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Variability of depositional setting along the north-western Sicily continental shelf (Italy) ... 153
tary prism, although present, does not extend to the m a.s.l., may be related to the succession of compres-
edge). sional and extensional tectonic events recorded in the
margin during the Plio-Quaternary.
Type 2 are depositional shelves (prevalent or ex-
clusive sedimentary origin), in which the pre-Calabrian 7. CONCLUSIONS
bedrock is buried by a considerable thickness of Qua-
ternary sediments and does not significantly influence The integrated analysis of morphobathymetric and
the sea floor morphology; seaward progradational out- high resolution seismic data collected on the continental
building contributes more than one half of the entire shelf to slope system was used to illustrate the present
shelf width. Also in this case it is possible to distinguish stratigraphic and morphostructural setting of the North
two subtypes (Fig. 12): 2A are shelves in which the sub- Sicily continental margin and its Late Neogene-Quater-
strate deepen regularly seaward; 2B are shelves in nary geological evolution.
which the structural setting determines a substrate uplift
in correspondence of the current position of the shelf We recognized an upper Pleistocene-Holocene
break (in this case the substrate is at shallow depths, sedimentary succession, deposited during the last eu-
providing a support for sedimentary prism accumulate static change (last 125 ky). This succession, interpreted
and expand). The depositional shelves occur in the Cas- as a IV order depositional sequence (LQDS), shows
tellammare, Palermo and Termini Imerese gulfs repre- along the different sectors of the margin considerably
senting the 2A type, the type of continental shelf most variable internal geometry and different stratigraphic
widespread in the area. In this type of shelf we can find, relationships with the underlying units. The lower
in the inner platform, thick Holocene sedimentary wedg- boundary of the LQDS is represented by a subaerial
es that are absent in the shelves of the first type. erosional surface formed during the last eustatic sea
level fall, ended in the LGM (20-18 ka), and shaped
When we compare stratigraphic architecture and again during the Late Quaternary-Holocene sea level
depositional setting observed in the north-western Sicily rise. This unconformity lies at the top of a seaward dip-
offshore with other Tyrrhenian margins, there is a striking ping Pleistocene succession whose depositional archi-
similarity mostly with the offshore Calabria and Cam- tecture is in turn controlled by Quaternary eustatic sea-
pania. In these sectors we can observe depositional (type level fluctuations.
2) shelves along the gulfs, e.g. Gulf of S. Eufemia (Chioc-
ci et al., 1989) and Gulf of Salerno (Aucelli et al., 2012); Even if depositional sequences in this margin are
otherwise, predominantly rocky shelves (type 1) are wide- the result of the interaction between sea level changes
spread in front of morpho-structural salient, e.g. Punta and sedimentation, the tectonic activity has played a key
Licosa (Trincardi and Field, 1991; Ferraro et al., 1997) role, not only to determine the different characters of
and Capo Suvero (Mongardi et al., 2004). This type (1) of each sequence in different areas, but also in the creation
continental shelf, characterized by prograding shelf mar- of different types of continental shelves. As a conse-
gin deposits and absence of thick coastal prisms, is also quence we recognize different types of continental shelf
common along linear margin (without coastal embay- with different stratigraphic and morphostructural settings,
ment) with scarce sedimentary supply, e.g. Marettimo identified on the basis of the occurrence and thickness of
Channel, in the Egadi islands area (D’Angelo et al., the LQDS deposits: a) type 1, predominantly rocky
2004), and Tuscan Islands (Roveri & Correggiari, 2004), shelves, both accompanied by a moderate frontal sedi-
or along epicontinental shelf separated by the mainland, mentary prism (1A) and with a structural edge (1B), in
e.g. Adventure Bank (Colantoni et al., 1985). A similar the structural highs of the Monti di Palermo offshore and
variability of continental shelves, as that we illustrated re- around the main rocky headlands (Capo San Vito, Monte
spect to the NW Sicily offshore, has been detected by Catalfano); b) type 2, depositional shelves, in the Castel-
Corradi et al., (1984), along the Ligurian Sea margin. lammare, Palermo and Termini Imerese gulfs, with a
regular seaward deepening of the substrate (2A) and
6.3. Geological evolution with a substrate uplift at the shelf break (2B).
The trend to tectonic uplift recorded along the
A general tectonic uplift during the Pleistocene,
margin, documented by already described stratigraphic together with the episodic alternation of extensional and
relationships and in agreement with the outcrop alti- compressional events, often with strike-slip component,
tudes of paleo-shorelines along the coast, seems to is responsible for the thickness and facies variation and
start with the Ionian (middle Pleistocene). Previously, geomorphological features, both onland, where residual
the sea recorded an episode of deepening that has al- Pleistocene marine deposits today outcrops, and in the
lowed transgression during the Calabrian in a large area continental shelf, where most of the depositional se-
of the north-western Sicily, where now a neritic succes- quences developed and are now recognized.
sion some tens of meters thick outcrops, discordant on
a pre Calabrian tightly deformed substrate (Ruggeri, As well tectonic activity exerted a control on the
1978). The deposition of this succession marks the be- geomorphological features of the present day coastal
ginning of the formation of the continental shelf in areas and shelf-slope system (e.g. pockmarks and
northwestern Sicily margin, which, by the end of the Ca- mounds) as well as for the submarine canyons and the
labrian, under the influence of glacioeustatic fluctuations mass failure processes.
and slow uplift, produced a frontal accretion of the mar-
gin of some km (<10 km). AKNOWLEDGMENTS
The recorded deepening of the margin at the be- We wish to acknowledge the Italian National Re-
ginning of the Calabrian and the subsequent uplift, search Projects MaGIC (Marine Geological Hazard along
which produced the emersion of the Calabrian portion of
the continental shelf, now outcropping up to about 100