Southeastern Sicily Research Articles

Helium isotopes in peridotite mineral phases from Hyblean Plateau xenoliths (south-eastern Sicily, Italy)

Fourteen He isotope and abundance analyses have been performed on olivine, orthopyroxene, and clinopyroxene grains from selected spinel-facies peridotite xenoliths collected from the Hyblean Plateau, southeastern Sicily. These peridotites consist of protogranular-textured, spinel-facies lherzolites and lherzolitic harzburgites. Microthermometric data on olivine and pyroxenes reveal that the fluid inclusions (FIs) are nearly pure CO 2, with densities ranging from 0.76 to 1.15 g/cm 3. The densest inclusion trail occurs in an orthopyroxene grain and indicates a trapping-pressure of 0.98–1.14 GPa (estimated equilibration temperature of 1000 °C for pure CO 2 system) corresponding to a depth of ∼ 36–41 km (for an average estimated density of the lithospheric column of 2.85 g/cm 3). These are minimum estimates. The near-unimodal distribution of CO 2 densities indicates that these xenoliths have been stored at the pressure interval of 0.75–0.95 GPa—corresponding to a depth of ∼ 27–35 km (crust–mantle boundary or just below). En route to the surface, they have not had any significant interaction with shallower volatile reservoirs. He trapped in CO 2-rich fluid inclusions ranges in abundance from 1.8 to 86.6×10 − 9 cm 3 STP/g, with clinopyroxenes usually showing higher He contents than coexisting olivines and orthopyroxenes. The inter-mineral differences are due to physical properties of minerals. In contrast, He isotope ratios cover a narrow range (∼ 7.3 ± 0.3 R A, where R A = air 3He/ 4He), indicating isotopic equilibration between the mineral phases. He composition indicates a MORB-type source for the metasomatic agent(s), influenced by relatively minor radiogenic production in the source. Therefore, in closed-system conditions, the calculated helium residence time is 790 Myr. Geophysical and geochemical studies suggest the existence of a common fluid reservoir in the mantle beneath the Central Mediterranean area. The most pristine He signature for the mantle endmember is found on Pantelleria Island (Sicily Channel): this He ratio is similar to that found in Hyblean peridotite minerals, testifying to a common source history. We conclude, therefore, that Hyblean xenoliths can be used as a powerful tool in defining the geochemical features of this portion of the upper mantle.

Trace metals in “ Posidonia oceanica ” seagrass from south-eastern Sicily

Heavy-metal concentrations were measured in sediments and tissues of Posidonia oceanica seagrass from south-eastern Sicily (Italy) in order to assess the degree of metal pollution in the coastal area. Seagrasses and sediments were collected at four sites along the south-eastern coast of Sicily. Flame atomic absorption spectrophotometry (FAAS) was used to measure concentrations of Cu, Zn, Cd and Pb. Standard statistical analyses were used to assess significant differences among the levels of the elements measured in different tissues and sediment and spatial distribution. The greatest values of potentially toxic metal concentrations were observed at the station near the industrial sites of Augusta and Priolo. Comparisons with the concentrations of the same metals in other sites of north and western Sicily and with data from surveys in other areas of the Mediterranean Sea are shown.

Inconsistent patterns of historical seismicity and earthquake-triggered landsliding in southeastern Sicily: an alarm bell?

In southeastern Sicily, the distribution pattern of earthquake-triggered landslides is inconsistent with historically known seismic activity. In particular, historical seismicity has been stronger in the eastern sector, while earthquake-triggered landsliding is much more developed in the western sector, and this contrasts with expectations. This paper describes the patterns of seismicity and landsliding, and tackles the problem of whether greater landsliding in the western sector may be due (a) to seismicity of the eastern sector or (b) to a high-magnitude, low-recurrence seismicity generated in the western sector itself. It is statistically shown that lithostructural characteristics of rock masses and geometry of hillslopes cannot justify, either singly or jointly, greater landsliding in the western sector if triggering earthquakes are generated in the eastern sector. As a consequence, it is possible that landsliding of the western sector is due to earthquakes generated locally, but having higher magnitude and longer recurrence intervals than historically observed.

Late Pliocene volcanic island growth and flood basalt‐like lava emplacement in the Hyblean Mountains (SE Sicily)

Since ∼200 Ma, the Hyblean Mountains (southeastern Sicily) have been the site of recurrent, mainly submarine, mafic volcanism. In the upper Pliocene, large volumes of tholeiitic products were erupted in a shallow marine environment, leading to the growth of volcanic islands. The deposits of this tholeiitic episode can be grouped into two main facies associations: (1) pillow lavas and hyaloclastite tuffs erupted and deposited entirely under water, and (2) submarine pillow breccias, fed from subaerial lava flows entering the ocean and subaerial lavas, which are distinguished into a coastal lava platform facies and an inland facies. Lava flows into the ocean led to the growth of lava deltas consisting of a basal flow foot breccia and an overlying sequence of pāhoehoe flow units, the latter rarely exceeding 0.5 m in thickness. In outcrop, this facies association shows evidence for significant instability of the lava deltas during growth, indicating very similar processes to those observed during the current eruption of Kīlauea volcano, Hawaii. Away from the coast of the growing island, the inland facies is characterized by thicker (up to several meters) pāhoehoe flow units showing evidence for sheet flow inflation and limited outcrops of scoria and/or bomb deposits. Evidence for lava transport through tubes exists in the form of tumuli and multiple vesicle layers; drained tubes are absent. All tholeiitic products were emitted in a single, instantaneous, voluminous event (≥120 km3), consistent with very high effusion rates similar to those of flood basalts or the 1783 Skaftár Fires (Iceland) eruption.

Source and Qp parameters from pulse width inversion of microearthquake data in southeastern Sicily, Italy

Source and Qp parameters were estimated from the inversion of first arrival P waveform durations of about 300 microearthquakes recorded at a digital seismic network operating in southeastern Sicily. The average risetime and pulse width at each station do not show large differences, allowing us to exclude significant differential attenuation site effects. A first Qp estimate was obtained by applying the classical risetime method, under the assumption of a point‐like source time function. In order to investigate the effect of directivity due to the finiteness of seismic sources, new nonlinear relationships, based on a circular crack model rupturing at a constant velocity, were numerically built. These relationships were used to formulate a nonlinear inverse method for retrieving source (radius, dip, and strike of the circular crack) and Qp parameters from the inversion of risetime and pulse width data. The application of the method produced a better fit of the observed data and a Qp value higher than that obtained by applying the risetime method. The discrepancy between the different Q estimates may be due to a trade‐off among source dimension and Qp, as we inferred from a test on a subset of low‐magnitude events (Ml ≤ 2.5). A good agreement with independent estimates of fault plane solutions, as inferred from P polarities and S polarizations, was found. The estimated stress drops are generally very low (0.1–10 bars). This suggests that the background seismic activity in southeastern Sicily is related to fault segments and/or weakened zones where great stress accumulations are hindered.

Intrinsic and scattering attenuation from observed seismic codas in Southeastern Sicily (Italy)

We analyzed about 150 local earthquakes recorded in Southeastern Sicily from 1994 to 2001 and estimated coda- Q, intrinsic and scattering attenuation. We used the single scattering assumption to fit the amplitude envelopes of the coda at different frequency bands, obtaining a Q c varying with frequency as generally observed in tectonically active areas. Lapse time dependence has been also studied for the area, with the coda waves analyzed at window lengths ranging from 15 to 50 s, provided the coda duration permitted it. We found that Q 0 ( Q c at 1 Hz) increases with lapse time and we interpreted this as due to increasing Q c with depth. Conversely, the frequency dependence coefficient n is mostly stationary at all the lapse time window lengths. Finally, using the independent estimates of Q c and the total Q ( Q T) previously obtained for the area by other authors from direct S-waves of the same data set, we separated the intrinsic ( Q i −1) from the scattering ( Q sc −1) attenuation factor. The results suggest that in Southeastern Sicily intrinsic dissipation plays a predominant role with respect to scattering phenomena.

Status and conservation of herpetofauna from the Iblean area (south eastern Sicily)

The status of amphibians (5 species) and reptiles (16 species) from the Iblean area (south eastern Sicily) was been analysed taking into account the data from literature and, above all, those obtained during a research‐period of more than 10 years (1988–2001). All the 54 UTM squares (10x10 km) included in the Iblean area were investigated. The status of each species was defined following the criteria suggested by the IUCN on the basis of the diffusion in Sicily and in the Iblean area, the autoecology, and the risk factors deriving from human activities. The results confirmed a general sensitivity of amphibians, especially of Discoglossus pic‐tus and Hyla intermedia, the former widely distributed but endangered due to its insular distribution and to human impact, the latter very localised in the studied area and at the southernmost limit of its distribution. The reptiles were less sensitive, although some species need special protection due to the destruction of their habitats or commercial use (e.g., Emys orbicularis, Testudo hermanni and Zamenis situlus). Some general considerations on the main problems related to the conservation of the Iblean herpetofauna are provided: it is clear that the only way to guarantee an effective safeguarding of the biological communities is to create a ‘Regional Iblean Park’.

Minimum 1-D velocity model in Southeastern Sicily (Italy) from local earthquake data: an improvement in location accuracy

The monitoring of seismic activity inSoutheastern Sicily (Italy) has beenrecently improved by a digital seismicnetwork. This effort has produced ahomogeneous and complete dataset which weused to define a reference 1-D velocitymodel. We have inverted P- and S-wavearrival times from 51 selected localearthquakes by using several initialvelocity and layer thickness models. Then,the range of possible velocity modelsobtained was tested with earthquakelocations to select the best velocitymodel. Improvements in location accuracy byusing the Minimum 1-D velocity model, withrespect to the locations obtained by usingthe routine velocity model, were evidencedfrom the reduced residuals, the smallerestimated location errors, and theincreased tendency of foci to cluster. Thedistribution of relocated hypocentersconfirmed the lack of seismic activity inthe central part of the area.

Elevated incidence of hypospadias in two sicilian towns where exposure to industrial and agricultural pollutants is high

We found significant elevated incidence of hypospadias in two towns in Southeastern Sicily selected on the basis of the presence of intense industrial (Augusta) and agricultural (Vittoria) activities. Cases and controls were chosen in records collected from a surveillance system on abnormal live births in the same area and in a large city (Catania) located in an area at low risk of exposure to environmental pollutants. From 1991 to 1998, 16 cases of isolated hypospadias were recorded among male live births in Augusta (12.1 per 1000 male live births) and 24 cases in Vittoria (7.4 per 1000 male live births) with an incidence significantly higher than that expected (3.2 per 1000 in Southeastern Sicily). Relative risks in Augusta and Vittoria were 3.8 (95% confidence interval: 2.16–6.14) and 2.3 (95% confidence interval: 1.48–3.43; P=0.00003 and 0.04, respectively). In Augusta, the incidence of hypospadias was higher than in Vittoria. Significant log odds ratios were found for occupational exposure in fathers both in Augusta and Vittoria ( P=0.0478 and 0.026, respectively). However, daily contact with pollutants in Augusta may not be sufficient by itself to determine hypospadias and other factors might be involved. Similar factors may act also in Vittoria. Thus, contact with large amounts of pesticides is, by itself, a risk factor for hypospadias, though genetic and other environmental factors might be involved.

High-Precision Relative Locations of Two Microearthquake Clusters in Southeastern Sicily, Italy

In November 1999 and January 2000, two microearthquake swarms occurred in southeastern Sicily (Italy). They were analytically located in the depth range 17-25 km, some kilometers northward from the buried front of a regional foredeep, below the active thrust zone of the Sicily mountain chain. Their hypocentral distribution showed two distinct clusters, and comparison of the waveforms revealed clearly that the two swarms formed two distinct families of multiplet events. This led us to (1) carry out a precise relocation relative to two chosen master events of the families and (2) better define the geometrical structure of the two clusters. The cross-spectral method was applied to obtain precise readings of the wave onsets. SH wave onsets were used instead of P waves, as they showed clearer onsets and a good signal-to-noise ratio. Residuals of the relative locations showed small values, no more than several meters on average. The vertical extent of the two relocated clusters was 500 and 250 m, respectively, while the horizontal extent was 250 m. Hypocenters of the first cluster clearly delineate a north-northwest-trending plane with almost vertical dip, matching one nodal plane of the focal mechanism obtained as a composite solution of all events of the cluster. Given the considerable gap angles, because of unfavorable network geometry with respect to the events, the stability of our results was tested carrying out a Monte Carlo experiment. Varying the onset times randomly in the range of ±5 msec, a dispersion of the locations less than 10 m in longitude and less than 50 m both in latitude and depth was found. Similar results were obtained when comparing relocations carried out with different master events. Thus, the overall geometrical characteristics of the clusters were not affected seriously by random errors. Considering the geostructural framework of the region, together with the location and time evolution of the two clusters, fluids of plutonic origin are suggested as the trigger mechanism. Manuscript received 26 June 2002.

Scope for improvement in Czech paint

The city of Catania (Italy) in the South-Eastern Sicily has been affected in past times by several destroying earthquakes with high values of estimated magnitude. The seismogenic area to the south of Volcano Etna, known as Iblean Area, is placed between the African and the Euro-Asiatic plates on the west of the Ibleo-Maltese escarpment, to the south of the Graben of the Sicilian channel and on the east of the overlapping front of Gela. Basing on the seismic history of Catania, the following earthquake scenarios have been considered: the “Val di Noto” earthquake of January 11, 1693 (with intensity X-XI on MCS scale, magnitude MW=7.41 and epicentral distance of about 13 km); the “Etna” earthquake of February 20, 1818 (with intensity IX on MCS scale, magnitude MW=6.23 and epicentral distance of about 10 km). The soil response analysis at the surface, in terms of time history and response spectra, has been obtained by 1-D equivalent linear models for about 1200 borings location available in the data-bank of the central area of Catania of about 50 km2, using deterministic design scenario earthquakes as input at the conventional bedrock.Seismic microzoning maps of the city of Catania have been obtained in terms of different peak ground acceleration at the surface and in terms of amplification ratios for given values of frequency.

Thyroid hemiagenesis: prevalence in normal children and effect on thyroid function.

Thyroid hemiagenesis prevalence was studied by neck ultrasound examination in 24,032 unselected 11- to 14-yr-old schoolchildren from southeastern Sicily. Twelve cases of thyroid hemiagenesis were identified, with a prevalence of 0.05%. The female to male ratio was 1:1.4. Thyroid hemiagenesis was always due to the absence (11 cases) or severe hypoplasia (1 case) of the left lobe. The hemiagenetic thyroid volume was within the normal total thyroid volume range normalized to age in 4 of 12 cases, enlarged in 3, and significantly reduced in 5. Thyroid function (thyroid hormones and TSH, both basal and 30 min after administration of 200 micro g TRH, iv) was evaluated in 9 of 12 children and was always within the normal range. However, children with thyroid hemiagenesis had an average serum TSH significantly higher than that of 18 matched controls (2.8 +/- 0.6 vs. 1.9 +/- 0.5 mU/liter; P < 0.001). This study confirms that thyroid hemiagenesis is nearly always due to left lobe defect, and that its prevalence is similar to the cumulative prevalence of thyroid agenesis and ectopia. Compensatory hypertrophy of the residual thyroid lobe occurs in most, but not all, cases and is due to thyroid tissue overstimulation by TSH. The high risk of goiter and hypothyroidism suggests systematic follow-up of all identified cases of thyroid hemiagenesis.

Attenuation of body waves in Southeastern Sicily (Italy)

The attenuation of P- and S-waves in Southeastern Sicily was estimated by applying two different methods in time and frequency domains. We analyzed waveforms from about 290 local events (0.6≤ M L≤4.6) recorded at a three-component digital network. By applying the pulse broadening method to the first P-wave pulse, we found an average Q p value of ca. 140. The application of the frequency decay method provided a Q p value of ca. 120, in the low-frequency band (3–9 Hz). Conversely, in the high frequency range (16–27 Hz) the average Q p is significantly larger (ca. 640). The frequency decay method was also applied to S-waves spectra. In the low frequency range (2–5 Hz) the estimated average Q s is ca. 190. As for Q p, also Q s, in the high frequency range (16–27 Hz), is larger (ca. 700). These results evidenced a frequency dependence of both the quality factors Q p and Q s, as commonly observed in tectonically active zones characterized by high degree of heterogeneity.

Seven landslide dams of old seismic origin in southeastern Sicily (Italy)

This paper focuses on origin, morphology and evolution of seven landslide dams in southeastern Sicily. These landforms are part of a set of 146 landslides recently recognised in this area, which was hitherto considered to have little or no slope instability. Southeastern Sicily consists of a plateau (the Hyblaean Mountains) incised by canyons and surrounded by lower lands. It is underlain mostly by subhorizontal, moderately to well-lithified carbonate rocks. Relief is low. Several lines of evidence justify the assumption of a seismic trigger for the landslides in this area: (1) the geo-climatic environment is not favourable to landsliding, (2) low-angle basal shear surfaces are very frequent, (3) landslide distribution is consistent with the known magnitude–distance relationships for earthquake-induced landslides, (4) historical documents testify to earthquake-triggered slope instability and (5) a specific landslide can be exactly dated. The phenomena illustrated here include six rock slides (one with a debris-flow component) and one rock fall. Slip surfaces are mostly non-circular. Landslide volume ranges from about 50×10 3 to 34×10 6 m 3. With reference to the Costa and Schuster [Geol. Soc. Am. Bull. 100 (1988) 1054] classification of landslide dams, five cases belong to type II (spanning the entire valley), and two to type IV (failures from both valley sides, with frontal or side contact between failed masses). With reference to Crozier and Pillans [Catena 18 (1991) 471] classification of landslide lakes, all cases show a main valley lake while tributary valley, back and supra lakes are sporadically present. One damming is attributable to the 1693 earthquake with certainty; another damming, to the same earthquake with high probability. Three dams were reincised, one breached or reincised, one is slightly reincised and two more or less intact; correspondingly, five silting up deposits were reincised, one is being reincised at present and two are still under formation.

Plio-Pleistocene sedimentary facies and their evolution in centre-south-eastern Sicily: a working hypothesis

This paper examines the distribution and evo- lution of the Plio-Pleistocene sedimentary facies in centre- south-eastern Sicily, especially around Enna, Licata and Caltagirone. Sectors occur in this region (Caltanissetta- Enna-Centuripe, Pietraperzia-Barrafranca-Piazza Armerina- Butera, S. Michele di Ganzaria-Caltagirone-Niscemi, Licata- Gela) where, in relation to the late Zanclean-Piacenzian / Selinuntian period, the sedimentary succession has different lithostratigraphic characteristics. The area studied belongs to the Caltanissetta Basin, which is a paleogeographical-sedimentary unit. From the Late Mio- cene to the Quaternary period it consisted of a dynamic fore- deep basin between the Hyblean Foreland and the Apennine- Maghrebian Trust front. Between the Early Pliocene and Early Pleistocene periods this front advanced about 50 km southwards and south-eastwards. The Plio-Quaternary lithostratigraphic sequence is mainly represented by 11 units: Zanclean Trubi Fm, Pliocene Argille Brecciate Fm. (Pliocene Brecciated Clays-AB IV, V), Enna Marls of the late Zanclean-Piacenzian, Centuripe Sandstones and Capodarso Calcarenites of the late Zanclean-Piacenzian, Geracello Clayey Marls of the Piacenzian-Selinuntian, Pi- azza Armerina Sands of the Piacenzian-Selinuntian, Mt. S. Giorgio Marly Clays of the Selinuntian, Caltagirone-Niscemi Sands of the Selinuntian, Terraced sediments of the Middle- Late Pleistocene, Present day sediments. There are three clear unconformities in the sequence, ex- cluding the one at the base of the quaternary terraced de- posits. The first, of late Zanclean age, is located above the Trubi Fm., and developed immediately after the beginning of the Enna Marls sedimentation; it has a synsedimentary char- acter and developed in a marine environment without emer- gence. The second, of late Piacenzian age, lies at the base of the Geracello Clayey Marls, while the third (Selinuntian), is located at the base of the Mt. S. Giorgio Marly Clays. Mi- nor unconformities, probably of glacio-eustatic origin, are locally present.

Historical and geological evidence for seismic origin of newly recognized landslides in southeastern Sicily, and its significance in terms of hazard.

Old, large, and dormant landslides were unexpectedly found in southeastern Sicily, a territory of known seismicity but commonly considered as landslide-free or almost so. Purposely undertaken investigations revealed that: (1) these landslides are scarcely compatible with the local geoclimatic environment; (2) they usually show low-angle basal shear surfaces, despite the fact that the properties of the forming material are generally good; (3) they fulfill the known relationships between earthquake magnitude and epicenter-landslide distance; (4) sources coeval with high-energy historical earthquakes occurred in 1169, 1542 and 1693 testify to the occurrence of earthquake-triggered landsliding; and (5) documentary material (presented here for the first time) correlates with certainty a specific landslide to the 1693 earthquake. This geological and historical evidence, accompanied by the absence of contrasting elements, leads us to conclude that these landslides are earthquake-triggered. Because of their typological and geometrical characteristics, nearly all landslides can be reactivated, which has serious implications in terms of hazard, particularly with respect to lines of communication. Obviously, every action aimed at preventing or mitigating risks must start from the awareness of the causative processes, a condition substantially unsatisfied at the moment in SE Sicily. The paper concludes by emphasizing the opportunity not to trust excessively beliefs that, although shared, have never been really checked.

Attenuation in Southeastern Sicily (Italy) by applying different coda methods

The attenuation in Southeastern Sicily has been investigated using 40aftershocks of the December 13 1990, earthquake. The quality factor ofcoda waves (Qc) was estimated in the frequency range 1.5–24 Hz,applying three different methods in time and frequency domains. On thewhole, a clear dependence of Qc on frequency was observed,according to the general law Q = Q0(f/f0)n . Thefrequency dependence relationships obtained from the analysis of codawaves at three lapse time windows (10, 20 and 30 seconds) show that, forall methods, Q0 (Qc at 1 Hz) significantly increases with lapsetime. In particular, Q0 is approximately 20 at short lapse time (10s) and increases to about 70 at longer lapse time (30 s). This is attributedto the fact that larger lapse times involve deeper parts of the crust andupper lithosphere which may be characterized by larger quality factors.Moreover, the value of the exponent n decreases with increasing codalengths from about 1.3 to 0.9, suggesting a decrease in heterogeneity ofthe medium with depth.Finally, Qc-values here found are of the same order as thosereported from other tectonic regions like the Anatolian Highlands orSouthern Spain, while significantly higher than in the neighboring volcanicarea of Mt. Etna.

Contribution of tsunami data analysis to constrain the seismic source: the case of the 1693 eastern Sicily earthquake

The January 11, 1693 eastern Sicilyearthquake is comparable only with the December 28,1908 Messina Straits event in the Italian seismichistory as regards magnitude (ML ≅ 7), level ofdestruction and number of victims. The shock generateda strong tsunami, which hit the entire eastern coastof Sicily and particularly the town of Augusta. Theproblem of which fault was responsible for theearthquake is still open. Several hypotheses have beenformulated in the literature on the basis of differentkinds of geological, macroseismic and tectonic data,but a general agreement has not been reached yet. Animportant contribution to the discussion may come fromthe analysis of the tsunami data. In two previouspapers (Piatanesi et al., 1996; Piatanesi and Tinti,1998), the hydro-dynamical study of the tsunami basedon finite-element (FE) numerical simulations wascarried out taking into consideration mostlytheoretical faults, i.e. faults selected for theirsignificance in tsunami generation irrespective of thecorresponding geological evidence. This paper has tobe considered the continuation of the mentioned works.We have studied new sources proposed in theliterature, consistent with macroseismic data and/orgeological observations, and simulated thecorresponding tsunamis. We also built a new FE gridintroducing significant improvements in the coastlinerepresentation, and developed and applied a newalgorithm in order to account for the effect of thesea-bottom topography on the tsunami initialcondition. Some of the examined faults are located inthe Scordia-Lentini (SL) graben region and interceptthe coastline, others are placed in correspondencewith the Hyblaean-Malta (HM) escarpment and runparallel or sub-parallel to the coast. The conclusionof our work is that none of these faults respectsfully the available observations on tsunami, and thatthe faults exhibiting the best fit are those placed inthe SL region. It is worth stressing that our resultsare important for the assessment of seismic andtsunami hazard/risk in eastern Sicily, keeping also inmind that the 1693 earthquake has been selected as thereference event for an earthquake-scenario study inCatania and in south-eastern Sicily, called `CataniaProject', funded by CNR/GNDT (Consiglio Nazionaledelle Ricerche/Gruppo Nazionale Difesa dai Terremoti).

The social life of local museums

Through an ethnographic analysis of the social life of three non-anthropological 'museums' in a town in south-eastern Sicily, the contours of public space and public culture are examined in a political environment marked by deeply rooted political conflicts. Local and provincial 'politics of culture', a largely overlooked dimension in traditional anthropological approaches to politics in Sicily and Italy, are analysed. The article also investigates, from a Sicilian and ethnographic point of view, a proposition that underlies many recent North American studies on museums and the politics of culture. Employing a postmodern perspective, these studies have shown the political and conflictual character of museums. They are represented as institutions in which it is possible, if not indeed necessary,for the political and social tensions that roil public space to be represented in a controlled, dialogical form. Even when placed under the gaze of postmodern analysis, therefore, the museum is still viewed as retaining its character as a 'democratic' and public forum. This article looks at what happens in the case of 'museums' where public space assumes unexpected forms, less 'solid' and, instead, radically conflictual. In questo scritto, attraverso l'analisi etnografica della vita sociale di tre musei non antropologici di una piccola città della Sicilia sudorientale, l'autore esamina la conformazione della cultura e della spazio pubblici in un contesto connotato da forte e stratificata conflittualità politica. Intende così analizzare le 'politiche della cultura' messe in atto a livello locale e provinciale, una dimensione spesso poco considerata dagli studi antropologici tradizionali sulla Sicilia e l'Italia. Cerca, in conclusione, di mettere in evidenza e criticare, da un punto di vista etnografico e siciliano, un assunto di molte recenti analisi nord americane sui musei e sulle politiche culturali. Questi studi, assumendo spesso uno sguardo postmoderno, hanno esplicitato il carattere politico e conflittuale del museo. Esso, infatti, è presentato come un'istituzione nella quale è possibile, se non proprio necessario, rappresentare in forme dialogiche e controllate le tensioni politiche e sociali che agitano lo spazio pubblico. Anche in una prospettiva postmoderna, l'istituzione museo conserva, però, il proprio carattere democratico di 'forum' pubblico. Questo scritto si chiede allora cosa accade quando lo spazio pubblico assume conformazioni inattese, meno strutturate rispetto a quelle nordamericane e radicalmente conflittuali.

Xenoi en Sicile dans la première moitié du Ve siècle (Diod. XI, 72,3)

Who were the xenoi frequently mentioned by Diodorus Siculus in his account of the revolt of the mercenaries in south-eastern Sicily around the middle of the Vth century B.C. ? Were they Greeks from other cities ? Or Barbarians ? One tries here to demonstrate, studying the peculiarities of certain grave goods of Gela, that these mercenaries were not Greeks, but Barbarians whose greater part had come from Campania since the beginning of the fifth century B.C.