Page 2 - Corti_2006

84 G. Corti et al.

North America plate overrides the Pacific plate with a left lat- tral western Mediterranean (Fig. 1). Three main elements mark
eral transpression along the faster right lateral transtensional the accretionary prism of Sicily and its off-shore continuation:
transfer zone connecting the Juan de Fuca Ridge and the Baja (A) a Pliocene–Pleistocene northwest-dipping foreland mono-
California rift, as suggested by Doglioni and Harabaglia (1996). cline generating the overlying foredeep; (B) a roughly ENE-
We propose here the case of the Sicily Channel (Figs. 1 and WSW to east-west-trending thin-skinned imbricate wedge
2) as an archetype of an area where two geodynamic settings are progressively emplaced from the early–middle Miocene to pres-
active at the same time, generating a peculiar structural style that ent (e.g., Roure et al., 1990; Giunta, 1991; Catalano et al., 1996;
is a function of the related overlap. In this area, the subduction- Giunta et al., 2000); and (C) northwest-trending normal faults
related Maghrebides-Sicily-Apennines accretionary prism is and a related graben or half graben. Pliocene–Pleistocene rift-
crosscut by almost orthogonal normal faults due to an inde- ing (Figs. 2 and 3) collapsed the accretionary prism (Reuther and
pendent rifting affecting northern and northeastern Africa, both Eisbacher, 1985; Argnani, 1990; Casero and Roure, 1994; Tri-
on-shore and off-shore (Figs. 1 and 2). The geologic model is cart et al., 1994; Torelli et al., 1995), leading to the development
supported by analogue model experiments and also focuses on of the Sicily Channel, which allows the western and eastern
the structural interference pattern and its relationship with the parts of the Mediterranean Sea to connect (Fig. 1). The collapsed
related alkaline magmatism. accretionary prism has been detected in seismic reflection pro-
files (e.g., Tricart et al., 1994; Catalano et al., 1995, Catalano et
TECTONIC SETTING al., 2000a,b; Casero, 2004), showing thrusts and folds that de-
form the seafloor, indicating active deformation.
The Sicily Channel is located within a south central seg- To the northwest, the Sicily Channel rift appears connected
ment of the Apennines-Maghrebides belt developing in the cen- to the Campidano graben in southwest Sardinia (Fig. 3). The

EUROPE N
RG Carpathians

Alps Pannonian 0 200 km
Basin

Dinaride s
Black Sea
Py Apennines
VT Pb CG TS
Adriatic Sea
Fig 2
Aegean
SCh extension
Maghrebides SyCh

CG: Campidano graben
GS: Gulf of Suez LS
LS: Libyan Sea
Pb: Provencal basin
Py: Pyrenees
RG: Rhine graben GS
SCh: Sardinia Channel
SyCh: Sicily Channel Sirte basins
TS: Tyrrhenian Sea Red Sea
VT: Valencia Trough AFRICA

Figure 1. Schematic plate tectonic setting of the Mediterranean area. Extensional structures in the Sardinia and Sicily
Channels and in the Sirte region are reported in detail (after Bosworth, 1994; Skuce, 1994; Ahlbrandt, 2001). Note the
normal fault systems, shown in white, that propagate from the Sicily Channel toward the southeast into the Sirte basin,
Libya, and northern Egypt, suggesting a connection with the Red Sea rift. This extension crosscuts the Apennines-
Maghrebides accretionary prism. Therefore, it is clearly independent of the subduction system and the related back-arc
extension in the Algerian and Tyrrhenian basins. The inset shows the location of the study area, depicted in Figure 2.