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AFRICAN CONTINENTAL MARGINS OF THE MEDITERRANEAN SEA – Djerba, 22 - 25 November 2000

Fig.1. Geologic cross-section from the foreland to the hinterland in the Central Mediterranean

The Adventure basin, filled by Tortonian-lower Messinian sediments, is the youngest foredeep
in the western Strait of Sicily and, although it was deformed contractionally in the Messinian, it
represents the last major episode of shortening occurred in the area. However, shortening con-
tinued to operate farther to the east until Early Pleistocene, giving rise to the Plio-Quaternary
Gela foredeep. The sense of thrusting in the fold-and-thrust belt has been shown to rotate in time
from southeast in the Late Miocene to south in the Pliocene.

The onset of Tyrrhenian extension occurred in the Tortonian; such extension propagated
southeastward in time until the Early Pleistocene and affected also, to some extent, the internal
part of the fold-and-thrust belt.

The Strait of SiciIy rift zone can also be related to this episode of extension and can be seen
as a foreland response to the opening of the Tyrrhenian backarc basin.

RESULTS

The seismic profile here illustrated (Fig. 1) crosses all the domains present in the area; name-
ly, the foreland, that in this case is affected by extensional tectonics (Pantelleria rift zone), the
fold-and-thrust belt with associated foredeep (Egadi fold-thrust belt and Adventure foredeep),
and the extensional margin of the Tyrrhenian backarc basin. For each of these domains a crustal-
scale image is obtained.

A geologic cross-section has been constructed integrating the deep seismic data with data
from conventional seismic, welI logs and dredge hauls. Three major domains are represented in
the cross section: i) African foreland, ii) fold-and-thrust belt, and iii) Tyrrhenian backarc basin.

The African foreland is affected by extensional tectonics of Pliocene age that shows up as
fault systems the most prominent of which is the Pantelleria rift system. The master faults are
rather steep and bound slightly rotated blocks indicating that extension was Iimited. Along some
of the faults magmatic bodies were intruded. The maximum amount of volcanics, as interpreted
from seismic facies, appears to occur within the Pantelleria trough. The package of reflections
attributed to the Moho decreases in TWT underneath the Pantelleria trough where the maximum
crustal thinning is also indlcated by refraction data.

CIESM Workshop Series n°13 54