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.
Continental break-up along strike-slip fault zones; observations from the Equatorial Atlantic
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Published:January 01, 2013
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CiteCitation
M. Nemčok, A. Henk, R. Allen, P. J. Sikora, C. Stuart, 2013. "Continental break-up along strike-slip fault zones; observations from the Equatorial 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
The study focuses on Equatorial Atlantic margins, and draws from seismic, well, gravimetric and magnetic data combined with thermo-mechanical numerical modelling.
Our data and numerical modelling indicates that early drift along strike-slip-originated margins is frequently characterized by up to 10°–20° spreading vector adjustments. In combination with the warm, thinned crust of the continental margin, these adjustments control localized transpression.
Our observations indicate that early-drift margin slopes are too steep to hold sedimentary cover, which results in their inability to develop a moderately steep slope undergoing cycles of gravitational instability resulting in cyclic gravity gliding. These slopes either never develop such conditions or gain them at later development stages.
Our modelling suggests that the continental margin undergoing strike-slip-controlled break-up experiences warming due to thinning along pull-apart basin systems. Pull-apart basins eventually develop sea-floor spreading ridges. Margins bounded by strike-slip faults located among pull-apart basins with these ridges first undergo cooling. However, spreading ridges leaving the break-up trace along its strike eventually pass by these cooling margins, warming them again before the final cooling proceeds. As a result, the structural highs surrounded by several source rock kitchens witness a sequential expulsion onset in different kitchens along the trajectory of spreading ridges.
Discussion of the methods used, chronostratigraphic results and strike-slip margin characteristics are available at http://www.geolsoc.org.uk/SUP18518
- Africa
- Atlantic Ocean
- Brazil
- continental crust
- continental margin
- Cretaceous
- crust
- crustal thinning
- Equatorial Atlantic
- faults
- geophysical methods
- geophysical surveys
- gravity methods
- gravity sliding
- magnetic methods
- Mesozoic
- numerical models
- plate tectonics
- rifting
- sea-floor spreading
- sedimentary cover
- seismic methods
- South America
- strike-slip faults
- surveys
- tectonics
- thermomechanical properties
- West Africa
- Ghana Ridge