Page 2 - Basin_formation_the Egadi

286 F. Gamberi, A. A r g m n i / Tecronophysics 252 (1995)285-294

seismic grid allows to map small-scale structures, sheets in interna1 position, while those in external
and although the basin is related to extensional fault- position consist of the Oligocene-Early Miocene
ing, a complex pattem of contractional features has quartzarenitic Numidian flysch (Antonelli et al.,
been recorded within the basin fill. These structures 1988).
might reflect the activity of the diverse tectonic
settings that surround the basin. Farther north, in the Sardinia Strait, two main
metamorphic tectonic units, the Sardinian unit (SU)
2. Geologic setting and the Calabro-Peloritani-Kabylian (CPK) unit,
are superposed, in a stack of south-directed thrust
The Egadi FTB represents the linkage between sheets, on top of the Egadi FTB (Catalano et al.,
the Sicilian and the African Maghrebides. It is com- 1989) (Fig. 1).
posed of a stack of thmst sheets, detached from their
substrata and overthmst towards the southeast during From Messinian to Recent times, extensional
a Middle-Upper Miocene compressional event faults were active in the rear of the structural edifice,
(Argnani et al., 1987). These thrust sheets formed a while convergence and crustal thickening were going
NE-SW-trending imbricate fan with ramp and flat on at the thrust front (Roure et al., 1990). This
geometry (Argnani et al., 1987). Late Triassic-Early extensional phase led to the opening of severa1 basins
Tertiary carbonates and shales made up the thrust with variable amount of extension and to the origin
of the Tyrrhenian back-arc basin (TBAB) (Fabbri et
al., 1981; Sartori, 1990).

In the Sardinia Strait, the low-angle north-dipping

Fig. 1. Simplified skeich of the main stmctural elements of the Strait of Sicily and surrounding areas. The box indicates the study area.
TBAB = Tyrrhenian back-arc basin; SU = Sardinian unit thmst front; CPK = Calabro-Peloritani-Kabylian thmst front.