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| Mohriak,
W. U., J. M. Macedo, R. T. Castellani, H. D. Rangel, A. Z. N. Barros, M.
A. L. Latgé, J. A. Ricci, A. M. P. Mizusaki, P. Szatmari, L. S.
Demercian, J. G. Rizzo, and J. R. Aires, 1995, Salt tectonics and structural
styles in the deep water province of the Cabo Frio region, Rio de Janeiro,
Brazil, in M. P. A. Jackson, D. G. Roberts, and S. Snelson, eds.,
Salt tectonics: a global perspective: AAPG Memoir 65, p. 273-304. |
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Chapter
13
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| Salt
Tectonics and Structural Styles in the Deep-Water Province of the Cabo
Frio Region, Rio de Janeiro, Brazil |
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| W. U. Mohriak
J. M. Macedo
R. T. Castellani
H. D. Rangel
A. Z. N. Barros
M. A. L. Latgé |
| J. A. Ricci
A. M. P. Mizusaki
P. Szatmari
L. S. Demercian
J. G. Rizzo
J. R. Aires
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| Petróleo
Brasileiro S. A. Department of Exploration and Petróleo Brasileiro
S. A. Research Center
Rio de Janeiro, Brazil
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Abstract
The Cabo Frio region, offshore
Rio de Janeiro, lies between two of the most prolific Brazilian oil provinces,
the Campos and Santos basins. Major geologic features have been identified
using a multidisciplinary approach integrating seismic, gravity, petrographic,
and borehole data. The Cabo Frio frontier region is characterized by marked
changes in  stratigraphy and structural style and is unique among the Brazilian
marginal basins. Major geologic features include the deflection of the
coastline and pre-Aptian hinge line from northeast to east; a large east-striking
offshore graben related to salt tectonics; a northwest-trending lineament
extending from oceanic crust to the continent; basement-involved landward-dipping
(antithetic) normal faults in shallow water; a stable platform in the southern
Campos Basin; a thick sequence of postbreakup intrusive and extrusive rocks;
and, near the Santos Basin, a mobilized sequence of deep-water postrift
strata affected by landward-dipping listric normal faults. These faults
are unusual in salt-related passive margins in that they dip landward,
apparently detach on the Aptian salt, and show large late Tertiary offsets.
Locally, the older sequences do not show substantial growth in the downthrown
blocks.
South of the Rio de Janeiro
coast, a phenomenal landward-dipping fault system detaches blocks of the
Albian platform to the north and, to the south, coincides with the depositional
limit of the Albian platform. This deep-water fault system controls features
that can be mapped for hundreds of kilometers along strike and forms an
Albian stratigraphic gap tens of kilometers wide.
Two end-member processes
of salt tectonics in the Cabo Frio region result in either synthetic or
antithetic basal shear along the fault weld under the overburden: (1) thin-skinned
processes, in which the listric faults were caused by salt flow in response
to gravity forces related to massive clastic progradation from the continent;
and (2) thick-skinned processes, in which faulting was indirectly triggered
by diastrophic causes or disequilibrium in the basement topography. The
structural styles in the Cabo Frio region are compared with analogs from
other basins and with sandbox models. |
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