Analysis of folding and deformation within layered evaporites in Blocks BM-S-8 & -9, Santos Basin, Brazil
J. Carl Fiduk, Mark G. Rowan, 2012. "Analysis of folding and deformation within layered evaporites in Blocks BM-S-8 & -9, Santos Basin, Brazil", Salt Tectonics, Sediments and Prospectivity, G. I. Alsop, S. G. Archer, A. J. Hartley, N. T. Grant, R. Hodgkinson
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The São Paulo Plateau in the deepwater Santos Basin is the site of numerous recent pre-salt petroleum discoveries. The area is characterized by a thick sequence of layered evaporites comprising primarily halite, with subordinate anhydrite and carnalite and trace amounts of other minerals. The sequence is divided into six stratigraphic packages: three relatively competent beams containing the bulk of the stronger anhydrite and three relatively weak detachment layers. Observed structural styles range from the simple to the complex, including: upright open folds, inclined thrusted folds, recumbent isoclinal folds, sheath folds and superposed folds. Multiple detachments lead to polyharmonic folding, disharmonic folding and overtightened folds. Major anticlinal structures contain acoustically transparent material surrounding disrupted, highly deformed pieces of the lower two beams. The deformation is non-coaxial, with anticlines forming a polygonal pattern and fold hinges that are highly curvilinear. The São Paulo Plateau is a contractional province that formed in response to proximal extension at the Albian Gap during convergent gravity gliding/spreading of the margin. Shortening possibly began during the waning stages of evaporite deposition, but the bulk of the movement occurred during the Santonian–Mid-Eocene. The evaporite sequence shortened much more than the cover because of extreme updip attenuation and consequent basinwards flow beneath the cover; deeper levels of evaporite exhibit more shortening due to strain partitioning across internal detachments.
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In this timely volume, geoscientists from both industry and academia present a contemporary view of salt at a global scale. The studies examine the influence of salt on synkinematic sedimentation, its role in basin evolution and tectonics, and ultimately in hydrocarbon prospectivity. Recent improvements in seismic reflection, acquisition and processing techniques have led to significant advances in the understanding of salt and sediment interactions, both along the flanks of vertical or overturned salt margins, and in subsalt plays such as offshore Brazil. The book is broadly separated into five major themes covering a variety of geographical and process-linked topics. These are: halokinetic sequence stratigraphy, salt in passive margin settings, Central European salt basins, deformation within and adjacent to salt, and salt in contractional settings and salt glaciers.