Gabor C. Tari¹, Jim S. Molnar¹, Paul R. Ashton¹, Richard Hedley²

(1) Vanco Energy Company, Houston, TX
(2) Lasmo Pakistan, Karachi, Pakistan

ABSTRACT: Exploration in Syn-rift versus Post-rift Salt Basins of West Africa: Are There Significant Differences?

A critical exploration issue concerns the applicability of salt structure concepts developed in salt basins of West Africa along its entire margin. To conduct a comparative analysis, regional transects were constructed across the salt basins of Morocco, Senegal/Gambia, Equatorial Guinea, Gabon and Angola. In addition to the direct comparison of cross-sectional geometries, the map-view expression of salt tectonics were also analyzed in Morocco and Angola representing basin types with syn-rift and post-rift salt sedimentation, respectively.

Regional-scale similarities of the salt basins include the progressive complication of salt-related structures basinward, the change from an extensional domain in the shelf to a compressional domain in the slope and the presence of a toe-thrust front at the oceanward edge of the basins. Additional factors which influence the salt-deformational styles include the underlying basement structure, the original thickness and map-view distribution of salt, regional basinward tilt, and the proximity to major sediment entry points into the basin.

Regional-scale differences are partly attributed to the relative stratigraphic position of the salt in relation to the rifting of the margin. The Triassic/Jurassic salt in Morocco is located in the syn-rift sequence as opposed to the Aptian salt of Gabon/Congo/Angola which was deposited in the post-rift succession. In syn-rift salt settings, updip extension may not be the ultimate driving force for the contractional salt deformation downdip due to the lack of a basin-wide detachment efficiently linking all the salt structures together. This difference appears to impact significantly the basin-wide distribution of salt-related structural traps.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado