Page 1 - Basin_formation

Page 1 - Basin_formation_the Egadi

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TECTONOPHYSICS

ELSEVIER Tectonophysics 252 (1995) 285-294

Basin formation and inversion tectonics on top of the Egadi
foreland thrust belt (NW Strait of sicily)

Fabiano Gamberi * ,Andrea Argnani

Istituto per Iu Geologiu Marina-CNR. Via Gohetti 101, 40129 Bolognu, Iluly
Received 3 1 May 1994; accepted 9 February 1995

Abstract

Extensional basins are known to occur on top of the Apennine Maghrebian fold-and-thrust belt that runs along Sicily and
peninsular Italy. They formed mainly during the Plio-Quatemary, presumably in relation to the opening of the Tyrrhenian
back-arc basin, while contraction was active at the thrust front. Contractional structures are often present within their
sedirnentary infill. One of these basins, INVO-2 located southwest of the Egadi Islands, has been investigated using a closely
spaced grid of multichannel seismic reflection profiles in order to define its structural style. Basin INVO-2 was formed along
a system of NW-SE-trending extensional faults and is subdivided into two subbasins separated by a morphologic high.
Flipping of half-graben polarity is often encountered along the axis of the two subbasins. Contractional structures, trending
both perpendicular and parallel to the basin axis, occur within the basin infill, and in some instances these structures can be
related to reactivation of previous extensional faults. Although the lack of well contro1 does not allow a precise dating of the
contractional episodes, they appear to occur intermittently, frorn the onset of the basin until recent tirnes, intercalated to a
dominant extensional regime. The origin of compressional pulses in this extensional setting can be looked for in the
dynarnics of the adjacent Maghrebian collision zone.

1. Introduction nine-Maghrebian subduction (Malinverno and Ryan,
1986). Extensional tectonics was active at least since
The Maghrebides and Apennines constitute a the Messinian while compression was going on at
Neogene Foreland Thrust Belt (FTB) within the the same time in the extemal side of the FTB
Mediterranean Alpine orogen that runs along North (Patacca et al., 1990).
Africa, Sicily and peninsular Italy (Fig. 1). This FTB
is dissected in its interna1 side by extensional faults In some of these basins related to extensional
which disrupted the orogenic edifice and generated tectonics and occurring in the surrounding of the
severa1 sedimentary basins. The final result of this Egadi Islands it has been shown, studying commer-
activity was the opening of the Tyrrhenian basin cial seismic profiles, that the Plio-Quatemary sedi-
which is a back-arc basin with respect to the Apen- mentary infill is affected by contractional suuctures
(Catalano and Milia, 1990; Gamberi and Argnani,
* Corresponding author. 1993). This paper deals with the tectonic evolution
of one of these basins (basin INVO-2; Fig. 2) where
reflection seismic profiles have been collected on top
of the commercia1 seismic. The close spacing of the

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