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| Titel |
Kinematics of the South Atlantic rift |
| VerfasserIn |
C. Heine, J. Zoethout, R. D. Müller |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 4, no. 2 ; Nr. 4, no. 2 (2013-08-01), S.215-253 |
| Datensatznummer |
250017784
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| Publikation (Nr.) |
 copernicus.org/se-4-215-2013.pdf |
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| Zusammenfassung |
| The South Atlantic rift basin evolved as a branch of a large
Jurassic–Cretaceous intraplate rift zone between the African and South
American plates during the final break-up of western Gondwana. While the
relative motions between South America and Africa for post-break-up times are
well resolved, many issues pertaining to the fit reconstruction and
particularly the relation between kinematics and lithosphere dynamics during
pre-break-up remain unclear in currently published plate models. We have
compiled and assimilated data from these intraplated rifts and constructed a
revised plate kinematic model for the pre-break-up evolution of the South
Atlantic. Based on structural restoration of the conjugate South Atlantic
margins and intracontinental rift basins in Africa and South America, we
achieve a tight-fit reconstruction which eliminates the need for previously
inferred large intracontinental shear zones, in particular in Patagonian
South America. By quantitatively accounting for crustal deformation in the
Central and West African Rift Zones, we have been able to indirectly construct
the kinematic history of the pre-break-up evolution of the conjugate west
African–Brazilian margins. Our model suggests a causal link between changes
in extension direction and velocity during continental extension and the
generation of marginal structures such as the enigmatic pre-salt sag basin
and the São Paulo High. We model an initial E–W-directed extension between
South America and Africa (fixed in present-day position) at very low
extensional velocities from 140 Ma until late Hauterivian times (≈126 Ma) when
rift activity along in the equatorial Atlantic domain started to increase
significantly. During this initial ≈14 Myr-long stretching episode
the pre-salt basin width on the conjugate Brazilian and west African margins
is generated. An intermediate stage between ≈126 Ma and base Aptian is
characterised by strain localisation, rapid lithospheric weakening in the
equatorial Atlantic domain, resulting in both progressively increasing
extensional velocities as well as a significant rotation of the extension
direction to NE–SW. From base Aptian onwards diachronous lithospheric
break-up occurred along the central South Atlantic rift, first in the
Sergipe–Alagoas/Rio Muni margin segment in the northernmost South Atlantic.
Final break-up between South America and Africa occurred in the conjugate
Santos–Benguela margin segment at around 113 Ma and in the equatorial
Atlantic domain between the Ghanaian Ridge and the Piauí-Ceará margin at
103 Ma. We conclude that such a multi-velocity, multi-directional rift
history exerts primary control on the evolution of these conjugate
passive-margin systems and can explain the first-order tectonic structures along the
South Atlantic and possibly other passive margins. |
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