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| Titel |
Intracratonic basin subsidence: a legacy of continental break-up? |
| VerfasserIn |
John Armitage, Francis Lucazeau, Claude Jaupart |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077218
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| Zusammenfassung |
| Intracratonic basins are enigmatic, large, and very long-lived sedimentary basins that exits
across all the continental landmasses. After formation the subsidence history continues for
hundreds of millions of years, providing a potential archive of change in climate and mantle
dynamics. Subsidence within these basins initiates during periods of break-up and dispersal
of super-continental assemblies. The long-lived subsidence history then contains
episodic periods of uplift and subsidence at intervals of 20 to 50 Myr. We propose
that intracontinental basins are formed by extension of the lithosphere, related to
continental break-up. The subsequent episodic subsidence is driven by the lateral
density contrast at the transition from oceanic to continental lithosphere at the passive
margin.
Continental lithosphere is melt depleted, buoyant and thick. It will resist convective
breakdown into the asthenosphere below, but will be prone to lateral flow due to horizontal
density contrasts. Changes in lithosphere thickness at the transition between continent and
ocean will nucleate convection cells. Using a numerical model of viscous upper
mantle flow we show that stability or instability of the continental lithosphere at
a passive margin is a function of the lithospheric rheology and composition. In
model simulations, a continental lithosphere thought typical of the Phanerozoic
continental platform experiences a topographic fluctuations due to an evolving array of
convection cells in the mantle. The timing and magnitude of predicted changes in
topography are similar to those observed at the eastern North American margin and
the Congo Basin in Africa. The open question is if these small-scale instabilities
will eventually lead to the onset of subduction and the destruction of the margin. |
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