DYNAMICS and ACTIVE PROCESSES - International Lithosphere ...

ILP TASK FORCE on SEDIMENTARY BASINS
2010 International Workshop
November 7-12, 2010, Tirana (Albania)
ALPINE INVERSION of the NORTH AFRICAN MARGIN and DELAMINATION of
its CONTINENTAL LITHOSPHERE
François ROURE* , **, Piero CASERO***, and Belkacem ADDOUM****
*IFP Energies Nouvelles, 1-4 Avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
**VU-Amsterdam, de Boelelaan 1085, 1081HV Amsterdam, the Netherlands
***Roma, Italy
****Sonatrach, Division Exploration, Avenue du 1° Novembre, BP68M, Boumerdes 35000,
Algeria
corresponding author: Francois.ROURE@ifpenergiesnouvelles.fr
The former Mesozoic passive margin of North Africa has been strongly influenced by the
Cretaceous to Neogene Alpine deformations, making difficult to trace its initial contours
between the Saharan Atlas and Apulia in the west, and its current extent and architecture
beneath the allochthon of the Ionian-Calabrian arc and adjacent Mediterranean Ridge in the
east.
A rim of Tethyan ophiolitic sutures can be traced more or less continuously from Turkey and
Cyprus in the east, in onshore Crete, in the Pindos in Greece and Mirdita in Albania, as well
as in the Western Alps, Corsica and the Southern Apennines in the west, implying that both
the Apulia/Adriatic domain and the Eastern Mediterranean Basin belong to the southern
margin of the Tethys. Because there is no evidence of vertical offset of the Moho beneath the
Mediterranean arcs, we propose to apply a new model of delamination of the continental
lithosphere, recently documented in the southeastern Carpathians, to the Apennines and the
Aegean, where the paleo-oceanic suture is indeed exposed in the hinterland. According to this
model, only the mantle lithosphere of Apulia and the Eastern Mediterranean has been and is
still locally subducted and recycled in the asthenosphere, the northern portion of the African
crust and coeval Moho being currently decoupled from its former, currently delaminated and
subducted mantle lithosphere.
Although the Kabylides and Peloritan units have been for a long time assumed to be of
European affinities, there is no evidence of any ophiolitic suture in Algeria, Tunisia nor Sicily
between the stable African foreland and these far-travelled accreted terranes. Therefore, the
former substratum of the Tellian units still remains conjectural, this intervening domain being
either related to a truly oceanic or instead to a formerly thinned but still continental
lithosphere.
Accurate dating of the synflexural and synkinematic series helps to trace the spatial and
temporal evolution of the regional foreland flexure developing in front of advancing nappes,
and which indeed records the effects of thrust loading and slab pull. Synorogenic sediments
help also to precise the timing of thin-skinned deformation, which occurred mainly prior to
the Upper Miocene in Algeria, but was still active during the Pliocene and even the
Quaternary in the Southern Apennines and along the eastern margins of the Ionian abyssal
plain.
Despite non-cylindricity and time discrepancies in the tectonic/geodynamic agenda, regional
cross-sections presented here show also many similarities in the deformation of the lower
plate between the Tellian edifice in Algeria in the west, the Sicilian Channel between Tunisia
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