North Of Sicily Research Articles

Growth variability in Atlantic horse mackerel Trachurus trachurus (Linneus, 1758) across the central Mediterranean Sea: contrasting latitudinal gradient and different ecosystems

Data on Atlantic horse mackerel Trachurus trachurus (Linneus, 1758) were collected along 8-year acoustic surveys (2011-2018). Age and growth variability of horse mackerel from the Central Mediterranean Sea were investigated within different, contrasting habitats, from the south of Sicily to the north Tyrrhenian (Ligurian Sea). Data from satellite provided the habitat features along the study period over the whole surveyed area. For comparison purposes, according to the ecosystems difference the study area has been split into four subareas: Strait of Sicily (SoS), North of Sicily (NS), south Tyrrhenian Sea (ST) and north Tyrrhenian Sea (NT). In terms of the FAO Geographical Sub-Area definition the SoS corresponding to GSA15 and 16, NS to GSA 10 south, ST to GSA10 north and NT to GSA 9. Results showed a growth homogeneity in the study area, suggesting a unique stock inhabiting these waters. The only exception was recorded for juveniles (Age 0 class) in the SoS, where a lower size at age was detected compared to other areas. A multiple linear modelling analyses suggested that variability in length at age 0 was mainly linked to the oceanographic differences between an upwelling driven system (Strait of Sicily) and the other ecosystems, where enrichment processes are mainly due to river runoff (relevant in ST and NT). Namely, Absolute Dynamic Topography (ADT) and body condition factor (Kn) were significantly related to differences in length at age 0. Results revealed that currents (and gyres) are among the principal abiotic factors controlling Atlantic horse mackerel growth in its first year of life, suggesting that circulation and food-related processes (i.e., zooplankton concentration) are of major importance for this species. Finally preliminary observations suggest the Strait of Sicily may be the main spawning area among those analyzed.

Mucisphaera calidilacus gen. nov., sp. nov., a novel planctomycete of the class Phycisphaerae isolated in the shallow sea hydrothermal system of the Lipari Islands

For extending the current collection of axenic cultures of planctomycetes, we describe in this study the isolation and characterisation of strain Pan265T obtained from a red biofilm in the hydrothermal vent system close to the Lipari Islands in the Tyrrhenian Sea, north of Sicily, Italy. The strain forms light pink colonies on solid medium and grows as a viscous colloid in liquid culture, likely as the result of formation of a dense extracellular matrix observed during electron microscopy. Cells of the novel isolate are spherical, motile and divide by binary fission. Strain Pan265T is mesophilic (temperature optimum 30–33 °C), neutrophilic (pH optimum 7.0–8.0), aerobic and heterotrophic. The strain has a genome size of 3.49 Mb and a DNA G + C content of 63.9%. Phylogenetically, the strain belongs to the family Phycisphaeraceae, order Phycisphaerales, class Phycisphaerae. Our polyphasic analysis supports the delineation of strain Pan265T from the known genera in this family. Therefore, we conclude to assign strain Pan265T to a novel species within a novel genus, for which we propose the name Mucisphaera calidilacus gen. nov., sp. nov. The novel species is the type species of the novel genus and is represented by strain Pan265T (= DSM 100697T = CECT 30425T) as type strain.

Optimal design of stand-alone solutions based on RES + hydrogen storage feeding off-grid communities

Concerning off-grid areas, diesel engines still dominate the scene of local electricity generation, despite the related pollution concerns and high operating costs. There is thus a huge global potential, in remote areas, for exploiting local renewable energy sources (RES) in place of fossil generation. Energy storage systems become hence essential for off-grid communities to cope with the issue of RES intermittency, allowing them to rely on locally harvested RES.In this work, we analysed different typologies of off-grid renewable power systems, involving batteries and hydrogen as means to store energy, to find out which is the most cost-effective configuration in remote areas. Both Li-ion and lead-acid batteries were included in the analysis, and both alkaline and PEM electrolysis technologies were considered for the production of hydrogen. Starting from single cell electrochemical models, the performance curves of the electrolyser and fuel cell devices were derived for a more detailed techno-economic assessment. Lifetimes of batteries and H2-based components were also computed based on how the power-to-power (P2P) system operates along the reference year. The particle swarm optimization (PSO) algorithm was employed to find the component sizes that allow minimizing the levelized cost of energy (LCOE) while keeping the off-grid area energy autonomous. As a case study, the Ginostra village, on the island of Stromboli (North of Sicily, Southern Italy), was analysed since it is well representative of small insular locations in the Mediterranean area. The renewable P2P solution (0.51 €/kWh for the cheapest configuration) was found to be economically preferable than the current existing power system relying on diesel generators (0.86 €/kWh). Hydrogen, in particular, can prevent the oversizing of both battery and PV systems, thus reducing the final cost of electricity delivered by the P2P system. Moreover, unlike diesel generators, the RES-based configuration allows avoiding the production of local air pollutants and GHG emissions during its operation.

Quaternary Seismostratigraphy and Tectonosedimentary Evolution of the North Tunisian Continental Margin

AbstractNorthern Tunisia contains the poorly defined boundary between the Nubia and Eurasian plates. Offshore north Tunisia, the continental margin is interpreted to be part of the North Africa collisional fold and thrust belt system, linking the Maghrebian and the Sicilian‐Apennine chains. The Tunisia margin deforms by a slow NW‐SE trending convergence resulting in a diffuse deformation zone with scarce and scattered seismicity, in contrast to the neighboring regions of north Algeria and north Sicily. The complex recent evolution of this region is poorly known due to the paucity of studies, particularly offshore in the north Tunisian continental margin. Here, we present the seismostratigraphic analysis of the last ~1.8 Ma tectonosedimentary evolution of this area. The seismostratigraphic analysis supports that individual Quaternary depocenters developed syntectonic to faulting and that faulting influenced sedimentation patterns. We identify an abrupt variation in the sediment accumulation rates (SARs) coeval to a change in the strata geometry of the units located near faults at 402 ± 5 ka (mid‐Middle Pleistocene), supporting a change in the rate of faulting associated to contraction tectonics. This change indicates that deformation is controlled by the NW‐SE convergence between Nubia and Eurasia, probably accelerated at the end of extension in the Tyrrhenian back‐arc. Therefore, the current driving mechanism in the Central Mediterranean is possibly lithospheric collision between Nubia and Eurasia.

Rubinisphaera italica sp. nov. isolated from a hydrothermal area in the Tyrrhenian Sea close to the volcanic island Panarea

Planctomycetes is a fascinating phylum of mostly aquatic bacteria, not only due to the environmental importance in global carbon and nitrogen cycles, but also because of a unique cell biology. Their lifestyle and metabolic capabilities are not well explored, which motivated us to study the role of Planctomycetes in biofilms on marine biotic surfaces. Here, we describe the novel strain Pan54T which was isolated from algae in a hydrothermal area close to the volcanic island Panarea in the Tyrrhenian Sea, north of Sicily in Italy. The strain grew best at pH 9.0 and 26 °C and showed typical characteristics of planctomycetal bacteria, e.g. division by polar budding, formation of aggregates and presence of stalks and crateriform structures. Phylogenetically, the strain belongs to the genus Rubinisphaera. Our analysis suggests that Pan54T represents a novel species of this genus, for which we propose the name Rubinisphaera italica sp. nov. We suggest Pan54T (= DSM 29369 = LMG 29789) as the type strain of the novel species.

Co-inertia multivariate approach for the evaluation of anthropogenic impact on two commercial fish along Tyrrhenian coasts

Aliphatic hydrocarbon levels were determined by the GC/MS technique in fish livers of Engraulis encrasicolus (Ee) and Trachurus trachurus (Tt), collected from a particular area of the Mediterranean Sea, called GSA 10, which is located exactly in Tyrrhenian Sea between Campania coast and North Sicily coast. The aim was to evaluate their potential use as specific bioindicators towards this class of contaminants. Both Tt and Ee are considered to be pollution monitoring bioindicators, due to their dominance in marine communities and economic fishing interest. Ee showed a higher tendency to bioaccumulate TAHs, due to the lower quantity of fatty acids in liver tissues with respect to Tt. The area under study has been characterised a) chemically with the acquisition of temperature, oxygen and salinity profiles along the water column, and b) ecologically with the determination of amino acid contents in fish eyes, in order to gain information on the adaptation to environmental changes. Moreover, specific activities of two hydrolytic enzymes, such as alkaline phosphatase and peroxidase in fish epidermal mucus, together with lactate in blood plasma and cortisol levels, have been investigated for the first time, in order to obtain insights into the effects of hydrocarbons on animal welfare. A multiple co-inertia analysis was also applied to chemical and environmental parameters, in order to explore any possible correlation between different variables. The multivariate approach showed a clear spatial distribution between environmental and chemical variables in Ee, whilst there was an absence of a spatial trend in Tt. Moreover, the chemometric analysis showed a very high correlation between amino acid profiles and environmental variables for both species, confirming the possibility of being used as ecological welfare indices for short-term environmental variations.

Evolutionary and demographic correlates of Pleistocene coastline changes in the Sicilian wall lizardPodarcis wagleriana

AbstractAimEmergence of coastal lowlands during Pleistocene ice ages might have provided conditions for glacial expansions (demographic and spatial), rather than contraction, of coastal populations of temperate species. Here, we tested these predictions in the insular endemic Sicilian wall lizardPodarcis wagleriana.LocationSicily and neighbouring islands.MethodsWe sampled 179 individuals from 45 localities across the whole range ofP. wagleriana. We investigated demographic and spatial variations through time using Bayesian coalescent models (Bayesian phylogeographic reconstruction, Extended Bayesian Skyline plots, Isolation‐with‐migration models) based on multilocusDNAsequence data. We used species distribution modelling to reconstruct present and past habitat suitability.ResultsWe found two main lineages distributed in the east and west portions of the current species range and a third lineage restricted to a small area in the north of Sicily. Multiple lines of evidence from palaeogeographic (shorelines), palaeoclimatic (species distribution models), and multilocus genetic data (demographic and spatial Bayesian reconstructions) indicate that these lineages originated in distinct refugia, located in the north‐western and south‐eastern coastal lowlands, during Middle Pleistocene interglacial phases, and came into secondary contact following demographic and spatial expansions during the last glacial phase.Main conclusionsThis scenario of interglacial contraction and glacial expansion is in sharp contrast with patterns commonly observed in temperate species on the continent but parallels recent findings on other Mediterranean island endemics. Such a reverse expansion–contraction (EC) dynamic has been likely associated with glacial increases of climatically suitable coastal lowlands, suggesting this might be a general pattern in Mediterranean island species and also in other coastal regions strongly affected by glacial marine regressions during glacial episodes. This study provides explicit predictions and some methodological recommendations for testing the reverseECmodel in other region and taxa.

Comparing methods for computation of run-up heights of landslide-generated tsunami in the Northern Sicily continental margin

The North Sicily continental margin is a very active region located in the Central Mediterranean. Strong seismicity, active tectonics and volcanism, fluid escape, high sediment supply, and widespread mass movements historically have exposed this region to marine geohazards, with a potential for tsunami generation. Morpho-bathymetric analysis revealed that one of the most common mechanisms associated with marine geohazards is due to submarine mass failure processes, genetically linked to the other processes active in this margin. With the aim to assess the risks associated with landslide-generated anomalous waves, we selected two sectors of this margin, Gulf of Palermo to the west and Patti offshore to the east. The workflow included analysis of the morpho-bathymetric data, morphometric characterization, calculation of parameters of landslide-generated waves, and computation of run-ups by using different algorithms. Assuming that each of the identified landslides could be a potential tsunamigenic source, we calculated the associated theoretical run-ups, referring to the main computation methodologies proposed in the scientific literature. In order to identify the methodology that better suits run-up values for landslide-generated tsunami, we compared the known run-up values of actual, historical cases with those calculated through the different methodologies. The values obtained with the most suitable equation, both for theoretical and historical events, fit a curve that we used to formulate an empirical law describing the relationships between amplitude and depth, at the source point, and relative run-up. It can be used to calculate easily and promptly the run-up associated with a generic landslide-generated tsunami.

Ptilophora variabilis Hartig, 1968, bona species, and description of Ptilophora nebrodensis sp. n. from Sicily (Lepidoptera, Notodontidae).

In this paper, we redescribe Ptilophora plumigera variabilis Hartig, 1968 and raise it to species rank. Furthermore we describe Ptilophora nebrodensis sp. n. from Sicily, as the third European species belonging to the genus Ptilophora Stephens, 1828. These two species are allopatric vicariants of Ptilophora plumigera (Denis Schiffermüller, 1775) respectively in Apennine Italy and Sicily. We present the differential features mainly concerning the morphology of genitalia and molecular data. Ptilophora variabilis shows a scattered distribution, generally very localized, whereas P. nebrodensis sp. n. is restricted to a few localities in the mountainous areas of North Sicily, being very rare. Both species predominantly inhabit forests in mountain areas, with occurrence of broadleaved trees, especially Acer spp. (Fam. Aceraceae).

The contribution of Sicilian historical gardens to biodiversity conservation

The potential value of private gardens for enhancing biodiversity has long been recognized, while, less investigated is the contribution of historical gardens. The complex history of Sicily, with its strategically central position in the Mediterranean basin, made the island an important crossroad of civilizations and also influenced the use of ornamental plants in gardens over the centuries. With the aim to investigate the biodiversity of historical gardens of Milazzo (North of Sicily), the flora of 31 gardens, dating from the late 19th to the early 20th century, were analyzed through a complete plant inventory. The gardens are localized in two areas: the first ('Piana' = 13 gardens) close to the rural area, the second ('Capo' = 18 gardens) close to the residential area. The determinants of taxonomic richness in individual gardens were carried out with the use of Shannon (H'), Simpson (D) and Evenness (J) indices. The values of the indices are, respectively for 'Capo' and 'Piana', 5.7 and 5.5 for H', 0.8 for J and 0.0046 and 0.0054 for D, and demonstrate the presence of a high biodiversity and an even distribution of individuals per species, with a few dominant species. In the 31 gardens, 529 taxa of ornamental plants were identified, belonging to 343 genera and 117 botanical families. The richness of species found in these green areas allow to consider them as living plant collections. About 80% of the taxa were present in less than 10% of the gardens; 43.5% of species were present in a single garden. Only one species (Cycas revoluta Thunb.) was present in 87.1% of gardens to underline the species diversity.

Seismotomographic detection of major structural discontinuity in northern Sicily

We present the results of tomographic inversion computed with the use of the LOTOS code for Sicily and surroundings, a region of great geodynamic interest located on the Nubia-Europe margin where previous analyses have progressively improved the knowledge of seismic velocity structure without, however, permitting fine detection of tectonic units and structural discontinuities. We used LOTOS's devices for inversion, grid rotation and adaptation to ray density for application to a dataset of 7105 local earthquakes of the period 1990-2012. Our tomographic model highlights a previously undocumented major discontinuity which is located approximately along the northern coast of Sicily and is characterized by a sudden transition from low velocity imbricate thrust sheets and accretionary wedge in mainland Sicily (to the south) to relatively high velocity Tyrrhenian continental crust (to the north). Combining this finding with available geological and geodynamic information, we conclude that this northern Sicily seismic velocity discontinuity, which approximately corresponds to a regional fault system known as Kumeta-Alcantara, may have played a major role in the Miocene to Middle Pliocene, when lithosphere tearing occurred between the Tyrrhenian sea and Sicily in response to trench retreat. The more recent geodynamic settings of northern Sicily and the southern Tyrrhenian can be unravelled from Quaternary geological observations, seismicity and GPS data, which indicate that (i) the northern Sicily discontinuity has ceased to be active in more recent times; and (ii) the reorganized slow convergence of Nubia with respect to Europe is currently accommodated ~100 km north of Sicily, along the east-trending seismogenic belt enclosing Ustica and the Aeolian Islands.

Geomorphological evolution of western Sicily, Italy

Abstract This paper proposes a morphoevolutionary model for western Sicily. Sicily is a chain–foredeep–foreland system still being built, with tectonic activity involving uplift which tends to create new relief. To reconstruct the morphoevolutionary model, geological, and geomorphological studies were done on the basis of field survey and aerial photographic interpretation. The collected data show large areas characterized by specific geological, geomorphological, and topographical settings with rocks, landforms, and landscapes progressively older from south to north Sicily. The achieved results display: (1) gradual emersion of new areas due to uplift, its interaction with the Quaternary glacio-eustatic oscillations of the sea level, and the following production of a flight of stair-steps of uplifted marine terraces in southern Sicily, which migrates progressively upward and inwards; in response to the uplift (2) triggering of down-cutting processes that gradually dismantle the oldest terraces; (3) competition between uplift and down-cutting processes, which is responsible for the genesis of river valleys and isolated rounded hills in central Sicily; (4) continuous deepening over time that results in the exhumation of older and more resistant rocks in northern Sicily, where the higher heights of Sicily are realized and the older forms are retained; (5) extensional tectonic event in the northern end of Sicily, that produces the collapse of large blocks drowned in the Tyrrhenian Sea and sealed by coastal-marine deposits during the Calabrian stage; (6) trigger of uplift again in the previously subsiding blocks and its interaction with coastal processes and sea level fluctuations, which produce successions of marine terraces during the Middle–Upper Pleistocene stages.

Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)

The Egadi Marine Protected Area (MPA) on the western side of the Sicily Channel (Central Mediterranean) is exposed to a high risk of oil pollution from the tanker routes connecting the eastern and western basins of the Mediterranean Sea. Areas where an oil spill would do most damage, and thus where surveillance should be concentrated, are identified in this study by Lagrangian tracers tracked backwards in time from points along the MPA perimeter using data spanning six years from 2006 to 2011. Results indicate that the areas where oil surveillance would be most beneficial are segments of the tanker routes south of Sicily (highly frequented) and north of Sicily (scarcely frequented), both extending about 150 miles from November to March and 100 miles in the other months. The third route, close to the Tunisian shore, is the most frequented by oil tankers but the threat period is limited to November and December.

Grassland fire effect on soil organic carbon reservoirs in a semiarid environment

Abstract. The aim of this work was to investigate the effect of an experimental fire used for grassland management on soil organic carbon (SOC) stocks. The study was carried out on Hyparrhenia hirta (L.) Stapf (Hh) grassland and Ampelodesmos mauritanicus (Desf.) T. Durand & Schinz (Am) grasslands located in the north of Sicily. Soil samples were collected at 0–5 cm before and after the experimental fire, and SOC was measured. During the grassland fire, soil surface temperature was monitored. Biomass of both grasses was analysed in order to determine dry weight and its chemical composition. The results showed that SOC varied significantly with vegetation type, while it is not affected in the short term by grassland fire. Am grassland stored more SOC compared with Hh grassland thanks to lower content in the biomass of the labile carbon pool. No significant difference was observed in SOC before and after fire, which could be caused by several factors: first, in both grassland types the measured soil temperature during fire was low due to thin litter layers; second, in a semiarid environment, a higher mineralization rate results in a lower soil carbon labile pool; and third, the SOC stored in the finest soil fractions, physically protected, is not affected by fire.

Bulk rock composition and geochemistry of olivine-hosted melt inclusions in the Grey Porri Tuff and selected lavas of the Monte dei Porri volcano, Salina, Aeolian Islands, southern Italy

Abstract The Aeolian Islands are an arcuate chain of submarine seamounts and volcanic islands, lying just north of Sicily in southern Italy. The second largest of the islands, Salina, exhibits a wide range of compositional variation in its erupted products, from basaltic lavas to rhyolitic pumice. The Monte dei Porri eruptions occurred between 60 ka and 30 ka, following a period of approximately 60,000 years of repose. The bulk rock composition of the Monte dei Porri products range from basaltic-andesite scoria to andesitic pumice in the Grey Porri Tuff (GPT), with the Monte dei Porri lavas having basaltic-andesite compositions. The typical mineral assemblage of the GPT is calcic plagioclase, clinopyroxene (augite), olivine (Fo72−84) and orthopyroxene (enstatite) ± amphibole and Ti-Fe oxides. The lava units show a similar mineral assemblage, but contain lower Fo olivines (Fo57−78). The lava units also contain numerous glomerocrysts, including an unusual variety that contains quartz, K-feldspar and mica. Melt inclusions (MI) are ubiquitous in all mineral phases from all units of the Monte dei Porri eruptions; however, only data from olivine-hosted MI in the GPT are reported here. Compositions of MI in the GPT are typically basaltic (average SiO2 of 49.8 wt %) in the pumices and basaltic-andesite (average SiO2 of 55.6 wt %) in the scoriae and show a bimodal distribution in most compositional discrimination plots. The compositions of most of the MI in the scoriae overlap with bulk rock compositions of the lavas. Petrological and geochemical evidence suggest that mixing of one or more magmas and/or crustal assimilation played a role in the evolution of the Monte dei Porri magmatic system, especially the GPT. Analyses of the more evolved mineral phases are required to better constrain the evolution of the magma.

Description of Chone usticensis sp. nov. (Polychaeta, Sabellidae) from the Mediterranean Sea

A new species of Chone (Sabellidae) from the coast of Ustica Island (Mediterranean Sea, north of Sicily) is described. The species, named Chone usticensis sp. nov., is similar to another Mediterranean species, C. filicaudata, in having a long pygidial filiform appendage, but is distinct from this species especially in the peristomium, collar, and in thoracic paleate chaetae shape. A discussion on the presence of the radiolar appendages within the genus Chone is also given.

Seismic Broadband Ocean-Bottom Data and Noise Observed with Free-Fall Stations: Experiences from Long-Term Deployments in the North Atlantic and the Tyrrhenian Sea

In a comparative study of two long-term deployments we characterize the seismic noise on the seafloor in the North Atlantic south of Iceland and in the Tyrrhenian Sea north of Sicily. We estimate the teleseismic body-wave detection threshold to be approximately magnitude 6.0 at frequencies below the microseismic band (f 0.1 Hz) on vertical components at the quietest sites in both regions. At the microseismic peak (0.25 Hz) in the North Atlantic, the minimum magnitudes for events to be recorded most of the time are Mw 7.0 for the Tyrrhenian Sea deployment and above 8 for the North Atlantic deployment. By correlating seismic noise and oceanic waveheight amplitudes we are able to find the major generation areas of microseismic noise in the North Atlantic. Although the high noise of secondary microseisms at 0.24 Hz is generated far away from the ocean-bottom stations at three near-coastal regions, the microseismic noise at about 1 Hz is generated directly at the stations. We present a technique to estimate the noise generation areas prior to future deployment by using noise at nearby land stations. The ambient low-frequency noise below 0.1 Hz occurs mainly on horizontal components and is probably induced by seafloor-current-induced tilt. The power spectral density of this noise varies by a factor of up to 10,000 between different stations and deployment sites, indicating in some cases wobbling deployments, possible problems of frame weakness, and a possible higher noise sensitivity of external packs to seafloor currents. Cross-coupling between horizontal and vertical channel noise is strong at some of our stations, demonstrating that the leveling mechanics can be further improved to reduce vertical channel noise.

Structural highs formation and their relationship to sedimentary basins in the north Sicily continental margin (southern Tyrrhenian Sea): Implication for the Drepano Thrust Front

Two high-penetration seismic profiles across the continental margin of north Sicily (southern Tyrrhenian Sea) have been interpreted to construct a crustal section across the margin and to provide a three-dimensional perspective on the upper crustal setting of the Solunto High and its structural relationships with the adjacent Cefalù Basin. Crystalline rocks of the Kabilian–Calabrian Units (KCU) are recognized in the Solunto High region and farther to the north. The KCU body is tectonically superimposed onto sedimentary rocks pertaining to the Sicilian–Maghrebian Units (SMU) and the Solunto High corresponds to the thrust sheet culmination. Its occurrence in the Solunto High demonstrates that the Drepano Thrust Front is continuous from the Elimi Chain in the west to the Calabrian–Peloritani in the east. At the crustal scale, the continental margin of north Sicily shows tectonics features typical of most subduction zones and of rifted continental margins. Continental collision was achieved in the (?) Oligocene–early Miocene and caused the superposition of the KCU crystalline rocks on the deep-water carbonate resting on the African continental margin. Contractional deformation persisted until the late Miocene resulting in the tectonic superposition of deep- onto shallow-water carbonates and the formation of the Sicilian–Maghrebian fold-and-thrust belt. Extension began in late (?) Tortonian times, lasted till the early (?) Messinian and caused the opening of the Cefalù Basin and other basins further to the north. Late (?) Messinian–early Pliocene contractional and/or transpressional deformation reactivated previously formed oblique ramps in the inner sector of the thrust belt. This event was responsible for uplift of the KCU in the Solunto High region. In the middle–late Pliocene, renewed extension determined further opening and subsidence of the Cefalù basin. Lithospheric breakup took place in the late Pliocene. Presently, the north Sicily offshore is a zone of compressive stress and the area north of Solunto High is a zone of weakness.

An improved stress map for Italy and surrounding regions (central Mediterranean)

We present an updated present‐day stress data compilation for the Italian region and discuss it with respect to the geodynamic setting and the seismicity of the area. We collected and analyzed 190 new stress data from borehole breakouts, seismicity, and active faults and checked in detail the previous compilation [Montone et al., 1999]. Our improved data set consists of 542 data, 362 of which with a reliable quality for stress maps. The Italian region is well sampled, allowing the computation of constrained smoothed stress maps; for surrounding regions we added the World Stress Map 2003 release data. These maps depict the active stress conditions and, in the areas where the data are sparse, contribute to understand the relationship between active stress, past tectonic setting, and the seismicity of the study region. The new data are particularly representative along the northern Apennine front, from the Po Plain to offshore the Adriatic, and along the southern Tyrrhenian Sea, north of Sicily, where they point out a compressive tectonic regime. In the Alps both compressive and transcurrent regimes are observed. Our data also confirm that the whole Apenninic belt and the Calabrian arc are extending. Along the central Adriatic coast, changes from one stress regime to another are shown by abrupt variations in the minimum horizontal stress directions. Other gentler stress rotations, as, for instance, from the southern Apennines to the Calabrian arc or along the northern Apennines, follow the curvature of the arcs and are not associated to a stress regime variation.

Tectono-stratigraphic modelling of the North Sicily continental margin (southern Tyrrhenian Sea)

A two-dimensional numerical modelling that simulate the kinematic and thermal response of the lithosphere to thinning was used for the quantitative reconstruction of the late Neogene to Recent times tectonic and stratigraphic evolution of the North Sicily continental margin (southern Tyrrhenian Sea). The numerical study of the evolution of the North Sicily margin builds on the crustal image and kinematic interpretation of the margin obtained by Pepe et al. [Tectonics 19 (2000) 241] on the basis of seismic data and gravity modelling. Tectonic modeling indicate that different segments of the margin were undergoing different vertical movements, which are mainly expression of the rifting and thinning of the lithosphere occurred during tectonic evolution of the southern Tyrrhenian Sea. A prediction of the pre-rift basement topography and the Moho along the margin converges to a value of 6.5 km for the depth of necking and a temperature-dependent EET (500° isotherm). The model fails to reproduce the morphology of the Solunto High confirming its non-extensional origin. A polyphase evolution is required to reproduce the observed syn- and post-rift stratigraphy. During the first rifting stage (between 9 and 5 Ma), crustal thinning factors reach maximum values of ∼1.27 in the Cefalù basin. A similar value is predicted for the subcrustal thinning around 60 km NNE of the profile margin. Crustal thinning factors increase during the second rifting stage (from 4 to 2 Ma) and reach values of ∼2 and up to 3.5 in the Cefalù basin and in the continent–oceanic transition zone, respectively. Similarly, subcrustal lithospheric thinning factors reach values up to 2.5 in the distal sector of the margin. An uplift of more than 100 m is predicted for the North Sicily shelf and surrounding onshore areas during the post-rift stage. The evolution of thermal structure with time is very sensitive to the partial thinning factors describing the evolution of the thinning itself during time. The lithosphere preserved part of its strength during extension. The effective elastic thickness (EET) along the margin through time is ∼24 km at the onset of rifting and reaches values less to ∼8 km during the second rifting stage in the northeastern end of the margin.