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| Titel |
A new plate boundary in the Ionian Sea |
| VerfasserIn |
Alina Polonia, Luigi Torelli, Andrea Artoni, Giovanni Bortoluzzi, Claudio Faccenna, Luigi Ferranti, Luca Gasperini, Rob Govers, Carmelo Monaco, Giancarlo Neri, Barbara Orecchio, M. J. Rinus Wortel |
| 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 |
250095984
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| Publikation (Nr.) |
 EGU/EGU2014-11464.pdf |
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| Zusammenfassung |
| The Calabrian Arc (CA) is a narrow and arcuate subduction system resulting from
Africa/Eurasia plate convergence and slab rollback in the Tyrrhenian region. The very slow
present-day plate convergence suggests a decrease in subduction efficiency, but underplating
may still be active in the central CA where GPS data suggests an outward motion
of Calabria relative to Apulia. Shortening in the accretionary wedge is taken up
along the outer deformation front and out-of-sequence thrust faults (splay faults).
Transtensive deformation accounts for margin segmentation along transfer tectonics
systems bounding different margin segments. Transfer faults represent the shallow
expression of deeply rooted processes at the slab edge. One of these structures is
the NNW-SSE trending transtensive STEP (Slab Transfer Edge Propagator) fault
system located East of the Malta Escarpment from the Alfeo seamount to the Etna
volcano.
Margin segmentation occurs along a second NW-SE trending crustal discontinuity
delimiting two distinct lobes of the subduction complex close to the Messina Straits region.
The Western Lobe (WL) of the subduction complex, offshore Sicily, is a down-dropped and
very low tapered (about 1.5°) wedge detaching on the base of the Messinian evaporites. The
Eastern Lobe (EL), in front of Central Calabria, shows a more elevated accretionary wedge,
steeper topographic slopes, higher deformation rates and a deeper basal detachment. High
resolution tomographic images suggest a strong interplay between structural development
and slab dynamics: the WL corresponds to areas where the slab is detached, while beneath
the EL the slab is continuous.
Newly acquired geophysical data (Urania cruise, October 2013), reveal that the
deformation zone between the two lobes of the accretionary wedge displays fresh seafloor
scarps and mud volcanoes suggesting it represents an active tectonic boundary and a deep
fluid/mud conduit.
We propose that this discontinuity is a new plate boundary segment in the Ionian Sea,
connecting the compressive belt in northern Sicily to the Hellenic Arc system and dissecting
the CA subduction complex. This deformation zone accommodates differential movements of
the Calabrian and the Peloritan portions of CA and can explain the NW-SE extension
observed in the straits of Messina as well as the relative motion between Calabria and NE
Sicily.
This reconstruction is in agreement with geodetic data and earthquake slip vectors
observations which suggest the existence of a microplate in the central Mediterranean. The
discontinuity between the two lobes would thus represent a major component of the
southwestern (hitherto poorly constrained) boundary of this microplate. The motion of
Africa relative to Eurasia would be accommodated along this structure by relative
rotations between the different blocks resulting from African plate fragmentation. |
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