ALPINE AND MEDITERRANEAN QUATERNARY 25(2) 2012 MANUSCRIPT IN PRESS AMQ 25(2) 2012 Available online http://amq.aiqua.it ISSN (print): 2279-7327, ISSN (online): 2279-7335 Alpine and Mediterranean Quaternary, 25 (2), 2012, 141 - 155 VARIABILITY OF DEPOSITIONAL SETTING ALONG THE NORTH-WESTERN SICILY CONTINENTAL SHELF (ITALY) DURING LATE QUATERNARY: EFFECTS OF SEA LEVEL CHANGES AND TECTONIC EVOLUTION Attilio Sulli 1 , Mauro Agate 1 , Maria Mancuso 2 , Fabrizio Pepe 1 , Valentina Pennino 1 , Sabrina Polizzi 1 , Valeria Lo Presti 1 , Francesco Gargano 1 , Francesco Interbartolo 1 1 Dipartimento di Scienze della Terra e del Mare - Università di Palermo, Palermo, Italy 2 Istituto per l’Ambiente Marino Costiero, CNR, Napoli, Italy Corresponding author: Attilio Sulli <attilio.sulli@unipa.it> ABSTRACT: The geological, geomorphological and sedimentological features of the north-western Sicily continental shelf are here illustrated with the aim to propose a geological model able to explain the Neogene-Quaternary evolution of the Sicilian continental mar- gin 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 proc- esses 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 regular 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 tectonic 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 The continental shelf is a shallow marine area, less than 200 m deep on average with low inclination (less than 1-2°), surrounding almost all the continental plates. It extends from the external edge of the inshore (submerged beach) until the sudden and significant increase in the inclination of the seabed, which indi- cates the beginning of the continental slope, character- ized by much higher values, up to 10°. In this area of "transition" subaerial and submarine processes interact to determine the geological and environmental evolu- tion. It can also record considerably the effects of an- thropogenic pollution linked to navigation, mining and other productive activities along the coast. The knowledge on continental shelves have in- creased in recent decades thanks to the investigations on mineral resources or hydrocarbons or features of seabed and substrate on which to lay cables, pipelines and platforms. Even the research aimed to fishing and conservation of marine protected areas have acquired a wealth of morphologic, stratigraphic, sedimentologi- cal and structural data. The characteristic feature of the continental shelf is to be periodically flooded by the sea alternatively with periods of subaerial exposure, so landscape, envi- ronment and physical-chemical conditions change here dramatically and frequently, at least at the scale of geological time. According to the most recent recon- structions (Imbrie et al., 1984; Martinson et al., 1987; Williams et al., 1988) exposition and flooding phases have occurred all over the world with periodicity of 150- 200 ky during the last million years. The continental shelf is thus a highly dynamic environment where stud- ies on the effects of subaerial and submarine proc- esses are essential for a correct reconstruction of the most recent geological evolution. In addition to eustatic and global climatic proc- esses, regional factors, as tectonic processes and nature of sedimentary supply, affect the geological evolution of the continental shelf. Sedimentation along the shelves is dominated by sand deposition together with organogenic carbonates and marine fossils- bearing pelites, in different percentages depending on the climatic zones, the prevailing type of coastline (high or low) and the presence or absence of large river mouths, as well as the distance from coast and the water depth. The activity of benthic organisms and of various types of traction currents (waves, tides, coastal currents, etc.) characterizes the sediments that