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| Titel |
A deep mantle origin for the asymmetry of the South Atlantic margins |
| VerfasserIn |
N. Flament, M. Gurnis, S. Williams, M. Seton, R. D. Müller, J. Skogseid |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064656
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| Zusammenfassung |
| Amongst the salient features of the margins of the South Atlantic are the deep Argentine
Basin and the Elevated Passive Continental Margins of Northeast Brazil and Southern Africa.
The origin and the age of this asymmetry of the margins of the South Atlantic are subject
to debate. For instance, the amount of Cenozoic uplift in Southern Africa varies
depending which observations are emphasized, the Argentine basin has been attributed
either to shallow asthenospheric flow or to dynamic topography, and the Brazilian
Highlands have been attributed either to continental-scale far-field stresses associated
with Andean convergence or to the interaction of a plume tail with thick cratonic
lithosphere.
In order to better understand the origin and age of the asymmetry of the margins of the South
Atlantic, we developed a workflow to investigate the effect of mantle dynamics on deforming
continents. This workflow consists in a) global plate reconstructions, generated using the
GPlates software, that account for continental deformation deduced from published
geological and geophysical data and plate reconstructions; b) imposing the kinematics of
such reconstructions in forward global mantle flow models, computed using the 3D-spherical
finite-element code CitcomS, in which compositionally distinct crust and continental
lithosphere are embedded within the thermal lithosphere. Our plate reconstruction for
the South Atlantic, based on that of Torsvik et al. (2009), accounts for intraplate
deformation in both Africa and South America, lithospheric stretching at passive margins,
and mountain building along the convergent margin of South America. We have
investigated the interaction between mantle flow and lithospheric stretching and their
contributions to surface topography in passive margins systems. In particular, the
contributions to topography of lithospheric stretching, thermal cooling and deep
mantle flow (dynamic topography) are simultaneously quantified in the case of
pure shear of the lithosphere. Our model reproduces the first-order asymmetry of
the South Atlantic margins. We attribute the large subsidence of the Argentinian
margin to the dynamic topography induced by ongoing subduction along the narrow
southern portion of South America. In addition, we suggest that part of the uplift of
Southern Africa can be attributed to its motion away from this dynamic topography
low.
Reference
Torsvik, T. H., Rousse, S., Labails, C., and Smethurst, M. A., 2009, A new scheme for the
opening of the South Atlantic Ocean and the dissection of an Aptian salt basin, Geophys. J.
Int. 177, 1315–1333. |
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