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94 G. Corti et al.

prism rule out the possibility that normal faults and compressive
structures formed in a single (transcurrent or transpressive) N
geodynamic process. These observations suggest that the Sicily
Channel may be being shaped by the occurrence of two inde-
pendent tectonic processes that act simultaneously and overlap
each other: the Maghrebides-Apennines accretionary prism and
the Sicily Channel rift. The structural pattern resulting from
such a complex scenario was analyzed through scaled analogue
models reproducing the main boundary conditions inferred to
operate in the Sicily Channel. Model deformation resulted in a
complex arrangement of compressive and extensional structures
showing a close similarity to that observed in the natural case.
In particular, the main points of similarity are (1) the develop-
ment of graben systems orthogonal to the thrust fronts, (2) the Figure 13. Schematic block diagram indicating how the growing ac-
cretionary prism crosscuts while at the same time being crosscut by
contemporaneous activity of normal and reverse faults with the
the Sicily Channel rift, which allows alkaline magmatism to develop in
thrust system that is crosscut by extensional structures and vice the area.
versa, (3) prominent curvature of the thrust fronts approaching
the area affected by extensional deformation, and (4) extension
that is more pronounced in the foreland of the accretionary
same area. Moreover, the coexistence in this central Mediter-
prism with an increase in subsidence and vertical throw of ma-
ranean area of two deformational settings suggests that plate
jor graben-bounding faults proceeding southeastward (i.e.,
boundaries are passive features rather than the driving mecha-
away from the compressive structures). Comparison of seismic
nisms of plate tectonics.
sections with model cross-sections shows a strong similarity in
the geometry of structures between nature and experiments,
ACKNOWLEDGMENTS
with the coexistence of normal and reverse faults (e.g., compare
section EF of Fig. 12 with seismic line CROP M24 in Fig. 6).
We thank reviewers G. Giunta, F. Roure, and J. Wakabayashi for
Volcanic activity displays Na-alkaline affinity and a bi-
their detailed, constructive comments, which helped to improve
modal compositional distribution typical of intraplate rift-re-
the manuscript. We also thank Y. Dilek for inviting us to con-
lated magmatism. Consistent with analogue modeling, the
tribute to this volume and for copyediting the revised version of
spatial distribution of alkaline products is more diffuse in the
our article. In addition, we thank A. Argnani and M. Roveri for
foreland of the prism, where the extension is more pronounced.
providing us the grid of bathymetric data used in Figure 2 and
Additionally, the composition of the volcanic products is com-
G. Vannucci for kindly plotting these data. Discussions with E.
patible with an increase in the amount of crustal extension pro-
Carminati were very much appreciated. We thank Dr. Baldi of
ceeding southeastward. Indeed, on Pantelleria island the tectonic
the Colorobbia Italia S.p.A. for kindly providing us the quartz
setting favored the development of magma chambers, with con-
sand used in the experiments. Our research was supported by
sequent abundance of evolved products; by contrast, on Linosa
IGG-CNR (Instituto di Geoscienze e Georisorse–Consiglio
island, the more pronounced extension facilitated emission of
Nazionale delle Richerce) Pisa.
more primitive magmas. Distribution of single volcanic centers
with respect to extensional structures shows that the volcanic
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