Base‐salt relief controls salt‐tectonic structural style, São Paulo Plateau, Santos Basin, Brazil. (7th July 2019)

• Record Type: Journal Article
• Authors: Pichel, Leonardo M.; Jackson, Christopher A.‐L.; Peel, Frank; Dooley, Tim P.
• Is Part Of: Basin research. Volume 32:Number 3(2020)
• Page Start: 453
• Page End: 484
• Publication Date: 2019-07-07
• Subjects: base‐salt relief -- Brazil -- diapirism -- gravity‐driven deformation -- minibasins -- ramp‐syncline basins -- salt tectonics -- Santos Basin -- São Paulo Plateau -- translation; Sedimentation and deposition -- Periodicals; Sedimentary basins -- Periodicals; 551
• DOI: 10.1111/bre.12375
• Languages: English
• ISSNs: 0950-091X

Abstract

Abstract: Base‐salt relief influences salt flow, producing three‐dimensionally complex strains and multiphase deformation within the salt and its overburden. Understanding how base‐salt relief influences salt‐related deformation is important to correctly interpret salt basin kinematics and distribution of structural domains, which have important implications to understand the development of key petroleum system elements. The São Paulo Plateau, Santos Basin, Brazil is characterized by a >2 km thick, mechanically layered Aptian salt layer deposited above prominent base‐salt relief. We use 3D seismic reflection data, and physical and conceptual kinematic models to investigate how gravity‐driven translation above thick salt, underlain by complex base‐salt relief, generated a complex framework of salt structures and minibasins. We show that ramp‐syncline basins developed above and downdip of the main pre‐salt highs record c. 30 km of Late Cretaceous‐Paleocene basinward translation. As salt and overburden translated downdip, salt flux variations caused by the base‐salt relief resulted in non‐uniform motion of the cover, and the simultaneous development of extensional and contractional structures. Contraction preferentially occurred where salt flow locally decelerated, above landward‐dipping base‐salt and downdip of basinward‐dipping ramps. Extension occurred at the top of basinward‐dipping ramps and base‐salt plateaus, where salt flow locally accelerated. Where the base of the salt layer was broadly flat, structures evolved primarily by load‐driven passive diapirism. At the edge of or around smaller base‐salt highs, salt structures were affected by plan‐view rotation, shearing and divergent flow. The magnitude of translation (c. 30 km) and the style of salt‐related deformation observed on the São Paulo Plateau afford an improved kinematic model for the enigmatic Albian Gap, suggesting this structure formed by a combination of basinward salt expulsion and regional extension. These observations contribute to the long‐lived debate regarding the mechanisms of salt tectonics on the São Paulo Plateau, ultimately improving our general understanding of the effects of base‐salt relief on salt tectonics in other basins. Abstract : Zooms of the key, most distinctive types of structures associated with complex, multiphase deformation and salt flux variations observed in different domains in the study area: (a) salt‐cored bucklefolds; (b) collapsed folds; (a‐b) transition from buckle‐folds into collapsed folds over extensional hinge at the crest of the Tupi Sub‐High; (c) reactive diapirs; (d) reactive diapirs nucleating onto salt‐cored buckle‐folds; (e) passive diapirs; (f) squeezed diapirs; (g) fold‐injection; (h) thrust‐piercement; and (i) multiphase diapirs.