Conjugate Divergent Margins

The main focus of the book is the geological and geophysical interpretation of sedimentary basins along the South, Central and North Atlantic conjugate margins, but concepts derived from physical models, outcrop analogues and present-day margins are also discussed in some chapters. There is an encompassing description of several conjugate margins worldwide, based on recent geophysical and geological datasets. An overview of important aspects related to the geodynamic development and petroleum geology of Atlantic-type sedimentary basins is also included. Several chapters analyse genetic mechanisms and break-up processes associated with rift-phase structures and salt tectonics, providing a full description of conjugate margin basins based on deep seismic profiles and potential field methods.
Rifting, subsidence and continental break-up above a mantle plume in the central South Atlantic
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Published:January 01, 2013
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CiteCitation
David G. Quirk, Michael Hertle, Jon W. Jeppesen, Madeleine Raven, Webster Ueipass Mohriak, Dorthe J. Kann, Mette Nørgaard, Matthew J. Howe, Dan Hsu, Brian Coffey, Marcos P. Mendes, 2013. "Rifting, subsidence and continental break-up above a mantle plume in the central South Atlantic", Conjugate Divergent Margins, W. U. Mohriak, A. Danforth, P. J. Post, D. E. Brown, G. C. Tari, M. Nemčok, S. T. Sinha
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Abstract
New seismic and well data in the deep-water basins of Campos, Santos, South Kwanza and Benguela, supported by plate reconstructions, help answer fundamental questions on the rifting history of the central South Atlantic, specifically on the amount and effect of fault-related deformation, and on when and where sea-floor spreading started. The Paraná mantle plume played a fundamental role – dynamically raising the plate, prolonging continental rifting by heat-softening the crust and, after break-up, delaying the onset of marine conditions. Previous discrepancies in extension and subsidence have been solved, and the location and age of the continent–ocean boundary can now be determined. Rifting involved approximately 450 km of homogeneous pure shear, equivalent to a β factor (lithosphere stretching factor) of 4.5. Break-up occurred at 123 Ma (Barremian–Aptian boundary), 7–8 Ma later than the southern South Atlantic but 6 Ma before widespread salt deposition. The mid-Atlantic ridge was initially subaerial, marked by a volcanic high. Sea-floor spreading was at a rate of 24 mm year−1, similar to syn-rift deformation prior to break-up. Transcontinental strike-slip shear zones are not evident but a major NW–SE lithospheric lineament associated with a failed triple junction arm had a major influence on the magmatic history, both prior to and after break-up.
A4 versions of the seismic sections shown in Figures 6 & 7 are available at http://www.geolsoc.org.uk/SUP18563.
- Atlantic Ocean
- Campos Basin
- Cenozoic
- chemically precipitated rocks
- Cretaceous
- cross sections
- crust
- evaporites
- extension tectonics
- faults
- free-air anomalies
- geophysical methods
- geophysical profiles
- geophysical surveys
- gravity methods
- igneous rocks
- lithostratigraphy
- mantle
- mantle plumes
- Mesozoic
- models
- plate tectonics
- rifting
- salt
- Santos Basin
- sea-floor spreading
- sedimentary rocks
- seismic methods
- seismic profiles
- seismic stratigraphy
- South Atlantic
- subsidence
- surveys
- tectonics
- volcanic rocks
- Benguela Basin
- South Kanza Basin
- Cruzeiro do Sul Lineament