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Variability of depositional setting along the north-western Sicily continental shelf (Italy) ... 143
ty has no considerable variation between summer and
winter, remaining between 37.6‰ and 38.2‰ (Demirov
& Pinardi, 2002).
Along the shelf and the upper slope, the Quater-
nary deposits consist of seawards dipping clastic and
terrigenous deposits coming from the northern Sicily
(Pepe et al., 2003; Agate et al., 2005), whereas in the
basinal areas hemipelagic sediments are locally interca-
lated with volcanoclastic sediments (Baghi et al., 1980).
In the continental shelf, the Pleistocene deposits
are truncated by an erosional surface formed during the
last glacio-eustatic oscillation. Local uplift caused the
systematic non-preservation of portions of the oldest
sequences (Pepe et al., 2003). Prograding sedimentary
wedges of coastal deposits formed during the Last Gla-
cial Maximum (LGM, about 18 ka) are present along the
shelf margin. The prograding wedges are absent where
the heads of the canyons or failure scars have indented
the outer shelf (Lo Iacono et al., 2011). Integrated high
resolution study based both on seismic reflection data
and on micropaleontological-sedimentological analisys
of a core collected in the outer shelf of the Gulf of Ter-
mini, allowed the recognition of two drastic sea-level
falls during the Last Glacial Maximum and the Younger
Dryas, and provided the different position of sea level
during the last 41 ky.
The Northern Sicily continental margin originated
as a consequence of a complex interaction of compres-
sional events, crustal thinning and strike-slip faulting.
Following the early-middle Miocene deformation and
thrusting of the Kabilian-Calabrian units and the most
internal units of the Sicilian-Maghrebian chain (Catalano
et al., 1985; Pepe et al., 2005), the opening of the Tyr-
rhenian Sea led to the subsidence of the northern Sicili-
an margin since the Late Tortonian (Baghi et al., 1980;
Fabbri et al., 1981). Late Miocene-early Pliocene north-
dipping high-angle reverse faults, involving mainly deep
seated, carbonate platform units, produced structural
highs (Avellone et al., 2010), among which those sea-
ward bounding the intraslope basins (Pepe et al., 2003),
termed peri-Tyrrhenian basins by Selli (1970), filled with
Late Neogene to Quaternary evaporitic, hemipelagic,
siliciclastic and volcaniclastic deposits, up to 1200 m
thick (Baghi et al., 1980). Later, normal faults partly dis-
sected the back- and fore-limb of the structural high.
Middle-upper Pliocene reflectors clearly diverge towards
the normal fault bordering the basin, thereby demon-
strating syn-extensional deposition (Pepe et al., 2003).
E-W- to NE-SW-trending normal faults exerted during
the Pleistocene a control on the morphology of the pre-
sent day shelf and coastal areas.
As a consequence two types of basins formed in
the North Sicily continental margin (Pepe et al., 2005):
(1) minor intra-slope basins (e.g. Palermo and Termini
basins) whose origin is related to the (?) late Miocene -
early Pliocene shortening and thrusting of the Sicilian-
Maghrebian Chain, and (2) major extensional basins
(e.g. Cefalù Basin) whose origin is connected to the
continental rifting which affected the internal side of the
margin during the middle (?) -late Pliocene, as demon-
strated by synextensional deposition.
The tectonic activity of the northern Sicily conti-
nental margin is outlined by a large upper plate seismici-
ty (Fig. 1), producing a seismogenic region character-
ized by compressional focal mechanisms to the west,
while in the eastern sector extensional and strike-slip
mechanisms prevail. Shallow (<25 km) seismic events
of low to moderate magnitude (max Md 5.6 on Septem-
ber 2002) occur along an E-W trending belt located
northward. The focal mechanisms related to the main
seismic shocks are in agreement with a dominant NE-
SW fault trend coupled with a NW-SE compressive off-
set direction (Agate et al., 2000; Giunta et al., 2009).
The highest uplift rates during the last 125 ky in
northern Sicily (Ferranti et al., 2010) were found on the
inner margin-terraces in the eastern coast (0.8-1.63
mm/y), whilst the Holocene rates are between 20% and
70% higher than those calculated for the Tyrrhenian
terraces. The vertical tectonic rates show a decrease
from E to W. In the Tindari promontory the rate of MIS
5.5 is 0.67 mm/y (Bonfiglio et al., 2010). The Holocene
rate is higher, as suggested by Bottari et al., (2009)
from the presence of a Holocene tidal notch at 4 m
a.s.l.. West of the headland of Tindari, Holocene mark-
ers showing increasing rate are not found, presumably
due to the coseismic activity of main structural features
active during the Pleistocene in northern Sicily: the Kabil-
ianeCalabrian Thrust Front (west of Acquedolci) and the
Vulcano-Tindari Fault (east of Patti) (Sulli et al., 2012).
Further on, both coastal geomorphological and marine
geology data between Acquedolci and Capo d’Orlando
demonstrate that while the mainland sector is uplifted,
with the same rates both during MIS 5.5 (0.34 mm/y) and
the Holocene (0.36 mm/y), contemporaneously the off-
shore area is subsiding, suggesting the existence of fault
systems parallel to the coastline, separating the inner
from outer sector of the continental shelf, causing differ-
ent vertical movements (subsidence vs. uplift) (Sulli et al.,
2012). Westwards, near Cefalù, some fossil-bearing de-
posits, dated to MIS 5, at relatively low altitude (29 m, An-
tonioli et al., 2006) indicated vertical movement rates low-
er than 0.2 mm/y. Westward, between Palermo and the
Egadi islands, many MIS 5.5 markers show a substantial
stability, except for small and local vertical movements
(Gulf of Castellammare, Mauz et al., 1997 and Castel-
luzzo Plain), due to the action of transcurrent faults where
uplift rates reach 0.1 mm/y (Antonioli et al., 2006).
3. MATERIALS AND METHODS
The morphological features of the area were stud-
ied by MultiBeam Echo Sounder (MBES) data, acquired
in different oceanographic cruises, by using both the
Reson SeaBat 8111, generating 105 beams at a fre-
quency of 100 kHz with depth range of 35-800 m, and
the Reson SeaBat 8160, which generates 126 beams
with depth range of 30-3,000 m. Bathymetric data were
acquired and stored using the PDS2000 acquisition
software. Sound velocity profiles were collected with the
Navitronic Systems AS-SVP-25. Post-processing of Mul-
ti Beam data was accomplished with the PDS-2000 sys-
tem and included the graphic removal of erroneous
beams, noise filtering, processing of navigation data and
correction for sound velocity. Gridding of the filtered
soundings was carried out to obtain the final DEM
(Fig. 2), which provided high resolution 3D views of the
sea-floor, shaded relief maps, slope maps and bathy-
metric cross sections.
Various sets of CHIRP and multi- and single-