on which their variable relationships with the structures can be made out. Isochrons through each interval indicate the change through time of depocentres and sediment sources.


AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil