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| Titel |
Lithospheric structure of northwest Africa: Insights into the tectonic history and influence of mantle flow on large-scale deformation |
| VerfasserIn |
Meghan S. Miller, Thorsten Becker |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093806
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| Publikation (Nr.) |
 EGU/EGU2014-8888.pdf |
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| Zusammenfassung |
| Northwest Africa is affected by late stage convergence of Africa with Eurasia, the Canary
Island hotspot, and bounded by the Proterozoic-age West African craton. We present
seismological evidence from receiver functions and shear-wave splitting along with
geodynamic modeling to show how the interactions of these tectonic features resulted in
dramatic deformation of the lithosphere. We interpret seismic discontinuities from the
receiver functions and find evidence for localized, near vertical-offset deformation of both
crust-mantle and lithosphere-asthenosphere interfaces at the flanks of the High Atlas. These
offsets coincide with the locations of Jurassic-aged normal faults that have been reactivated
during the Cenozoic, further suggesting that inherited, lithospheric-scale zones of weakness
were involved in the formation of the Atlas. Another significant step in lithospheric
thickness is inferred within the Middle Atlas. Its location corresponds to the source of
regional Quaternary alkali volcanism, where the influx of melt induced by the shallow
asthenosphere appears restricted to a lithospheric-scale fault on the northern side of the
mountain belt. Inferred stretching axes from shear-wave splitting are aligned with the
topographic grain in the High Atlas, suggesting along-strike asthenospheric shearing in a
mantle channel guided by the lithospheric topography. Isostatic modeling based on
our improved lithospheric constraints indicates that lithospheric thinning alone
does not explain the anomalous Atlas topography. Instead, an mantle upwelling
induced by a hot asthenospheric anomaly appears required, likely guided by the West
African craton and perhaps sucked northward by subducted lithosphere beneath
the Alboran. This dynamic support scenario for the Atlas also suggests that the
timing of uplift is contemporaneous with the recent volcanismin the Middle Atlas. |
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