Search

We illustrate the tectono-sedimentary evolution of a Jurassic-Cretaceous intraplatform basin in a fold and thrust belt present setting (Cala Rossa basin). Detailed stratigraphy and facies analysis of Upper Triassic-Eocene successions outcropping in the Palermo Mts (NW Sicily), integrated with structural analysis, restoration and basin analysis, led to recognize and describe into the intraplatform basin the proximal and distal depositional areas respect to the bordered carbonate platform sectors. Carbonate platform was characterized by a rimmed reef growing with progradational trends towards the basin, as suggested by the several reworked shallow-water materials interlayered into the deep-water succession. More, the occurrence of thick resedimented breccia levels into the deep-water succession suggests the time and the characters of synsedimentary tectonics occurred during the Late Jurassic. The study sections, involved in the building processes of the Sicilian fold and thrust belt, were restored in order to obtain the original width of the Cala Rossa basin, useful to reconstruct the original geometries and opening mechanisms of the basin. Basin analysis allowed reconstructing the subsidence history of three sectors with different paleobathymetry, evidencing the role exerted by tectonics in the evolution of the narrow Cala Rossa basin. In our interpretation, a transtensional dextral Lower Jurassic fault system, WNW-ESE (present-day) oriented, has activated a wedge shaped pull-apart basin. In the frame of the geodynamic evolution of the Southern Tethyan rifted continental margin, the Cala Rossa basin could have been affected by Jurassic transtensional faults related to the lateral westward motion of Africa relative to Europe.

The submerged sill in the Strait of Messina, which is located today at a minimum depth of 81 m below sea level (bsl), represents the only land connection between Sicily and mainland Italy (and thus Europe) during the last lowstand when the sea level locally stood at about 126 m bsl. Today, the sea crossing to Sicily, although it is less than 4 km at the narrowest point, faces hazardous sea conditions, made famous by the myth of Scylla and Charybdis. Through a multidisciplinary research project, we document the timing and mode of emergence of this land connection during the last 40 kyr. The integrated analysis takes into consideration morphobathymetric and lithological data, and relative sea-level change (both isostatic and tectonic), resulting in the hypothesis that a continental land bridge lasted for at least 500 years between 21.5 and 20 cal ka BP. The emergence may have occurred over an even longer time span if one allows for seafloor erosion by marine currents that have lowered the seabed since the Last Glacial Maximum (LGM). Modelling of palaeotidal velocities shows that sea crossings when sea level was lower than present would have faced even stronger and more hazardous sea currents than today, supporting the hypothesis that earliest human entry into Sicily most probably took place on foot during the period when the sill emerged as dry land. This hypothesis is compared with an analysis of Pleistocene vertebrate faunas in Sicily and mainland Italy, including a new radiocarbon date on bone collagen of an Equus hydruntinus specimen from Grotta di San Teodoro (23–21 cal ka BP), the dispersal abilities of the various animal species involved, particularly their swimming abilities, and the Palaeolithic archaeological record, all of which support the hypothesis of a relatively late land-based colonization of Sicily by Homo sapiens.

A description of the stratigraphic setting and tectonic evolution of the Late Neogene Ciminna basin (Northern Sicily)

Backthrusting, nappe refolding, and normal faulting frequently characterize late collisional stage of an orogen. Shortening driven by backthrusting is widely reported in the Alpine orogen, and it has been proposed to be responsible for the increase of subsidence. Moreover delamination and backthrusting has been considered as related to subcritical condition of a Coulomb-type accretional wedge (Torres Carbonell et al., 2011). The Sicilian Fold and Thrust Belt (SFTB) was characterized by a three-stage evolution during the last 15 My: two main shortening events generated and developed at different structural levels (shallow- and deep-seated thrusts in thinskinned thrust-model) and different time intervals, involving mainly the Meso-Cenozoic carbonate units of the ancient African passive continental margin, followed by a more recent thick-skinned thrust-model involving the Plio-Pleistiocene deposits in the frontal area as well as the crystalline basement in the internal sector of the chain. We investigated the northern Sicily continental margin, by using differently-penetrative seismic reflection data, including a deep crustal profile, calibrated with detailed field surveys and borehole data. On the whole, the tectonic edifice appears to be interested, both offshore and onshore, by a peculiar structural style that can be interpreted as a triangle zone bounded, on the southern side by N-dipping high-angle transpressional faults (e.g. Busambra fault), mainly Early Pliocene to Early Pleistocene in age, and on its northern side, by high-angle S-dipping thrusts (e.g. Kumeta fault), deeply connected with a low-angle décollement layer. In the outer sector of the SFTB, double-verging structures (with NW and SE-tectonic transport) have been described for the Plio-Pleistocene evolution of the Gela Thrust System. The southern Tyrrhenian region is also interested by normal faulting and subsidence (e.g. Cefalù basin), delamination processes, and widespread deep seismicity. A late Miocene-Quaternary northern migration of the plate margin producing opposite-verging structures is reported in the northern Africa plate boundary (e.g. NW Algeria Neogene margin; Mauffret, 2007). A plate boundary reorganization during the latest 0.8–0.5 My with the development of backthrusts have been documented in the Mediterranean region (Goes et al., 2004). Our hypothesis is that the most recent tectonic processes in the study region are representative of a late collisional stage in the northern Sicily mountain building and at a larger scale could be a precursor of a change in the subduction polarity in the central belt of Mediterranean, as a consequence of the ongoing collision of the African promontory with the thinned continental to oceanic sectors (Algerian and Tyrrhenian basins) of the European plate.

We present a 1:25.000 scale geological map of the Kumeta-Pizzuta ridge in north western Sicily (Italy), which was achieved by integrating stratigraphic, structural and geophysical data. In this area the tectonic edifice results from the piling-up of deep water-, carbonate platform- and pelagic platformderived tectonic units (Imerese and Sicilide, Panormide and Trapanese domains respectively) originated by deformations of former southern Tethyan continental margin. The structural setting shows interference of subsequent tectonic events, different type of structural styles, and different-scale deformational patterns. Early overthrust of the Imerese on the Trapanese units (since late Serravallian) was followed by wedging at depth of the Trapanese units (after Tortonian). The wedging implied re-embrication and shortening into the overlying Imerese Units and produced main folding and compressive to transpressive structures along the Kumeta-Pizzuta Ridge. Seismic reflection profiles image the main E-W trending anticlines have been offset by high angle reverse to transpressive faults that merge at depth with low angle, regionally widespread, flat decollement surfaces that show, in this sector, a northward tectonic transport. This setting supports backthrusting along transpressional faults in the study area, ruling-out that the Kumeta ridge is a positive flower structure related to a near-vertical deep, crustal, shear zone as formerly suggested

Foreland Basin System tettono-sedimentary evolution along the Sicilian Fold and Thrust Belt

Since the 1970s, paleomagnetic data collected in Sicily have documented large magnitude clockwise (CW) rotations around vertical axis with respect to Africa and the Hyblean foreland. Many Authors argued that rotations arise from rotational thrusting of large coherent nappes coinciding with paleogeographic units. In the forward thrust propagation process, each nappe rotates the overlying nappe stack. This would explain the stepwise decrease of rotation magnitudes from the internal Panormide unit (90°-140°) to the external Saccense unit, yielding no rotation. However, other Authors later proposed that rotations of Sicily are the consequence of dextral shear occurring since late Miocene times along EW to NW-SE strike-slip faults. To understand the tectonics responsible of paleomagnetic rotations in Sicily, we paleomagnetically investigated 29 sites and a stratigraphic section from Meso-Cenozoic sediments belonging to the Imerese and Trapanese successions exposed in the Piana degli Albanesi area, Mt. Kumeta, and Rocca Busambra. In the study area the fold and thrust belt is characterized by the occurrence of two main sets of subsequent tectonic structures: 1) the early thrusts, producing imbricate-fan and duplex since early Tortonian (deep-water Imerese Units thrust over carbonate-platform Trapanese units); 2) the superimposed wedging at depth of carbonate platform units (since late Tortonian), that produced the most striking (and studied) structural highs of Kumeta and Busambra ridges, bounded by transpressive faults. In order to test the effect of the latter faults on the cumulated CW rotation, we collected data along several transects perpendicular to both Kumeta and Busambra ridges. In fact, rotations are expected to diminish progressively moving away from faults located at the northern ridge edges, in a way that is related to fault offset. The main results of our study are as follows: 1. Six new sites (and one site from previous study) show that the Imerese unit rotated ≈130°, similarly to the Panormide unit at the Monti di Palermo. This evidence requires updated discussion on the tectonic and paleogeographic relations between the Panormide and Imerese domains. 2. At Mt. Kumeta the rotations are effectively greater (120°) along the dextral fault plane, but they decrease to 80° (normal value of the Trapanese unit) at only 300-400 m from the fault. Thus we calculate that the lateral offset of the Kumeta transpressive fault is definitely less than 1 km. 3. At both Mt. Kumeta and Rocca Busambra, rotations from Scaglia sites surprisingly increase moving southward (i.e. far from fault). This suggests a differential rotational and tectonic behavior of the Scaglia with respect to the underlying carbonate backbones of the Trapanese ridges. As a conclusion, paleomagnetic rotations in Sicily are almost entirely due to thrust tectonics, while transpressive fault activity induced local rotations that fade out at only few hundreds of meters from fault planes.

During the Messinian the inherited paleo-topography conditioned the depositional environments of the Mediterranean region, already strongly influenced by the effects of the salinity crisis, mainly in the central region, where seabed at that time is expected to be very uneven and shallower than Western and Eastern Mediterranean. Indeed in this area as from 15 Ma the Sicilian Fold and Thrust Belt (SFTB) was originating, characterized by a multi-stage evolution: two main shortening events generated and developed at different structural levels (shallow- and deep-seated thrusts in thin-skinned thrust-model) and at different time intervals, involving mainly the Meso-Cenozoic carbonate units of the ancient African passive continental margin, followed by a more recent thick-skinned thrusting that involved the Plio-Pleistiocene deposits in the frontal area, as well as the crystalline basement in the internal sector of the chain. Just in the Messinian time interval along the internal sectors of this edifice the transition from shallow to deep seated tectonics was recorded. On top of the SFTB different types of basins originated progressively in response to the shortening wave. Depending on their position and related active processes during the Messinian we can distinguish: intramountain (mainly posttectonic), thrust-top (syn-tectonic), and foreland (pre-tectonic) Messinian basins, with different characters and geometries. Our results are only preliminary and could represent a first approach towards a better understand of the present complex distribution of the different variety of the Messinian sequences. The next step of this study should be the palinspastic restoration of the strongly deformed Messinian successions, in order to reconstruct a more detailed Mediterranean paleogeography

The palinspastic restoration of the Sicilian crustal geological cross section (Catalano et al., 2013) points out two subsequent main thrust (MT1 and MT2) active during the Neogene tectonic evolution as well as the decrease of slip and shortening rate estimated for MT2 with respect to MT1 early main thrust. During orogenic building, syn-tectonic deposits are accumulated inside wedge-top-basin that grow on top of thrust sheets. Sedimentary and stratigraphic features of wedge-top basin change trough time following fold and thrust belt evolution. Neogene-Quaternary syn- tectonic successions (terrigenous, evaporitic, hemipelagic and shallow water deposits) extensively crop-out, in more or less wide wedge-top-basins, above the Sicilian Fold and Thrust Belt (Gugliotta et al., 2014 with references therein). These deposits can be grouped in three main sedimentary successions characterized by basal unconformity surface on deformed substrate (thrust wedge) that, also, represent the depositional interface of coeval wedge-top and foredeep basins: i) middle-late Miocene terrigenous, deep-water succession, accommodated on top of accreted Numidian Flysch nappes; ii) late Miocene deepening upwards succession unconformably covering the inner sector of the FTB constituted by thrusting of Meso-Cenozoic deep-water succession (Sicilide, Imerese and Sicanian Units); iii) Upper Pliocene – Quaternary shallow water succession unconformably covering (in the outer sector of the FTB) a tectonic pile (Gela Thrust System) made by thrusting of the former syn-tectonic succession. Tectono-sedimentary evolution of these basin was controlled by the deepening of the structural levels that were active during fold and thrust belt growth. A crucial change was recorded by the wedge-top depozone during late Pliocene-Pleistocene, when a deeper thrust plain (MT2), cut and thickened the crystalline basement (in the inner sector of the FTB), evolving the thrusting model from thin to thick skinned. As consequence of the involvement of the basement in the Sicilian FTB, and of increased orogenic deep load, the foreland basin system recorded a narrowing of the foredeep: - during late Tortonian – early Pliocene, regional lithofacies distribution accounts for a wide foredeep that included the present day Iblean Plateau and its offshore; - following the involvement of the basement and consequent increased orogenic load, the foredeep narrowed up to present day wideness, confined between the deformed outermost units of the GTS, to the NW, and the outcrop of the carbonate successions of the Iblean foreland, to the SE.

The Map Sheet 1:50.000 595 ”Palermo” includes marine and land areas of the topographic map sheet “Palermo”. The map sheet “Palermo” (Palermo Province) covers a part of the Sicily Fold and Thrust Belt (FTB) which has developed along the plate boundary between Africa and Europe in the Central Mediterranean. The Sicily FTB links the African Maghrebide to the Calabrian arc and Southern Apennines. The FTB and its submerged western and northern extensions are part- ly located between the Sardinia block and the Pelagian-Ionian sector, and partly beneath the central southern Tyrrhenian Sea. In this sector of the Mediterranean area, the main compressional move- ments, after the Paleogene Alpine orogeny, began with the latest Oligocene-Early Miocene counterclockwise rotation of Corsica-Sardinia, believed to represent a volcanic arc, and its collision with the African continental margin. Thrusting oc- curred in connection with the westward subduction of the Adriatic and Ionian lithosphere beneath the Corsica-Sardinia block. Today, a westward subduction is indicated by a North-dipping Benioff zone, as deep as 400 km, west of Calabria and the Apennines, and the related calc- alkaline volcanism in the Eolian Islands. Subduction and thrusting are contempo- raneous with a back arc-type extension in the Tyrrhenian Sea.186 LAND AREAS geomorphoLogy Three different sectors can be distinguished in Sheet 595: 1) the Palermo and Bagheria coastal plains, characterized by several poly- cyclic marine terraces organized in different orders; 2) the isolated carbonate reliefs of Monte Pellegrino and Monte Catalfano; 3) the internal Belmonte Mezzagno highlands and the Oreto and Eleuterio river valleys. The geomorphological evolution of the area has been controlled by strong down-cutting and dismantling processes that have produced both the erosion of thick volumes of mainly Tertiary terrigenous deposits and the exhumation of mainly Mesozoic carbonate rocks. Due to tectonic uplifting, these proces- ses are intensely developed on ”soft rocks “(Numidian Flysch clayey deposits), producing large river valleys with slopes affected by water erosion and surficial landslides (valleys of Fiume Oreto, Fiume Eleuterio and Fiume Milicia); they have, however, considerably slowed down along the blocks of more resistant rock (Mesozoic-Tertiary carbonate units), forming the wide Palermo Mountains. At the present-day, relict (planation surfaces and abandoned valleys), structural (fault/fault-line scarps) and karst (sinkholes and polje) forms occur in the highlan- ds. The geomorphological setting of the coastal areas has been influenced more by significant Quaternary extensional tectonics that originated the drowning of the northern sectors of the Sicilian chain in the Tyrrhenian Sea above which the marine deposition was deposited (Marsala synthem). The uplifting, involving also the lowered blocks, has resulted in the progressive retreat of the sea that gave origin to a succession of marine terraces, Ionian-Latest Pleistocene in age, and fi- nally the emersion of the present-day coastal depressions (Palermo and Bagheria plains). During the Upper Pleistocene to Holocene, the uplifting rates reached values generally lower than 0.1 m/ky. stratIgraphy The carbonate and terrigenous rock facies analysis and stratigraphy led to the recognition of large Paleozoic to Miocene sedimentary bodies pertaining to diffe- rent and separate crustal paleogeographic domains; the former, developed along the African passive continental margin and the adjacent Tethyan ocean. The “Tethyan” successions correspond to the deep clayey carbonate and vol- canoclastic rocks known to have been deposited in the Sicilide Domain. The pas- sive margin rock bodies are shallow water carbonates, deep water carbonates and 187 siliceous carbonates that were deposited in domains, locally known as Panormide, Trapanese and, Imerese. Terrigenous, evaporitic and clastic-carbonate rocks, Miocene to Pleistocene in age, formed during the foredeep evolution of the Sicilian FTB. A detailed stratigraphy of the rock-successions is summarized in the paragraph “Legend of the Palermo Sheet”. Quaternary continental deposits have been mapped as unconformity-bounded stratigraphic units limited by lower and upper unconformities, locally marked by palaeosoils, due to erosion/depositional processes, marine/sub-aerial processes or non-depositional events. Locally, the upper boundaries are the present-day topo- graphic surface. The detection of some unconformities of regional extent allowed us to define several synthems. The Marsala synthem is a Lower Pleistocene body of marine/coastal deposits, with abundant fossils; its lower boundary is a mari- ne erosion surface cutting pre-Quaternary rocks. The Buonfornello-Campofelice synthem is composed of middle Pleistocene marine deposits covering abrasion surfaces above the coastal stepped blocks. The Polisano synthem is made up of aeolian sandstones and sands with intercalations of breccias talus, late Middle Pleistocene in age (OIS 6); its lower boundary is a non-depositional surface at the top of older rocks. Eleuterio and Milicia synthems are made up of Middle-Upper Pleistocene, mainly fluvial, deposits deposited on river terrace surfaces; their lo- wer boundary is a stream erosion surface. The Benincasa synthem includes colluvial Middle-Upper Pleistocene deposits of Qz-sandstones interbedded with stone-line, palaeosoils, Fe-rich layers and no- dular concretions. Its lower boundary is an unconformity above the Buonfornello- Campofelice synthem, the upper one is the base of the Capo Plaia synthem of the present soil. The Barcarello synthem encompasses marine/coastal conglomerates and are- nites, with a rich warm-temperate “Senegal fauna” including Strombus bubonius; it is located on two orders of marine terraces (OISs 5e and 5c or 5a) and laterally passes into welded colluvial deposits whose age is correlated with the OIS 5. The lower boundary of the synthem is a marine abrasion surface, laterally extending to a continental erosion surface; the latter is cutting the Polisano synthem or older rocks. The Raffo Rosso synthem consists of aeolian sandstones and sands, collu- vial or gravitational deposits and thick stratified slope deposits of the last glacial climatic event (OISs 4-2); the lower boundary is a non-depositional surface at the top of the Barcarello synthem or older rocks. The Capo Plaia synthem is made up of coastal to continental deposits of the last glacial climatic event of the end - Holocene age (OISs 2-1); its lower boundary is formed by variously origina- ted erosion or non-depositional surfaces; the upper boundary is the topographic surface.188 struCturaL graIn The Paleozoic to Cenozoic, mainly carbonate sedimentary bodies, developed in different sectors of the African passive continental margin and the adjacent Tethyan ocean and were progressively accreted in a pile of tectonic units and are now exposed to form the Sicilian fold and thrust belt. To define the extension and setting of these bodies versus their internal facies pattern, we individuate them as Structural-Stratigraphic Units (U.S.S.), described as large geological bodies per- taining to original paleogeographic domains from where they were removed and later deformed. These bodies are bounded by clearly mappable tectonic features (faults, thrust, etc.) and each of them is characterized by homogeneous lithologies and similar structural behaviours and settings. The outcropping tectonic edifice, in the “Palermo” Sheet, is composed of se- veral U.S.S., which can be locally subdivided into tectonic units of minor order. These subunits have been mapped on the basis of their tectonic relationships. Some U.S.S. have been identified, starting from the geometrically highest and most internal in the FTB. 1) U.S.S. deriving from the deformation of the Sicilide domain succession: - U.S.S. Tusa-Troina outcropping in the south-eastern sector, overlying the Numidian Flysch deposits. 2) U.S.S. deriving from the deformation of the Imerese domain succession and its overlying numidian flysch basin. The units widely outcrop in the cen- tral and southern sector of the geological sheet where Mesozoic deep water carbonates and their oligo-miocene numidian flysch covers are deformed, with the latter often slightly detached from the carbonate substrate. Among them we distinguished: - U.S.S. Sagana - Belmonte Mezzagno, in the western sector, where we indi- viduated the sub-unit Pizzuta-S.Cristina; - U.S.S. Monte Cane-San Calogero, in the eastern sector, subdivided into a) the subunit Monte Cane-S. Onofrio, overlying b) the subunit Bizolelli; 3) U.S.S. deriving from the deformation of the Panormide Domain. The U.S.S. consists of Meso-Cenozoic shelf to pelagic carbonates and the often detached nu- midian flysch cover, pertaining to the U.S.S. M. Gallo-M. Palmeto, forming the margin of the Panormide Platform. It outcrops only at Monte Pellegrino (subunit Pellegrino). 4) U.S.S. deriving from the deformation of the Trapanese domain. It is recognizable only in the seismic profile crossing the eastern sector where it is overlain by the U.S.S. Sagana - Belmonte Mezzagno. Southwards, it oucrops at Monte Balatelle (U.S.S. Kumeta-Balatelle).189 Structural evolution The tectonic edifice outcropping and buried beneath the area of the Palermo Sheet is the result of several deformational events that have taken place since the Triassic, deforming complexly the sedimentary successions deposited during the Mesozoic-Pleistocene. After the detachment from their crystalline basement the original sedimentary bodies were progressively accreted in a pile of tectonic units now exposed in the Sicilian chain. Two main events have occurred during the Miocene and Pleistocene time interval. They are respectively characterized by compression and transpression. Contraction originally involved the Tethyan domains and the internal domains of the continental margin, whose deep water meso-cenozoic carbonates formed the structurally highest tectonic units in the chain. The occurrence of intrastratal decollement originated duplex geometries. Since the Messinian, the deformation moved at depth, progressively involving the carbonate platform rock bodies in large E-W antiforms that were successively (during Late Pliocene) folded by NE- SW structures. The transpressional event is proved by NNW-SSE and NE-SW transcurrent and transpressive structures (dextral); it involves the deep-seated car- bonate platform-forming fold structures and severe uplifting that induces reimbri- cation in the overlying Imerese deep-water units. This transpressive event accom- panies the paleomagnetically evidenced thrust rotations between the Late Miocene and the Early Pleistocene. An abrupt change in the tectonic transport direction of the two compressional structure systems is explained taking into account the 120° clockwise rotations based on the paleomagnetic results of ChanneL et alii (1980, 1990); speranza et alii (2000). As a consequence the present day outcropping structural attitude of the structures (and consequently of the deformation fields) do not coincide with the original trends. The compressional and traspressional structures are down faulted northwards by the extensional tectonics. MARINE AREAS In the marine areas, we distinguished different morphological environments, from beaches through the offshore (inner shelf), to the outer shelf and upper slope where two confined slope basins (Palermo and Termini basins, separated by the Monte Catalfano salient) represent the south-western margin of the large Cefalù basin. The substrate of these basins is represented by the Sicilian FTB tectonic units and their syn- and post-orogenic covers. The area shows a lateral variation from the rocky shores, in front of Monte Pellegrino and Monte Catalfano and in the eastern sector, to the beaches mainly in the central sector.190 Important physiographic changes, as shelf width and gradient and different coast orientations, characterise the continental shelf and slope and influence the hydrodynamic processes (wave activity and shelf current patterns). The continental shelf reaches 250 km2 and shows width values ranging from 1.5 km in the Capo Zafferano offshore to 8,0 km in the gulf of Termini, whereas gradient values range between 1° and 8°. The continental shelf has been subdi- vided into an inner infralittoral domain down to a 30 - 35 m water depth, which is characterized by an abrasion platform at different depths, and the outer shelf domain extends to the shelf edge. The shelf edge, which is both depositional and erosional, located at water depths between 120 m and 140 m, rises to lower depths at the canyon heads. Dominant morphological features along the continental slope are the submari- ne erosive conduits, locally interesting also the continental shelf. The heads of the conduits are characterised by severe episodes of retrogressive failure and incised by small gullies. Some (the Oreto and Eleuterio canyons) are directly linked to rivers and were connected during the last glacial maximum through incised val- leys, now buried by transgressive to highstand deposits. In the central sector of the Gulf of Palermo, we pinpointed almost three pockmarks, depressions tens of meters deep, originating from escaping fluids, while in the western sector of the gulf the same phenomena caused the occurrence of isolated or aligned, outcrop- ping or buried mounds. Finally anthropic features largely characterize the seabottom mainly in the inner shelf. seIsmostratIgraphy and stratIgraphIC settIng The buried sedimentary succession has been investigated by means of a close grid of single and multichannel seismic lines. On the whole, three seismic units (S, C and A) have been distinguished. The S seismic unit represents the offshore prolongation of the Meso-Cenozoic units of the Sicilian FTB and their syn- and post-orogenic cover. They are ge- nerally topped by a pronounced, erosive unconformity, correlated to the exten- sive Messinian horizon, generated during the last phases of the Mediterranean Salinity Crisis (5.5 Ma), and covered by a transparent seismic unit representing the Globigerina - bearing pelagic chalk (Trubi) and the Upper (?) Pliocene slope to shelfal deposits. The C seismic unit is represented by a prograding succession of 4° to 7° dip- ping horizons, which have been correlated with the regressive upper Pliocene- Pleistocene deposits, topped by the regional wide, erosional truncation related to the last glacioeustatic sea level fall, correlated with the δ18 O isotopic stage 2. The A seismic unit corresponds to the Late Pleistocene to Holocene 191 depositional sequence (SDTQ) with sigmoidal to tabular geometry; the deposi- tional sequence consists of a Falling Stage and Lowstand Systems Tracts with a progadational pattern controlling a relevant out-building of the shelf margin and a sedimentary wedge, of variable thickness, made up of the Transgressive (TST) and the Highstand (HST) Systems Tracts. The TST, developed during the Holocene sea level rise, shows a retrograda- tional stacking pattern, while the HST, deposited during the last 6 ka b.P., shows aggradational to faintly progradational geometries, related to the development of a littoral depositional system. Along the upper slope, turbiditic systems, characterized by erosive conduits and scattered mass wasting, developed extensively during the Late Pleistocene to Holocene. Surficial sediments of the continental shelf and slope The continental shelf and slope of the Palermo sheet are veneered with uncon- solidated, late Holocene in age, clastic and biogenic carbonate (Palermo gulf) and in second order, lithoclastic (Termini gulf) sediments. Deposits are composed of sands, relict Pleistocene and older carbonate parti- cles, abundant biogenic carbonate granules and algal-coated grains. In the outer shelf and upper slope, deposits are predominantly fine to very fine grained (silts and silty clays). The inner shelf is veneered by a mixture of gravel (rarely), coarse to fine sands, silts and clays, showing a general trend of decrea- sing size in a general seaward direction. From the sedimentary and the morphological features, four different depo- sitional systems have been distinguished: foreshore depositional systems, inner shelf depositional systems, outer shelf depositional systems and upper slope de- positional systems, mapped as g8 , g19 , g21 , m2 respectively. The systems are laterally gradational and linked by a variety of sedimentary processes. Shallow marine environments (up to a 50 m water depth) are generally characterized by biogenic sediments while terrigenous and carbonate clastic sedi- ments supplied by rivers or coastal erosion locally prevail. The most important facies of the infralittoral domain consists of Posidonia oceanica and Cymodocea nodosa meadows, which extensively cover the rocky substrate or the sandy floors the former and the muddy floors the latter. teCtonIC evoLutIon of the offshore areas The present day structural setting reconstructed in the Palermo sheet marine sectors appears the same as the tectonic edifice depicted on the mainland: it has 192 been interpreted as a consequence of the complex Neogene to Quaternary tectonic evolution. The compressive tectonics, responsible for the wedging of the present day submerged thrust sheets, developed during the Late Miocene span interval. This event was followed by transpressive tectonics that faulted and folded the Late Neogene to Pliocene infill by activation of high-angle, deep faults. During the Pleistocene, extensional tectonics accounted for opening and subsidence of structural lows. Present day active tectonics is still going on, as documented by compressive- transpressive focal mechanisms of shallow to deep, low amplitude earthquakes occurring along the offshore between the Sicilian coast and Ustica Island. A few middle-late Pleistocene marine terraces, outcropping along the coast at different levels, suggest a prolonged, faintly tectonic uplift. On the whole, the Plio-Quaternary geological evolution of the offshore area appears to be constrained by a strong interaction between eustatic sea level chan- ges, sediment supply and tectonics, recorded by strain features and enhanced un- conformities crossing the basin fill.

The exploitation of economic resources in marine environment and the assessment of natural hazards press a greater knowledge of the sea floor geology. Since the Structural Model of Italy was published in the 1991 by the CNR, new data have been collected concerning the marine geology of the sea floor surrounding Italy, also by means of up to date technologies (digital seismics, SBP Chirp, Multibeam). Data collected during the last decades in the frame of research programs as CROP MARE, CARG, morpho-bathymetric survey of the Tyrrhenian Sea, MAGIC, allow investigating the submerged geological structures with different temporal and spatial resolution. As consequence, at present marine geologists can draw geological maps where different geological features and related tectonic structures can be highlighted: 1) the depth of the Moho discontinuity; 2) the depth of the carbonate platform top; 3) the depth of the Messinian unconformity and the thickness of the Plio-Quaternary basin infill; 4) the Late Quaternary depositional sequence; 5) the main morpho-structural features (volcanoes, canyons, slides and slumps). Geological maps containing all of this information allow to define the submerged stratigraphic and structural setting and to reconstruct the geological evolution of the Italian sea floors, helping in to assess the marine geological hazard. The criteria for representation must be chosen so as to facilitate the correlation with the adjacent emerged areas. A particular attention will be paid to the late orogeny structures that controlled the Quaternary morphogenesis and mostly responsible for the present day morpho-structural setting of the Italian sea floor as well as the seismicity of this region. In this communication, a few geological map examples coming from the Sicily offshore will be shown to debate the scale and the most appropriate methodologies to be used for the representation of a new structural model of the Italian sea floor.

The 594-585 ”Partinico-Mondello” Map Sheet 1:50.000 includes marine and land areas of the topographic map sheet “Partinico” and “Mondello”. The map sheet “Partinico-Mondello” (Palermo Province) covers a part of the Sicily Fold and Thrust Belt (FTB) which has developed along the plate boundary between Africa and Europe in the central Mediterranean. The Sicily FTB links the African Maghrebides to the Calabrian arc and the Southern Apennines. The fTB and its submerged western and northern exten- sions are partly located between the Sardinia block and the Pelagian-Ionian sec- tor, and partly beneath the central southern Tyrrhenian Sea. In this sector of the Mediterranean area, the main compressional movements, after the Paleogene Alpine orogeny, began with the latest Oligocene-Early Mio- cene counterclockwise rotation of Corsica-Sardinia, believed to represent a volca- nic arc, and its collision with the African continental margin. Thrusting occurred in connection with the westward subduction of the Adriatic and Ionian lithosphere beneath the Corsica-Sardinia block. Today, a westward subduction is indicated by a North-dipping Benioff zone, as deep as 400 km, west of Calabria and the Apennines, and the related calc- alkaline volcanism in the Eolian Islands. Subduction and thrusting are contempo- raneous with a back arc-type extension in the Tyrrhenian Sea. 237lAND AREAS geomorphology The geomorphological evolution of the studied area has been controlled by strong down-cutting and dismantling processes that have produced both the ero- sion of thick volumes of very recent terrigenous deposits and the exhumation of older rocks. Due to tectonic uplifting, these deepening processes are developed intensively on “soft rocks” (Numidian fysch clayey deposits), producing large river valleys whose slopes are affected by water erosion and surfcial landslides (Nocella and Oreto rivers); erosion has slowed down considerably along the more resistant Mesozoic-Tertiary carbonate rock units of the wide ranges of the Palermo Mountains. In the present-day, relicted planation surfaces and abandoned valleys, fault/fault-line scarps and karst “dolines” and “poljes” occur in the mountainous areas. On the other hand, the geomorphological setting of the coastal areas has been infuenced by important Quaternary extensional tectonics that were at the origin of the lowering of the northern sectors of the Sicilian chain submerged by the Tyrrhenian Sea and invaded by coastal marine depositions (Marsala synthem). Uplifting, involving also the subsided blocks, together with sea level variations, has led to the progressive withdrawal of the sea that originated a succession of marine terraces, Tarantian-Latest Pleistocene in age, followed by the emersion of the present-day coastal depressions (Partinico, Carini and Palermo plains). Du- ring the Upper Pleistocene to Holocene, the uplifting rates reach values between about 0.08 and 0,15 m/kyr. stratigraphy The carbonate and terrigenous rock facies analysis and stratigraphy has led to the reconaissance of large Paleozoic to Miocene sedimentary units pertaining to different crustal paleogeographic domains; the former developed along the Pela- gian (African) passive continental margin and the adjacent Tethyan Ocean. The “Tethyan” successions correspond to the deep sea, clayey carbonate and volcanoclastic rocks known to have been deposited in the Sicilide Domain. The passive continental margin, rock units are Meso-Cenozoic shallow water carbo- nates, deep water carbonates and siliceous rocks that were deposited in some domains, locally known as Panormide, Trapanese and Imerese. The terrigenous evaporitic and clastic-carbonate rocks, Miocene to Pleistocene in age, formed during the foredeep evolution of the Sicilian fTB. A detailed stratigraphy of the rock-successions is summarized in the next paragraph (see map Legend of the sheet). 238Quaternary continental (mostly) and marine deposits have been mapped as unconformity-bounded, stratigraphic units limited by lower and upper uncon- formity surfaces, locally marked by palaeosols, due to erosion/depositional phe- nomena, marine/sub-aerial processes or non depositional events. In place, the upper boundary is the present-day topographic surface. The detection of some unconformity surfaces of regional extent allowed us to defne several synthems here described from the older ones. The Marsala synthem is a lower Pleistocene rock unit of marine/coastal deposits, with abundant fossils; its lower boundary is a marine erosion surface cut into pre-Quaternary rocks. The Piana di Parti- nico synthem is made up of marine/coastal deposits located above a number of marine terrace surfaces, related to sea-high, stand phases of the Middle Pleisto- cene (Oxygen Isotope Stages – OISs - 17-7); its lower boundary is a wave cut platform carved into the Marsala synthem or some pre-Quaternary rocks. The Polisano synthem is made up of aeolian sandstones and sands with intercalations of breccia talus, late Middle Pleistocene in age (OIS 6); its lower boundary is a non-depositional surface at the top of the Piana di Partinico synthem or older rocks. The Oreto and Jato synthems are made up of Middle – Upper Pleistocene mainly fuvial deposits located on river terrace surfaces; their lower boundary is a stream erosion surface. The Monreale synthem consists of Middle Pleistoce- ne carbonate speleothems (mainly travertines); its lower boundary is a subaerial erosion surface cut both into the Marsala synthem or into the pre-quaternary rocks. The Barcarello synthem encompasses marine/coastal conglomerates and arenites, with a rich warm-temperate “Senegal fauna” including Strombus bubo- nius; the unit is located above two orders of marine terrace (OISs 5e and 5c or 5a) and laterally passes into welded colluvial deposits whose age is correlated to the oIS 5. The lower boundary of the Barcarello synthem is a marine abrasion surface, laterally extending into a continental erosion surface; the latter cuts the Polisano synthem or older rocks. The Raffo Rosso synthem consists of aeolian sandstones and sands, colluvial or gravitational deposits and thick stratifed slope deposits of the last glacial climatic event (OISs 4-2); the lower boundary is a non- depositional surface located at the top of the Barcarello synthem or older rocks. The capo Plaia synthem is made up of coastal to continental deposits of the last glacial climatic event end – Holocene age (OISs 2-1); it is comprised in the lower boundary, formed by variously originated erosion or non-depositional surfaces and the topographic surface. struCtural grain The geological map has been compiled following stratigraphic and structural criteria, suggested by the CARG rules. Following the carbonate and terrigenous 239facies analysis, already carried out in western Sicily during the eighties and nine- ties, large Paleozoic to Cenozoic sedimentary units were identifed. These bodies, detached from their basement, progressively accreted in a pile of tectonic units and are now exposed in the Sicilian FTB. To defne the extension and setting of the mentioned units versus their internal facies pattern, we have used the term Structural – Stratigraphic units (USS). The USS are bounded by clear mappable tectonic features (faults, thrust surface, etc.) and each one is characterized by ho- mogeneous lithologies and similar structural behaviours and settings. The outcropping tectonic edifce in the “Partinico-Mondello” geological map sheet is formed by some USS that, locally, can be subdivided into tectonic units of minor order mapped on the basis of their tectonic relationships. The following USS have been identifed from the geometrically highest and most internal ones in the “Partinico-Mondeòlo” tectonic edifce: 1) the USS deriving from the deformation of the Imerese Domain and its overlying Numidian fysch basin. The units outcrop in the central southern sector of the geological sheet and are Meso-cenozoic deep water carbonates deformed together with their Oligo-Miocene Numidian fysch cover. The latter is detached from its carbonate substrate. Among them: - USS Meccini; - USS Sagana – Belmonte Mezzagno. The latter has been separated into three subunits based on the occurrence of some décollment surfaces (low and high angle) that put in evidence the deforma- tion (thickening) of the rock succession: a) Cuccio-Saraceno is the highest in the stack; b) Gradara and c) Pizzuta-Santa Cristina are widespread in the southern sectors. The lowest in the stack (the Pizzuta-Santa Cristina unit) overthrusts the Trapanese carbonate Platform units as is clearly shown in the Monte Kumeta Ridge located to the south in the adjacent corleone sheet map. 2) The USS deriving from the deformation of the Panormide Domain con- sist of Meso-cenozoic shelf to pelagic carbonates including their unconformably overlying ,Numidian fysch cover that is, often detached from its substrate. Three main USS have been distinguished and divided, in turn, into subunits: - gallo- Palmeto USS consisting of the Palmeto and gallo subunits - Cozzo di Lupo USS, formed by the shelf to margin carbonates of the Panor- mide Platform, is geometrically underlying the Gallo-Palmeto unit. It has been divided into: the Cala Rossa subunit, occurring in the coastal zone of Terrasini and the Vuturo subunit outcropping in the hilly neighbourhood of Palermo and Torretta. - Pecoraro-colombrina USS. The Unit outcrops in the hills of Monte Pecora- io, Montagna Longa, Monte Colombrina, Cozzo Muletta, Torre Pozzillo near the town of carini. 240Structural evolution The tectonic edifce outcropping and buried beneath the “Partinico-Mondel- lo” map sheet is the result of several deformational events that have taken place since the Triassic, deforming the sedimentary successions deposited during the Mesozoic-Pleistocene in different ways. Two main events took place during the Miocene and Pleistocene time interval. They are respectively characterized by compression and transpression. Contraction, originally involved internal domains of the continental margin whose deep water mesocenozoic carbonates formed the structurally highest tectonic units in the chain. The occurrence of intrastratal decollement gave origin also to the duplex geometries. Since the Messinian, the deformation has gone into depth, progressively involving the carbonate platform rock body in large E-W antiforms that were successively (during Late Pliocene) folded by NE-SW structures. The transpressional event is proved by NNW-SSE and NE-SW transcurrent and transpressive structures (dextral); it involves the deep-seated carbonate platform-forming fold structures and severe uplifting that induces reimbrication in the overlying Imerese deep-water units. This transpres- sive event accompanies the paleomagnetically evidenced thrust rotations between the late Miocene and the Early Pleistocene. An abruplt change in the tectonic transport direction of the two compressional structure systems is explained taking in account the 120° clockwise rotation based on the paleomagnetically results of Channell et alii (1980, 1990); speranza et alii (2000). As a consequence the present day outcropping structural attitude of the structures (and consequently of the deformation felds) do not coincide with the original trends. The compressio- nal and traspressional structures are down faulted northwards by the extensional tectonics. After the detachment from their crystalline basement, the original sedimenta- ry bodies were progressively accreted in a pile of tectonic units now exposed in the Sicilian fold and Thrust Belt. MARINE AREAS The morphological environments from the beach and the foreshore, through to the outer shelf, upper slope and confned slope basin settings are part of the marine area. The area shows a lateral gradation from the fuvially – (i.e. small mountainous rivers) dominated Castellammare Gulf shelf to the sediment – starved Carini Bay. Important physiographic changes, as shelf width and gradient and different coast orientations, characterize the continental shelf and slope and infuence the 241hydrodynamic processes (wave activity and shelf current patterns). The physiographic sectors that have been recognised are, from the West: 1) the eastern parts of the gulf of Castellammare, 2) the shelf of the Carini Bay and 3) the inner shelf of the Mondello Bay. The shelf shows width values ranging from the 8,0 km of the gulf of Castel- lammare to the 10 km of the Carini Bay, whereas gradient values range between 0,4° and 1,35°. The shelf edge, located at water depths between 120 m and 160 m, rises to lower depths at the canyon heads. The continental shelf has been subdivided into an inner infralittoral domain down to a 30 – 35 m water depth and an outer shelf domain, extending to the shelf edge. Off Cape Rama, the seaward boundary between the inner and the outer shelf is marked by a break of slope and by the occurrence of several small wave – cut marine terraces; in the Carini Bay, a paleoshoreline, between a depth of 100 m - 110, divides the shelf into an outer smooth sector and in an inner rough area, where paleoriver valleys occur. Dominant morphological features within the eastern castellammare gulf are the submarine erosive conduits that intercept the dominant littoral drift from the west to the north-west. The heads of the castellammare conduits are characteri- zed by severe episodes of retrogressive failure and incised by small gullies. Ero- sional chutes deeply cut the sedimentary cover of the carini slope. seismostratigraphy and stratigraphiC setting The Plio – Pleistocene buried sedimentary succession has been investigated by means of a close grid of single and multichannel seismic lines. Overall, three seismic units (PL, PQ and STDQ) have been distinguished. The PL seismic unit unconformably overlies a pronounced, erosive unconfor- mity (refector Y) that has been correlated to the extensive Messinian horizon, ge- nerated during the last phases of the Mediterranean Salinity Crisis (5.5 Ma b. P.). The Pl seismic unit has been interpreted as being made up of globigerina – bearing pelagic chalk (Trubi) and the Upper (?) Pliocene slope to shelfal deposits, pertain to the “marnoso arenacea del Belice”. The Pq seismic unit has been correlated with the regressive Pleistocene depo- sits, bounded below to the x horizon, corresponding to the lower boundary of the Marsala synthem and topped by the regional-wide, erosional truncation related to the last glacioeustatic sea level fall, correlable with the δ18 o isotopic stage 2. In the stratigraphic section, transversal to the coastline, the Late Pleistocene to holocene STDq shows a sigmoidal to tabular geometry; the depositional se- quence consists of a falling Stage and a lowstand Systems Tract with a progra- dational pattern controlling a relevant outward-building of the shelf margin and 242a sedimentary wedge, of variable thickness, made up of the Transgressive (TST) and the Highstand (HST) Systems Tracts. The TST, developed during the Holocene sea level rise, shows a retrograda- tional stacking pattern of three small parasequences, well defned in the eastern sectors of the Castellammare shelf but more condensed in the Carini Bay; here, the holocene sea level stillstands have been recorded by three orders of submer- ged paleo-shorelines. The HST, deposited during the last 6 ka b.P., shows aggradational to faintly progradational geometries, related to the development of a deltaic to littoral de- positional system. In the inner continental shelf of the eastern Castellammare Gulf, seismic fa- cies, like “migrating waves” and acoustic wipe – out, suggest sedimentary insta- bility and gas expulsion phenomena. Along the upper slope, an extensive slope to turbiditic system, characterized by erosive conduits and scattered mass wasting deposits, developed during the late Pleistocene to holocene. Surfcial sediments of the continental shelf and slope The continental shelf and slope of the “Partinico – Mondello” sheet are vene- ered with unconsolidated, late Holocene in age, terrigenous and carbonate clastic and biogenic sediments. Deposits are composed of quarzose sands, relictic? Pleistocene and older car- bonate particles, abundant biogenic carbonate granules and algal-coated grains. In the outer shelf and the upper slope seafoors, deposits are predominantly fne to very fne grained (silts and silty clays). The inner shelf seafoors are vene- ered by a mixture of very coarse to fne sands, silts and clays, showing a general trend of decreasing size in a general seaward direction. According to the sedimentary and the morphological features, four different depositional systems have been distinguished: foreshore depositional systems, inner shelf depositional systems, outer shelf depositional systems and upper slope depositional systems, mapped as g8, g19, g21, m2 respectively. The systems are laterally gradational and linked by a variety of sedimentary processes. Shallow marine environments (up to 50 m of water depth) are general- ly characterized, in the Castellammare Gulf, by terrigenous and carbonate clastic sediments supplied by rivers or coastal erosion; in the carini Bay and in the inner shelf of Mondello, biogenic sediments prevail. The most important facies of the infralittoral domain consists of Posidonia oceanica and Cymodocea nodosa meadows that extensively cover the rocky sub- strate or the sandy foors the frst, muddy foors the latter. 243teCtoniC evolution of the offshore areas The present day structural setting reconstructed in the castellammare basin and Palermo salient marine sectors appears correlatable to the tectonic edifce depicted on the mainland: it has been interpreted as a consequence of a complex Neogene to Quaternary tectonic evolution. The compressive tectonics, responsi- ble for the wedging of the present day submerged thrust sheets, developed during the late Miocene span interval. This event was followed by transpressive tecto- nics that faulted and folded the Late Neogene to Pliocene infll by activation of deep, high-angle faults. During the Pleistocene, extensional tectonics accounted for opening and sub- sidence of structural lows. Present day active tectonics are still going on, as documented by compressive- transpressive focal mechanisms of shallow to deep, low amplitude earthquakes occurring along the offshore between the Sicily coast and Ustica Island. A few middle-late Pleistocene marine terraces outcropping along the coast at different levels suggest a prolonged, faintly tectonic uplift. On the whole, the Plio-Quaternary geological evolution of the offshore area appears constrained by a deep interaction between tectonics, eustatic sea level changes and sediment supply, recorded by strain features and enhanced unconfor- mities crossing the basin fll.

The study region is a part of the Sicilian-Maghrebian Fold and Thrust Belt (FTB), a segment of the Alpine collisional belt, recently described as a result of both post-collisional convergence between Africa and Europe and roll-back of the subduction hinge of the Ionian lithosphere. The region (extending in central Sicily from the Madonie Mountains. to the eastern corner of the Iblean-Pelagian foreland through the impressive NE-SW trending Tertiary clastic and evaporitic range of the Caltanissetta trough) is located in an area where the main thrust system disappears beneath a wedge of deformed Neogene deposits. Earlier studies have neglected the importance of the potential target for hydrocarbon opportunities as well the occurrence of carbonate platform rock bodies at a depth and their tectonic relationships with the deepwater carbonate thrust systems. Due to the poorly known structural and stratigraphic characters of the study area some questions arise: - Is there a thrust pile structurally comparable with the western and eastern Sicily tectonic wedge? - Are there carbonate platform units involved in the belt and what is their depth? - Is the clastic and evaporitic Neogene tectonic wedge filling the Caltanissetta trough so thin to be crossed by oil research boreholes? Stratigraphy and mesostructural analyses, accomplished in the last years, in the frame of the Field Mapping CARG Project, provide new data able to constrain the geological cross-sections.The latter are further calibrated by a deep crustal seismic profile (SI.RI.PRO. Project, scientific leader R. Catalano) recently acquired across Sicily, together with refraction seismic, gravimetry and magnetotelluric data. It has strongly improved the knowledge of the deep crustal characters beneath the central Sicily. The recognized deep geometries and the presumed Moho location represent a strong control of the surface geological setting. The results obtained illustrate the foreland forming a steep regional monocline underlying a thickened carbonate thrust wedge to the north and the Gela Nappe to the south, allowing a correlation between outcropping and buried carbonate units, and evidencing the structural relationships between shallow and deep water carbonate units. The reconstruction of the pattern and timing of deformation will be able to propose a kinematic model useful for exploration strategies.

Il Foglio 593 “Castellammare del Golfo” della Carta Geologica d’Italia in scala 1:50.000 è stato realizzato nell’ambito del Progetto CARG con i fondi della Legge 305/89, con una convenzione tra Servizio Geologico Nazionale (ora ISPRA) e la Regione Siciliana. Il Foglio “Castellammare del Golfo” ricopre un settore dell’ estremità nordoccidentale della Sicilia e comprende le aree marine del Golfo del Cofano, della Baia di San Vito e della porzione centro-occidentale del Golfo di Castellammare, e quelle emerse costituite dalla dorsale dei Monti di Capo San Vito, dall’ampio settore collinare di Monte Luziano e Monte Bosco, dal massiccio di Monte Inici e dai pianori della Piana di Castellammare, della Piana di Castelluzzo e della Piana di Sopra (Fig. 1). La carta geologica delle aree emerse è il risultato dell’esecuzione di rilievi originali condotti nelle aree costiere ed in gran parte dell’area continentale cui si aggiungono i contributi della revisione di rilievi effettuati nella penisola di San Vito e resi pubblici precedentemente. L’intera superficie è stata rilevata alla scala 1:10.000 su sezioni topografiche della Carta Tecnica Regionale messa a disposizione dalla Regione Siciliana, Assessorato al Territorio ed Ambiente, che ha fornito anche i rilievi aereofotogrammetrici sui quali sono state condotte le analisi fotogeologiche. Per il rilevamento delle sezioni si è operato secondo quanto prescritto dal Programma Operativo di Lavoro (POL) ed in conformità alle indicazioni del Quaderno n° 1, serie III del S.G.N. Particolare cura e dettaglio sono stati riservati alla mappatura e alla classificazione dei principali prodotti di dissesto geomorfologico che comprendono anche i depositi coerenti interessati da movimenti gravitativi profondi di versante. I depositi pleistocenici sono stati cartografati con particolare attenzione in quanto informazioni essenziali per il controllo e la tutela del territorio, seguendo le complesse norme emanate dal Servizio Geologico Nazionale (ora ISPRA). Oltre ai dati di superficie, i rilievi del Foglio “Castellammare del Golfo” si giovano dei risultati provenienti dall’interpretazione dei dati di sottosuolo, calibrati da pozzi profondi perforati ai margini del Foglio (Trapani 1, Alcamo 1). La porzione sommersa del Foglio 593, estesa all’incirca 460 km2, ricade nel settore centro-occidentale del Golfo di Castellammare, nella piccola baia a nord di San Vito e, ad ovest, nel Golfo del Cofano e comprende aree di piattaforma e di scarpata continentale (Fig. 1). I rilievi geologici marini sono stati eseguiti dai ricercatori del Gruppo di Geologia Marina (responsabile Prof. R. Catalano) del Dipartimento di Geologia e Geodesia dell’Università degli Studi di Palermo, nell’arco del triennio 1999-2002. I rilievi marini sono stati condotti nel rispetto di quanto previsto dal POL coordinato con il Servizio Geologico Nazionale ed utilizzando una carta a scala 1:25.000, costruita sulla base dei dati batimetrici digitali forniti dall’Istituto Idrografico della Marina (I.I.M.) e di rilievi batimetrici inediti raccolti ed elaborati dagli A.A. e validati dall’I.I.M. con comunicazione del 18/03/2003. I rilievi sono stati estesi ad un’area più ampia di quella inclusa nel Foglio, al fine di ricostruire l’assetto delle strutture tettoniche e di definire un quadro stratigrafico omogeneo valido anche per l’adiacente Foglio 594-585 “Partinico-Mondello” di prossima pubblicazione. Dell’area marina del Foglio viene presentata anche una Carta del Sottofondo contenente la stratigrafia sequenziale dei depositi tardo-quaternari e le più importanti morfostrutture sommerse.

Vertical position of sea-level, pointed out by related deposits and morphologies, provide useful markers to estimate tectonic uplift rates. For the Holocene very high uplift rates are misured in the northeast Sicily coast (Antonioli et al., 2009). This study compare vertical tectonic movements and marine geology data in the coastal sector between Capo d’Orlando and Brolo (NE Sicily); tectonic lineaments show different trends both onland (Nigro & Sulli, 1995) and offshore (Nicolich et al.,1982) and also the morphological response follow closely this difference. The geomorphologic survey provided data on Holocene uplift rates. We studied an archaeological ancient quarry of grinding wheels for oil that has been found in the Capo d’Orlando inshore (Scicchitano et al., 2011). They present semi submerged circular holes in Stilo-Capo d’Orlando deposits (Carbone et al., 1998). The tectonic uplift was evaluated as the difference between the observed local paleo-sea level position and the predicted sea-level curve for the same locality (Lambeck et al., 2011). The resulting uplift rates is 0.36 mm/yr (Scicchitano et al., 2011). In this area we studied also the Brolo stack. It is a metamorphic rocks emerging at 450 m from the coastline. The study led to discovery a fossils-bearing conglomerate in protected trays at 3.5 m a.s.l.. Radiocarbon analysis on a gastropod, gave us an age of 4965 years +-70 cal BP. If we compare this data with the predicted local sea level curves (Lambeck et al., 2011), we obtain an uplift rate about 1.5 mm/yr (Lo Presti et al., 2010), which is higher than that calculated in the study of archaeological rest. A detailed study of Brolo sector show us different morphological coastline position of Brolo plain. A picture of the year 1847 shows the coastline about 200 m landward. In Brolo coastal plain we have also found a Spondylus at -6 m b.s.l. We wait for the radiocarbon dating which allows us to have a new uplift rate data. The analysis of marine geology data (Multibeam) evidenced structures connected to different faults systems, such as the submarine canyons that are the continuation of river beds. Multibeam data evidenced also tilted NE-ward submerged surfaces, indicating existing structural movements, interesting only restricted areas. So, very different uplift rates in the Holocene in very close areas distant only about 10 kilometers: both 0.36 mm/yr (Scicchitano et al. 2011) and 1.5 mm/yr (Lo Presti et al. 2010), and morphobathymetric data (tilted surfaces), evidence the important role of active tectonic lineaments. Seismic reflection profiles support this assumption, showing the metamorphic basement strongly dissected by high-angle faults, which at place determines the occurrence of emergent rock bodies (e.g. the Brolo stack). All this suggesting the occurrence of “restricted regions” in the coastal-marine sector with different geological behavior as response to prominent tectonic releasing bands, determining their horizontal and vertical movements.

The north-eastern Sicily coast reflects the effects of Holocene active tectonics associated to subduction system of Ionian crust beneath the Calabrian arc (CAPUTO et alii, 1970; WESTAWAY, 1993, DOGLIONI et alii, 1999). The latter, characterized by a stack of crystalline rock and its sedimentary cover, is the highest structural element in the Sicily chain. The Calabrian arc is a region that records one of the major Quaternary vertical tectonic movement in the whole Mediterranean basin. This uplift, well documented from Last Interglacial, is expressed as vertical variation of the height of the Quaternary marine terraces inner margin that characterize the north-eastern Sicily coast. The uplift can be divided into a "continuous" regional component and in an "episodic"coseismic component (FERRANTI et alii, 2007). The northwest Sicily coast shows as the uplift rates estimated for the Holocene have values greater than those estimated at the same point from Last Interglacial (ANTONIOLI et alii, 2006). At the regional scale it is possible to observe a decrease in uplift rates from Cape Peloro (1.1 mm / year) to Palermo and Capo S. Vito (stable). In north-eastern Sicily, between Capo d'Orlando and Capo Calavà, we studied the Brolo Stack, located in the central part of a small bay along the coast facing Brolo village. This area pertains to the northwestern sector of Peloritani Mountains (western portion of the Calabrian arc), which extend in E-W direction from Messina Straits to S. Agata di Militello village. In particular the tectonic style is characterized by tectonically overlapping bodies, generally dipping toward the northern quadrants. The Brolo coastal area is characterized by a wide coastal alluvial plain fed by two big rivers. On this plain rises a metamorphic salient, a sub-circular cylindrical structure, about 50 m high, placed inshore at 250 m from the coastline. In particular, the Brolo Stack is an outcrop of a residual block of impure, medium grain, marble interspersed with Paleozoic paragneiss and mica schists, which largely outcrops in the hinterland. These lithotypes are the crystalline substrate on which develops the current depositional sequence. The Brolo Stack constitutes a "lentil" of metamorphic rock emerging above the 14-18 m deep seafloor at 450 m from the coastline. The objective of this study is to calculate the potential vertical movements and assume when they could have occurred. To do this a detailed geomorphological subaerial and an underwater survey were conducted, which led to discovery a fossils bearing conglomerate (Fig. 1), in protected trays at 3.5 m from sea level, and well preserved lithophaga holes (Fig. 2) at about 70 cm from sea level. The Brolo stack show a particular morphological feature, different in the emerged and submerged parts (Fig. 3). The emerged portion strikes along the E-W trend for a length of about 43 m, being 29 m wide and about 15 m high. It has a mushroom shape with the submerged part more closely than the emerged, the result of combined physical and chemical processes triggered by both sea level rise and tectonic vertical movements. A system of schistosity gives to the white-to-gray stack an apparent stratification organized in decimetric beds with lying 005/60°. The whole structure is fractured along multiple directions often containing dark poorly consolidated volcanic rock. Large angular blocks are found on the seabed at the base of the submerged cliffs; their collapse is the result of mechanical erosion due to the high energy waves and the schistosity and intensely fractured structure of the rocks. The underwater survey allowed us to recognize little terraces at different depth recognized as structural surfaces. We used radiocarbon analysis on a gastropod found in the marine conglomerate (Fig. 4). We provide an age of 4745 +/- 59, ( 4965 years +-70 cal BP using Calib 5 program, Stuiver et al 2005). Based on the data obtained and morphological considerations, it is difficult to envisage the formation of this beach deposit on the stack if we don’t consider a very different morphological feature, probably more flared with greater lateral continuity and less inclined slopes. If we compare the age of the deposit and the height that was found with the predicted local sea level curves (LAMBECK et alii, 2010, Quaternary International, in press), this is above the curve, indicating a uplift rate about 1.5 mm / years that is higher than that calculated in the same field for last interglacial.

Vertical position of sea-level, related deposits and morphologies (e.g., last interglacial, LIG, 125ka,) provide useful markers to utilize with this purpose (LAMBECK et alii, 2004; FERRANTI et alii, 2006, ANTONIOLI et alii, 2009). Using published (ANTONIOLI et alii, 2006) and new data we provide a review of the northern coast of Sicily uplift rates. The markers used in this study are: terraces inner margin, tidal notches, etc., and, for the last millennia archaeological markers and fossil beaches and vermetid reef. Data on vertical movements calculated for the coastal area developing in the north-Sicilian continental margin indicate that, from East to West, a strong variation of vertical rates of uplift are recognized during both middle-late Pleistocene and Holocene. Uplift rates derived from the LIG markers decrease from east to west from 0.8 mm\yrs (Messina) to 0.2 mm\yrs (Cefalù) The same trend is observed for Holocene markers showing rates still higher (until 2 mm\yrs) than in the LIG. The variations mainly correspond to coastal segments separated by a main regional tectonic feature, the Vulcano-Tindari Fault system (LANZAFAME & BOUSQUET, 1997; BILLI et alii, 2006) with predominantly right-lateral transcurrent (partly extensional and/or contractional) kinematics that dissects transversally the south-western sector of the Calabrian Arc. These structures, which are sub-vertical, cross-cut the whole lithosphere and therefore can act as discontinuities separating crustal blocks characterized by different vertical motion. Here we focus our attention on the eastern sector of the Sicilian northern coast and particularly the area immediately to the west of the Vulcano-Tindari fault system, where several evidences of vertical movements during the Pleistocene-Holocene have been recognized. Here, the occurrence of several oblique and normal fault segments and the alternation of rocks with different competence, that is the Hercynian metamorphic basement, its Meso-Cenozoic carbonate and Oligocene-Miocene terrigenous cover and Pleistocene deltaic sands and gravels (CARBONE et alii, 1998), determine a complex geomorphologic setting. Our analysis was devoted to the coastal sector from Capo d'Orlando to Acquedolci towns, where a well preserved flight of marine terraces occurs. Geomorphologic survey allowed to recognize four orders of marine terraces located at elevations of 200 m, 120-90 m, 60-40 m, and 35-10 m a.s.l.. At Rocca Scodoni, between Acquedolci and Capo d’Orlando, the terrace located between 40 m and 60 m is characterized by the presence of a marine deposit up to 10 m thick, constituted by coarse polygenic conglomerates, microconglomerates and cross-laminated sands in a fining-upward sequence. Here, the inner margin of the terrace has been recognized between 45 m and 50 m a.s.l. and it is constituted by a cliff showing several Lithodomus holes, sometimes preserving fossilized shell inside, and other biological remains. A shell of Spondylus s.p. (Fig. 1) in physiologic position has been collected from this terraced deposit at Rocca Scodonì (Fig. 2) in order to perform geochronological analyses. The preliminary U/Th analysis on Spondylus shell, provides an age (with large error bar) on MIS 5 (between 100 and 125 ka). Based on the eustatic level for Mediterranean sea during Last Interglacial (6 metres ±3), the altitude of the inner margin (50 m) we estimate the tectonic uplift rate between 0.36-0.5 mm/a. Archaeological markers occurring along the coastal area located a few kilometers east of Rocca Scodonì (SCICCHITANO et alii, 2010) suggest similar tectonic uplift rates for the Holocene. The new chronological data allow us to calibrate, with respect to the Stage 5, the distribution of marine terraces recognized in this coastal area at different altitudes.

In the frame of the CARG Project, the interpretation of several seismic reflection profiles has provided new important constraints aimed at clarify the deep structural setting of the Central-Western Sicily and the related offshore fold and thrust belt. It has already been envisaged as a tectonic pile mainly made up of deep water Meso-Cenozoic carbonate units overriding a thick stack of Meso-Cenozoic carbonate platform units, detached from their crystalline basement. The data collected, constrained by wells logs, field and stratigraphic data, have improved the knowledge of a complex sector outcropping in the Corleone and Caccamo geologic sheets area. Seismic interpretation displayed the relationships between outcropping and deep-seated tectonic elements, focussing on the occurrence of a variable structural organization in the different sectors of the study area.