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Fiduk, Joseph C.1, Gene Brush1, Lynn E. Anderson1, Peter B. Gibbs1
(1) CGG Americas, Inc, Houston, TX
(2) Wealden Exploration, Ltd, SMarden, Kent, United Kingdom

ABSTRACT: Variations in Structural Style of Salt Bodies and Related Structures in the Espirito Santo Basin, Offshore Brazil

A combination of 3-D pre-stack and post-stack time migrated seismic data were used to examine salt bodies and related structures in the BES 2, 100, 200 and BMES 1, 2, and 9 blocks of the Espirito Santo Basin, Brazil. The seismic data covers approximately 10,600 km2 in water depths ranging from less than 600 meters to more than 2800 meters.
Seismic imaging reveals a basinward change/evolution in the structural style of salt bodies accompanied by a steady increase in salt volume, resulting in a series of structural style fairways. In shallower water, rollers form the primary salt feature but change basinward into isolated salt diapirs. Farther offshore, the diapirs develop overhangs and grow salt tongues that eventually coalesce into salt canopies. Farthest offshore, salt forms a series of stacked compressional thrust features rising from depth. Similar structural fairways have been identified in other basins along both sides of the South Atlantic margin. Differential sediment loading and down-slope gravity gliding are the primary mechanisms driving salt deformation. As a result of these processes, only a small amount of the Aptian age salt now remains at its original autochthonous level.
Salt related structural features in the sedimentary section include rotated fault blocks and detached rafts in the roller fairway, lying on the autochthonous salt weld. In the diapir and canopy fairways are numerous turtle structures and small-scale contractional features, also lying on the autochthonous salt weld. All of these structures are evidence of early loading and deformation of the original salt layer.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.