Page 1 - Sulli_eall_2012

Available online http:/amq.aiqua.it
ISSN (print): 2279-7327, ISSN (online): 2279-7335

Alpine and Mediterranean Quaternary, 25 (2), 2012, 141-156

VARIABILITY OF DEPOSITIONAL SETTING ALONG THE NORTH-WESTERN
SICILY CONTINENTAL SHELF (ITALY) DURING LATE QUATERNARY:
EFFECTS OF SEA LEVEL CHANGES AND TECTONIC EVOLUTION

Attilio Sulli1, Mauro Agate1, Maria Mancuso2, Fabrizio Pepe1, Valentina Pennino1,
Sabrina Polizzi1, Valeria Lo Presti1, Francesco Gargano1, Francesco Interbartolo1

1 Dipartimento di Scienze della Terra e del Mare - Università di Palermo, Italy
2 Istituto per l’Ambiente Marino Costiero, CNR, Napoli, Italy
Corresponding author: A. Sulli <attilio.sulli@unipa.it>

ABSTRACT: The geological, geomorphological and sedimentological features of the north-western Sicily continental shelf are here illus-
trated with the aim to propose a geological model able to explain the Neogene-Quaternary evolution of the Sicilian continental margin in
the context of the central Mediterranean region.
Above the continental shelf and upper slope the sedimentary succession, showing along the different sectors of the margin considerably
variable internal geometry and stratigraphic relationships with the underlying units, is interpreted as a IV order depositional sequence
(Late Quaternary Depositional Sequence, LQDS) deposited during the last eustatic change (last 125 ky). The lower boundary of the
LQDS is represented by a subaerial erosional surface formed during the last eustatic sea level fall ended in the LGM (20-18 ka). This
unconformity lies above a seaward dipping Pleistocene succession whose depositional architecture is in turn controlled by Quaternary
eustatic sea-level fluctuations.
A dense dataset of morphobathymetric and high resolution seismic data allowed to recognize along the continental shelf to bathyal plain
system different types of continental shelf with different stratigraphic and morphostructural settings, associated to both large-scale pro-
cesses and specific factors related to more local control: a) predominantly rocky shelves, both accompanied by a moderate frontal sedi-
mentary prism and with a structural edge, in the structural highs of the Monti di Palermo offshore and around the main rocky headlands
(Capo San Vito, Monte Catalfano); b) depositional shelves, in the Castellammare, Palermo and Termini Imerese gulfs, both with a regu-
lar seaward deepening of the substrate and with a substrate uplift at the shelf break.
We confirm that depositional sequences in this margin are the result of the interaction between sea level changes and sedimentation, but
demonstrate that the tectonic activity has played a key role, not only in the creation of different types of continental shelves, but also to
determine the different characters of each sequence in different areas.
The general tectonic uplift during the Pleistocene, together with the episodic alternation of extensional and compressional events, often
with strike-slip component, is responsible for the thickness and facies variation both onland, where residual Pleistocene marine deposits
today outcrops, and in the continental shelf, where most of the depositional sequences developed and are now recognized. As well tec-
tonic activity exerted a control on the geomorphological features (e.g. pockmarks and mounds) of the present day coastal areas and
shelf-slope system, as well as for the submarine canyons and the mass failure processes.

Keywords: continental shelf, sequence stratigraphy, Northern Sicily continental margin, morphobathymetry, neotectonics.

1. INTRODUCTION and platforms. Even the research aimed to fishing and
conservation of marine protected areas have acquired a
The continental shelf is a shallow marine area, wealth of morphologic, stratigraphic, sedimentological
less than 200 m deep on average with low inclination and structural data.
(less than 1-2°), surrounding almost all the continental
plates. It extends from the external edge of the inshore The characteristic feature of the continental shelf
(submerged beach) until the sudden and significant in- is to be periodically flooded by the sea alternatively with
crease in the inclination of the seabed, which indicates periods of subaerial exposure, so landscape, environ-
the beginning of the continental slope, characterized by ment and physical-chemical conditions change here
much higher values, up to 10°. In this area of "transition" dramatically and frequently, at least at the scale of geo-
subaerial and submarine processes interact to deter- logical time. According to the most recent reconstruc-
mine the geological and environmental evolution. It can tions (Imbrie et al., 1984; Martinson et al., 1987; Wil-
also record considerably the effects of anthropogenic liams et al., 1988) exposition and flooding phases have
pollution linked to navigation, mining and other produc- occurred all over the world with periodicity of 150-200 ky
tive activities along the coast. during the last million years. The continental shelf is
thus a highly dynamic environment where studies on the
The knowledge on continental shelves have in- effects of subaerial and submarine processes are es-
creased in recent decades thanks to the investigations sential for a correct reconstruction of the most recent
on mineral resources or hydrocarbons or features of geological evolution.
seabed and substrate on which to lay cables, pipelines
In addition to eustatic and global climatic process-