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Book Chapter

Analysis of folding and deformation within layered evaporites in Blocks BM-S-8 & -9, Santos Basin, Brazil

By
J. Carl Fiduk
J. Carl Fiduk
1
CGGVeritas, 10300 Town Park Dr., Houston, TX 77072, USA
2
Present address: WesternGeco, 10001 Richmond Ave, Houston, TX 77042, USA
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Mark G. Rowan
Mark G. Rowan
3
Rowan Consulting, Inc., 850 8th St, Boulder, CO 80302, USA
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Published:
January 01, 2012

Abstract

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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Contents

Geological Society, London, Special Publications

Salt Tectonics, Sediments and Prospectivity

G. I. Alsop
G. I. Alsop
University of Aberdeen, UK
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S. G. Archer
S. G. Archer
University of Aberdeen, UK
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A. J. Hartley
A. J. Hartley
University of Aberdeen, UK
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N. T. Grant
N. T. Grant
ConocoPhillips UK Ltd, Aberdeen, UK
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R. Hodgkinson
R. Hodgkinson
Bowleven plc, Edinburgh, UK
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Geological Society of London
Volume
363
ISBN electronic:
9781862396111
Publication date:
January 01, 2012

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