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| Titel |
The influence of mantle convection on the evolution of South American topography during the Miocene |
| VerfasserIn |
Nicolas Flament, Michael Gurnis, Dietmar Müller |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250050207
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| Zusammenfassung |
| The effect of mantle convection on the topography, dynamic topography, has been the subject
of considerable interest over the past few years. South America is a key area to study this
phenomenon since it has been drifting west over subducting oceanic lithosphere for the last ~
130 Ma.
To quantify the evolution of dynamic topography, a workflow has been developed that
consists of imposing kinematics from tectonic reconstructions developed using the software
GPlates as a surface boundary condition in global mantle convection models computed with
CitcomS. Using this workflow for South America, Shephard et al. (2010) suggested that
changes in dynamic topography over the last 30 Myr contributed to the establishment of the
eastward drainage of the Amazon River. Nevertheless, both geodynamic models and tectonic
reconstructions can be improved to gain further insights on the contribution of mantle flow to
the evolution of the topography of South America. In purely viscous geodynamic
models, subducting slabs can be obtained by running an initial velocity boundary
condition for ~ 100 Myrs or by using an adjoint method in which the present-day
mantle seismic structure of the mantle is assimilated in time-dependent models.
Both of these methods are computationally expensive, and adjoint methods depend
on the resolution of tomography models that is limited for South America. We
introduce a new slab assimilation method in which the thermal structure of the
slab, derived analytically, is progressively assimilated in the upper mantle into the
dynamic models. In addition, this method allows us to model flat slab segments
that have been proposed for the Andean margin and that are particularly relevant
for dynamic topography. Furthermore, our new models account for continental
deformation. They include a reconstruction of the tectonic shortening along the
Andean margin that affects the evolution of the location of the trench. In addition, we
divided the South American plate into nine individual rigid blocks, as suggested by
recent reconstructions of the opening South Atlantic Ocean. Finally, we model
tectonic extension along the Eastern margin of South America, which allows us to
calculate the tectonic subsidence due to both continental stretching and to dynamic
topography.
Reference:
Shephard, G. E., Müller, R. D., Liu, L. & Gurnis, M., 2010. Miocene drainage
reversal of the Amazon River driven by plate–mantle interaction. Nature Geosci. 3,
870-875. |
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