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| Titel |
Inversion of back-arc basins : example of the Ligurian Basin, Western Mediterranean |
| VerfasserIn |
Françoise Sage, Marie-Odile Beslier, Jean-Xavier Dessa, Laure Schenini, Louise Watremez, Bernard Mercier de Lépinay, Virginie Gaullier, Christophe Larroque, Nicole Béthoux, Nicola Corradi, Aurélien Bigot, Sébastien Migeon, Ana Ruíz-Constan |
| 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 |
250099835
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| Publikation (Nr.) |
 EGU/EGU2014-15668.pdf |
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| Zusammenfassung |
| The Mediterranean back-arc basins, once opened, are often rapidly submitted to inversion
along the complex Eurasian-African convergent border. Along their continental margins,
these small basins consist of heterogeneous systems that juxtapose lithospheres with different
nature, mechanical behavior and structural inheritance. In this study, we focus on the northern
Ligurian margin to examine how such complex systems might deform when they are
submitted to compressive stress. The northern Ligurian margin, of Oligo-Miocene age,
has been undergoing contraction over at least the last ~6 Ma. Below the margin,
active thrust faults responsible for the regional uplift of the continental edge have
been proposed in previous works, but have never been imaged. Seaward of the
margin, no recent or active crustal compressional structure has been identified so far
in the oceanic domain, although seismicity extends as far as midway through the
basin.
We use seismic reflection data, including 72- and 12-channel high-resolution acquisitions
(MALISAR, 2006 and FABLES, 2012) and 96-channel deep-penetrating ones (MALIS,
1995), to image the Ligurian margin and the adjacent oceanic domain. In the seismic lines,
the Messinian event, well dated over the Mediterranean (5.96-5.32 Ma) and well
identified in the seismic stratigraphy, allows us to quantify the vertical deformation
over the last 5.3 Ma. The seismic reflection data set is interpreted together with
3D-velocity-depth models deduced from wide-angle seismic data (GROSMARIN,
2008).
Below the margin, the contraction is characterized by folds, south verging thrusts, tilted
crustal blocks, and by a global margin uplift that exceeds 1500m. Within the adjacent oceanic
domain, noticeable deformation is restricted to large, SW-NE elongated salt walls located 10
to 40 km from the margin toe, over a 70 km length. We interpret them as resulting from
combined deep-seated crustal and thin-skinned deformations. However, although the salt
walls are well expressed in the seafloor morphology, their seismic images do not reveal any
significant vertical throw across their trace, and the amount of deformation gradually
disappears toward the structure ends. This suggests that the post-Messinian deformation taken
along these features is moderate, compared to the margin. The synchronicity of the
crustal deformation in the oceanic and the continental domains supports the idea
that the lower deformation amounts observed within the deep basin are related to
different mechanical behaviours within the continental margin and the adjacent
oceanic domain, rather than the result of a recent basinward propagation of the
deformation.
Thermo-mechanical models suggest that mainly two factors could control the focused
deformation along the margin: (1) the locus of highest topographic gradient of the main
crustal interfaces, (2) the thermal contrast between the subsiding cooling oceanic domain and
the uplifting warming margin. According to these models, the continental versus oceanic
nature of the lithospheres would be of second order in the localization of the deformation. |
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