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Titel |
New constraints on Neogene counter-clockwise rotation of Adria relative to Europe |
VerfasserIn |
Eline Le Breton, Mark R. Handy, Giancarlo Molli, Kamil Ustaszewski |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250150913
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Publikation (Nr.) |
EGU/EGU2017-15437.pdf |
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Zusammenfassung |
The Adriatic microplate (Adria) is a key player in the geodynamics of Alpine-Mediterranean
belts because of its location between two converging plates, Europe and Africa. Most of
Adria has been subducted and is presently surrounded by deformed margins comprising
the Alps, Apennines, Dinarides and the Calabrian Arc. The Alps-Apennines and
Alps-Dinarides junctions are marked by switches in subduction polarity, with Adria being the
indenting upper plate in the Alps and the lower plate in the Apennines and Dinarides.
Reconstructing Neogene motion and rotation of Adria is therefore key to understanding
how such contrasting orogenic styles develop within a similar convergent tectonic
regime.
We propose a new kinematic reconstruction that balances shortening and extension in the
northern Apennines; it reveals that Adria rotated counter-clockwise as it subducted beneath
the European Plate to the west and to the east, while indenting the Alps to the north.
Syn-collisional back-arc extension in the Liguro-Provençal and northern Tyrrhenian basins
exceeds collisional shortening in the northern Apennines, indicating that after 20 Ma Adria
and Europe diverged. When combined with existing estimates of Neogene shortening in the
Western and Eastern Alps, this overall divergence in the Apennines constrains Adria to have
moved to the NW while rotating counter-clockwise relative to Europe. We furthermore
consider the length of the present Adriatic slab (135 km) imaged by P-wave tomography in
the southern Dinarides to represent the maximum convergence since late Paleogene
slab-breakoff, constraining Adria to have rotated 6.5˚ counter-clockwise about an axis in
northwestern Italy.
Thus, the best fit of available structural data from the Apennines, Alps and Dinarides
constrains Adria to have moved 113 km to the NW (azimuth 325˚ ) while rotating 6.5˚
counter-clockwise relative to Europe since 20 Ma. Our model predicts some 80-100
km of Neogene extension between Adria and Africa, most likely accommodated
along a NW-SE striking rift system on the African margin and by transtension along
NW-SE striking transform faults in the Ionian Sea. We propose that this Neogene
motion of Adria resulted from a combination of Africa pushing from the south, the
Adriatic-Hellenic slab pulling to the northeast and crustal wedging in the Western
Alps, which acted as a pivot and stopped further northwestward motion of Adria. |
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