--> ABSTRACT: 3-D Geometry and Kinematics of Polygonal Minibasins and Associated Salt Ridges during Radial Spreading of Sediment Lobes above Salt, by Bruno C. Vendeville, Virginie Gaullier, and Jean Mascle; #90906(2001)

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Bruno C. Vendeville1, Virginie Gaullier2, Jean Mascle3

(1) University of Texas at Austin, Austin, TX
(2) Universite de Perpignan, Perpignan, France
(3) Geosciences Azur, Villefranche-sur-Mer, France

ABSTRACT: 3-D Geometry and Kinematics of Polygonal Minibasins and Associated Salt Ridges during Radial Spreading of Sediment Lobes above Salt

Some of the most spectacular salt structures are located on salt-bearing continental margins, along which large volumes of sediments were deposited (e.g., Gulf of Mexico, Eastern Canada, Santos and Campos Basins, Angola and Gabon, and the Mediterranean Egyptian margin). Loading of salt by sediment wedges triggers seaward spreading of both salt and overburden. Spreading takes place by proximal thin-skinned extension on the shelf and the upper continental slope and by distal contraction on and in front of the lower slope. Normal growth faults form above thin salt. Where salt is thicker, shallow grabens form, triggering the rise of underlying diapiric salt ridges. Distal contraction takes place by folding, reverse faulting, or seaward spreading of salt nappes beyond the original salt pinch-out. Seaward or landward shifts in the locus of sediment lead to reactivation in extension of older contractional structures (progradation) or reactivation in contraction of older extensional structures (retrogradation). Where the progradation front is linear, structures form parallel to the margin and the spreading direction is seaward. By contrast, in cases where the progradation front is arcuate, for example when sediments are deposited as lobes or fans, the sediment package spreads radially, forming a network of radial and concentric normal faults, under which salt rises as annular salt ridges feeding salt stocks. The salt rdiges bound polygonal fault blocks, which evolve into minibasins). Later, these salt ridges can nucleate large listric growth faults. If the regional depocenters shift laterally along the margin, the direction of spreading changes.

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