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18 F. NIGRO
CONCLUSIONS
It was possible to propose a crustal mode! and to recon-
struct kinematic history of the Tyrrhenian Basin and sur-
rounding areas on the basis of fieid analysis of some neotec-
tonic structures outcropping in Sicily, mapping the main
neotectonic features from published and unpublished seis-
mic data, with the aid ofthe existing deep geophysical data,
and on an analysis of the literature.
The recognised neotectonic structures in mainland Sic-
ily appear, as a whole, to represent a shallow expression of
deep-seated dextral strike-slip systems affecting the Sicilian
Maghrebides. This system can be linked with the submerged
mega-structures characterising surrounding areas, that often
are represented by regional trending positive flower struc-
tures. The proposed mode! is thus based on a rhegmatic
shaping ofthe regional neotectonic evolution ofthe Centrai
Mediterranean.
The sequence of neotectonic events observed and pre-
viously described in mainland Sicily, as well as that recog-
nised through the seismic interpretations, appear to be the
result of a "pulsating" tectonics. Compressional tectonics is
prevalently represented by positive flower structures and
large out-of-sequence thrusting in the peri-Tyrrhenian areas,
while extensional tectonics is represented by rhegmatic-like
basins formation.
In the present paper, the Tyrrhenian opening is related
to the northward movement of the African plate during the
Neogene, the presence of thickened lithosphere charac-
terising the Southern Apennines-Sicilian Belt, and the Tor-
tonian-Pleistocene roll-back of the African subducted slab.
This mode! takes also into account the fact that roll-back
rate is higher than the African slab sinking rate and the
oblique convergence vectors between the Atfican-Ionian
subduction complex and the Tyrrhenian opening during the
late Pliocene-Pleistocene.
The regional N-S trend ofthe maximum compressional
axis related to the African motion is compensated for by an
extension toward the E-SE ofthe Tyrrhenian basin which in
the Magnaghi-Vavilov areas has a sphenochasm-like ge-
ometry.
The neotectonic history recorded in outcropping rock
sequences and submerged areas (especially in Sicily and in
its northern offshore) reveals that different synchronous tec-
tonic events in the Centrai Mediterranean might be in part
related to Tyrrhenian extension and African-Ionian subduc-
tion velocity vectors, even if the development of system ap-
pears have also been controlled by regional-trending shear
zones, probably activated during the tardy collisional proc-
esses ofthe Alpine Belt.
The researeh was carried aut with private jimds. The printing
was financed with private funds.
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