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RHEGMATIC-LIKE BASINS IN SICILY 3

sin). Minor positive anomalies characterise the heatflow
Northem Sicily offshore (Drepano Seamount topography
and Ustica-Aeolian Islands). Gravity values gravimetry
again increase towards the Ionian Sea (Morelli Mohodepth .
et al., 1975; Rossi & Sartori 1981; Makris &
Stobbe, 1984; Rehault et al., 1987b). Between
these two areas, an arc-shaped low anomaly
zone coincides with the Tertiary sedimentary
basins of the Sicilian-Southem Apennines
Belt (Caltanissetta Basin, Extemal Calabrian
Are and Bradanic Trough).

The Moho discontinuity (Schutte, 1978;
Finetti, 1982; Steinmetz et al., 1983; Req et
al., 1984; Finetti & Del Ben, 1986; Rehault et
al., 1987b; Locardi & Nicolich, 1988) elevates
in the Magnaghi-Vavilov and in the Marsili
areas (less than l Okm below sea level), where
the crustal thickness is less than 7 km. In these
areas, seismic studies (Recq et al., 1984) indi-
cate the presence of oceanic-type crust. The
Moho discontinuity descends towards the
peri-Tyrrhenian sectors as far as the foreland
(Hyblean and Apulia), where its deepest value
has been calculated at 25-35 km. Under the
southem Calabrian-Maghrebian Belt, the
Moho discontinuity trend indicates a crustal
superposition ofthe Tyrrhenian-Calabrian (35
km Moho depth) onto the Ionian microplate
(Schutte, 1978), where the Moho is 20 km
deep. Some strong Moho vertical discontinui-
ties can also be observed in the peri-Tyrrhe-
nian areas (as visible, for example, in Fig. l,
where between 12°-12.5° and 13.5°-14° E
long some N-S trending discontinuities cross
the Sicily areato the centrai part ofthe basin).

The Wadati-Benioff surface depth
(Caputo et al., 1972; Panza et al., 1980) is
relatively shallow under the Northern Sici-
ly-western Calabria coastal areas, but it rap-
idly increases owing to strong verticalization
in the Aeolian area, as geochemical-vol-
canological and petrographic studies bave
proved (Barberi et al., 1974; Villari, 1980; Lo-
cardi, 1985).

Fig. l. Main physical characteristics ofthe Tyr-
rhenian area. Data from: Morelli (1970), Colombi
et al. (1973), Lmi ( 1977), Schutte (1978), Panza et
al. ( 1980), Steinmetz et al. ( 1983), Della Vedova et
al. (1984, 1989), Req et al. (1984), Duschenes et
al. (1986), Finetti & Del Ben (1986), Rehault et al.
( 1987b). See text for explanation