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Active low-angle normal faults in the deep water Santos Basin, offshore Brazil: a geomechanical analogy between salt tectonics and crustal deformation

By
MARCOS FETTER
MARCOS FETTER
Petrobras/E&P, Av. Republica do Chile, 330; 13th floor, Rio de Janeiro 20031-170, RJ Brazil
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ANDERSON MORAES
ANDERSON MORAES
Petrobras/R&D-CENPES, Av. Republica do Chile, 330; 13th floor, Rio de Janeiro 20031-170, RJ Brazil
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ANDRE MULLER
ANDRE MULLER
Catholic University of Rio de Janeiro – PUC-RIO, Av. Republica do Chile, 330; 13th floor, Rio de Janeiro 20031-170, RJ Brazil
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Published:
January 01, 2017

Abstract:

We provide a structural analysis and propose a geomechanical model for an extensional fault system observed in seismic data from the deep water Santos Basin, offshore Brazil. The system includes low-angle normal faults (LANFs) associated with underlying listric faults and salt rollers. The LANFs cut through shallow sedimentary successions up to the seafloor, reaching displacements of 1 km during the last 5 myr, at least one order of magnitude larger than the displacement of the coeval Andersonian high-angle normal faults. We suggest that the LANFs were produced by clockwise rotation of the stress field caused by the presence of salt intruded along the footwall of the main listric normal faults of the extensional system. Numerical models indicate that the proposed geomechanical model can be attained with strain weakening and widespread plastic yielding along the main normal faults. We suggest that the studied LANFs are related to salt flow in the same way that the LANFs described in regional extensional provinces are related to flow of either the lower crust or the mantle. The rheological analogy is remarkable and therefore we suggest that this work will contribute to the solution of the LANFs paradox.

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Contents

Geological Society, London, Special Publications

Geomechanics and Geology

Geological Society of London
Volume
458
ISBN electronic:
9781786203397
Publication date:
January 01, 2017

GeoRef

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