Salt Sediment Interactions and Hydrocarbon Prospectivity Concepts, Applications and Case Studies for the 21st Century
Insights from a Gravity-Driven Linked System in Deep-Water Lower Congo Basin, Gabon
Published:December 01, 2004
Martin P. A. Jackson, Michael R. Hudec, David C. Jennette, 2004. "Insights from a Gravity-Driven Linked System in Deep-Water Lower Congo Basin, Gabon", Salt Sediment Interactions and Hydrocarbon Prospectivity Concepts, Applications and Case Studies for the 21st Century, Paul J. Post, Donald L. Olson, Kevin T. Lyons, Stephen L. Palmes, Peter F. Harrison, Norman C. Rosen
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Deep-water structures in southern Gabon are among the best imaged in the world. Our 30-km-long study area in the Anton Marin–Astrid Marin blocks runs obliquely through the northern part of the Congo Fan. The study area is entirely covered by high-quality 3D seismic data. It spans the complex transition between the landward extensional domain and the basinward contractional domain. Both domains detach on Aptian salt. We use seismic sections and dip-corrected isochron maps to illustrate and analyze the following processes.
Control of thrust location by precursor anticlines and diapirs: a regular wavelength of the early Albian gentle precursor anticlines nucleated linear, regularly spaced thrust faults; the location of precursor passive diapirs caused some thrust faults to curve to intersect with the diapirs, linking them into the overall contractional network, which includes lateral transfer zones.
Thrusting that verged consistently seaward: most other salt-based thrust belts have less systematic vergence; we attribute the consistent vergence to the high frictional resistance of the salt detachment because it had been thinned by expulsion of salt into diapirs before thrusting began.
Landward propagation of thrusting: during the late Cretaceous and Paleogene, thrusting propagated updip through the formerly translational domain because of the buttressing effect of older thrusts downdip of the study area. In the study area, distal thrusts and diapirs were still shortening while more proximal thrusts began shortening.
Extrusion of salt sheets under compression: as thrusting culminated, the precursor passive diapirs were compressed to extrude salt; extrusion continued until the diapirs were finally squeezed shut, more or less coevally across the thrust belt in the study area.