Pantelleria Research Articles

Combined Sr-Nd isotopic and geochemical fingerprinting as a tool for identifying tephra layers: Application to deep-sea cores from Eastern Mediterranean Sea

Tephra layers from six deep-sea cores, recovered between the Ionian and the Aegean Seas, and covering a time span between ~102 and ~8.2ka BP, were investigated with the aim of identifying their volcanic source. The stratigraphic position of each tephra layer defined by means of nannofossil biostratigraphy and occurrence of sapropel layers was integrated with a thorough geochemical characterization of glass shards based on major oxides and trace elements content, and Sr-Nd isotope ratios. Major oxides composition permitted their subdivision into three groups (K-trachyte, peralkaline rhyolite, andesite), confirmed by Principal Component Analysis on trace elements data. Primordial mantle-normalized trace elements distribution patterns allowed for precise identification of the geochemical affinity and geodynamical setting of each group. Although the Sr isotopic composition of some investigated tephras was deeply affected by seawater alteration as expected, the 143Nd/144Nd values discriminate well the three groups of tephras in combination with major oxides and trace elements data. Therefore, La/Yb and Th/Y vs. 143Nd/144Nd discrimination diagrams are proposed for identification of potential volcanic sources active in the 102–8.2ka BP time span in the Eastern Mediterranean area for unknown tephras.The obtained results have permitted the attribution of six K-trachytic tephras to the Y-5 stratigraphic marker (Campanian Ignimbrite eruption of Campi Flegrei, Southern Italy, ~39ka BP), and two pantelleritic (=peralkaline rhyolite) tephras to the Y-6 stratigraphic marker (Green Tuff eruption of Pantelleria Island, Sicily Channel, ~46ka BP). The andesitic tephra, stratigraphically constrained between ~39 and ~83–102ka BP, might correspond to the X-1 stratigraphic marker, found in several deep-sea cores of the Eastern Mediterranean Sea, although its attribution is still debated in the literature. On the basis of trace elements content, supported by Sr-Nd isotopic features, it is here hypothesized that this tephra could be related to a volcanic source located in the Aegean Sea area, probably the island of Santorini. More generally, this study demonstrates that the combination of Sr-Nd isotopic with major oxide and trace element geochemical fingerprinting on selected and purified glass shards is a very effective tool for identifying nature and source of doubtful tephra layers.

Wind Patterns affect Migration Flyways and Flock Size of a Soaring Bird over Sea

Water surfaces are natural barriers for raptors mostly using soaring–gliding flight over land during migration. Among these, the European Honey Buzzard ( Pernis apivorus) is a total migrant, breeding in Europe and wintering in central western Africa. Each spring thousands of buzzards undertake long sea crossings between Tunisia and southern Italy, concentrating over small islands en route to central eastern Europe. The aim of this research is to investigate the influence of wind patterns on the flyways used by these raptors during this critical phase of migration through field observations at four small Mediterranean islands (Pantelleria, Marettimo, Ustica and Panarea) and at the Straits of Messina between 20 April and 20 May 2006–2013. In our analyses, peak days were considered for each site. This eight year multisite study allowed the collection of a large data set. While crossing the Channel of Sicily, migrants concentrated over Pantelleria (southern side of the Channel) during moderate NW winds, and over Marettimo (northern side) during weaker southerly winds. Over the island of Ustica (north-western Sicily, Tyrrhenian Sea) raptors were observed mostly with weak southerly winds. Over the island of Panarea (northeastern Sicily) and at the Straits of Messina, European Honey Buzzards passed with weak winds from W and NW, respectively. The average flock size during the peak days was significantly higher over the island of Pantelleria, where birds migrated during the stronger winds. The results of this study show that wind patterns affect both migration pathways and flocking behaviour of this species while crossing large water surfaces.

Structural characterization of the lipid A from the LPS of the haloalkaliphilic bacterium Halomonas pantelleriensis.

Halomonas pantelleriensis DSM9661(Τ) is a Gram-negative haloalkaliphilic bacterium isolated from the sand of the volcanic Venus mirror lake, closed to seashore in the Pantelleria Island in the south of Italy. It is able to optimally grow in media containing 3-15% (w/v) total salt and at pH between 9 and 10. To survive in these harsh conditions, the bacterium has developed several strategies that probably concern the bacteria outer membrane, a barrier regulating the exchange with the environment. In such a context, the lipopolysaccharides (LPSs), which are among the major constituent of the Gram-negative outer membrane, are thought to contribute to the restrictive membrane permeability properties. The structure of the lipid A family derived from the LPS of Halomonas pantelleriensis DSM 9661(T) is reported herein. The lipid A was obtained from the purified LPS by mild acid hydrolysis. The lipid A, which contains different numbers of fatty acids residues, and its partially deacylated derivatives were completely characterized by means of ESI FT-ICR mass spectrometry and chemical analysis. Preliminary immunological assays were performed, and a comparison with the lipid A structure of the phylogenetic proximal Halomonas magadiensis is also reported.

Exploring the submarine Graham Bank in the Sicily Channel

<p>In the Sicily Channel, volcanic activity has been concentrated mainly on the Pantelleria and Linosa islands, while minor submarine volcanism took place in the Adventure, Graham and Nameless banks. The volcanic activity spanned mostly during Plio-Pleistocene, however, historical submarine eruptions occurred in 1831 on the Graham Bank and in 1891 offshore Pantelleria Island. On the Graham Bank, 25 miles SW of Sciacca, the 1831 eruption formed the short-lived Ferdinandea Island that represents the only Italian volcano active in historical times currently almost completely unknown and not yet monitored. Moreover, most of the Sicily Channel seismicity is concentrated along a broad NS belt extending from the Graham Bank to Lampedusa Island. In 2012, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) carried out a multidisciplinary oceanographic cruise, named “Ferdinandea 2012”, the preliminary results of which represent the aim of this paper. The cruise goal was the mapping of the morpho-structural features of some submarine volcanic centres located in the northwestern side of the Sicily Channel and the temporary recording of their seismic and degassing activity. During the cruise, three OBS/Hs (ocean bottom seismometer with hydrophone) were deployed near the Graham, Nerita and Terribile submarine banks. During the following 9 months they have recorded several seismo-acoustic signals produced by both tectonic and volcanic sources. A high-resolution bathymetric survey was achieved on the Graham Bank and on the surrounding submarine volcanic centres. A widespread and voluminous gas bubbles emission was observed by both multibeam sonar echoes and a ROV (remotely operated vehicle) along the NW side of the Graham Bank, where gas and seafloor samples were also collected.</p>

Zirconium–hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water

Geochemical behaviour of rare earth elements (REE), Zr, and Hf was investigated in CO2-rich waters circulating in Pantelleria Island also including ‘Specchio di Venere’ Lake within a calderic depression. A wide range of total dissolved REE concentrations was found (2.77–12.07nmolL−1), with the highest contents in the lake. The main REE complexes in the CO2-rich waters are [REE(CO3)2]− and [REECO3]+, showing changeable proportions as a function of pH. The REE normalized to post-Archean Australian Shale (PAAS) showed similar features with heavy REE (HREE) enrichments in CO2-rich waters collected from springs and wells, whereas a different REE pattern was found in the ‘Specchio di Venere’ Lake water with middle REE (MREE) enrichments. The PAAS normalized concentration ratios (LREE/HREE)N and (MREE/HREE)N in waters are <1, except for the lake water in which (MREE/HREE)N>1. Positive Eu anomalies were found in the investigated waters owing to water–rock interactions with less evolved host rocks. Ce anomalies as a function of Eh values were recognized, with the highest Ce anomaly occurring in the lake water with respect to the CO2-rich waters. The Y/Ho and Zr/Hf molar ratios are higher in the investigated waters (except for lake water) than that in the local rocks, with values ranging from 35.4 to 77.9 and from 76.3 to 299, respectively. The precipitation of authigenic phases was considered to be responsible for the increase in the Y/Ho and Zr/Hf ratios owing to enhanced Hf and Ho removal with respect to Zr and Y.The REE patterns in the lake water show a similar shape (MREE-enriched and a positive Ce anomaly) as those found in the settling dust and in the desert varnish coating of the rocks in arid environments, which mainly contain Fe- and Mn-oxyhydroxides and clay minerals. Similarly, Y/Ho and Zr/Hf ratios in the ‘Specchio di Venere’ Lake (35.4 and 76.3, respectively) show a desert varnish signature. These data, coupled with the presence of iron oxyhydroxides and phyllosilicates in the shallowest water layer of the ‘Specchio di Venere’ Lake, verify the aeolian input from the Sahara Desert.

Models for the estimation of Fe3+/Fetotratio in terrestrial and extraterrestrial alkali- and iron-rich silicate glasses using Raman spectroscopyk

To develop Raman spectroscopy as a quantitative tool in both geosciences and planetary sciences the effect of iron oxidation state (Fe 3+ /Fe tot ) on the Raman spectra of basaltic and pantelleritic glasses has been investigated. We have used remelted pantellerite from Pantelleria Island and synthetic iron-rich basaltic glasses [from Chevrel et al. (2014)]. The Raman spectra of pantelleritic glasses reveal dramatic changes in the high wavelength region of the spectrum (800–1200 cm −1 ) as iron oxidation state changes. In particular the 970 cm −1 band intensity increases with increasing oxidation state of the glass (Fe 3+ /Fe tot ratio from 0.24 to 0.83). In contrast, Raman spectra of the basaltic glasses do not show the same oxidation state sensitivity (Fe 3+ /Fe tot ratio from 0.15 to 0.79). A shift, however, of the 950 cm −1 band to high wavenumber with decreasing iron oxidation state can be observed. We present here two empirical parameterizations (for silica- and alkali-rich pantelleritic glasses and for iron-rich basaltic glasses) to enable estimation of the iron oxidation state of both anhydrous and hydrous silicate glasses (up to 2.4 wt% H 2 O). The validation of the models derived from these parameterizations have been obtained using the independent characterization of these melt samples plus a series of external samples via wet chemistry. The “pantelleritic” model can be applied within SiO 2 , FeO, and alkali content ranges of ~69–75, ~7–9, and ~8–11 wt%, respectively. The “basaltic” model is valid within SiO 2 , FeO, and alkali content ranges of ~42–54, ~10–22, and ~3–6 wt%, respectively. The results of this study contribute to the expansion of the compositionally dependent database previously presented by Di Genova et al. (2015) for Raman spectra of complex silicate glasses. The applications of these models range from microanalysis of silicate glasses (e.g., melt inclusions) to handheld in situ terrestrial field investigations and studies under extreme conditions such as extraterrestrial (i.e., Mars), volcanic, and submarine environments.

Carbonate precipitation in the alkaline lake Specchio di Venere (Pantelleria Island, Italy) and the possible role of microbial mats

Alkaline lakes like the hydrothermally affected lake Specchio di Venere (Pantelleria Island, Central Mediterranean) are typical geological settings harbouring calcified microbial mats. The present work is focused on the discrimination between biotic and abiotic processes driving carbonate precipitation in this lake, using hydrochemical, mineralogical and isotopic data. Hydrochemical analyses demonstrate that the lake is nearly 10−fold supersaturated with regard to aragonite and seasonally reaches hydromagnesite supersaturation. Microscopic observations depict organosedimentary laminated structures consisting of microbial communities and aragonitic precipitates, which are rather disseminated in pores than directly linked to microorganisms. Oxygen isotopic data indicate that authigenic carbonate crystallisation from evaporating water is the dominant precipitation process, further suggested by the absence of textural evidence of diagenetic processes. Conversely, the observed δ13C values reflect an influence of extracellular polymeric substances (EPS) on carbon fractionation during the precipitation process, due to the selective sequestration of 12C in the biomass. The above considerations suggest that at lake Specchio di Venere the carbonate precipitation is mainly of inorganic nature, but a minor role played by biologically influenced processes in microbial mats is not excluded.

Archaeometric characterization of Roman volcanic millstones from Messina territory (Sicily, Italy)

In this paper we present the results of petrochemical study of Roman cereal millstones and relative elements made of volcanic rocks, found in various archaeological sites of Messina. Fifteen samples dating from the III century AD and one from the second, also dating from the II–III centuries AD, were characterized through archaeological, petrographic, mineralogical and geochemical approach. On the petrochemical point of view the raw materials of the studied millstones are mainlyvolcanic rock characterized by Na-alkaline affinity with intraplate geochemical signature. Only two samples belonging to the K-alkaline seires showing volcanic arc signature. Comparison with literature data of similar volcanic rocks, allowed to constrain the volcanic site of provenance. Most of the intraplate samples are mugearites and benmoreites from Mt. Etna, the other are peralkaline-trachyte from Pantelleria Island and alkaline basalt from Linosa Island. The two arc-type samples derived instead from Islands of the Aeolian Archipelago. The petrochemical study of millstones improve the archaeological research, confirming the ancient communication routes and trade networks in the Mediterranean Region and highlighted the use of volcanic rocks from Sicilian area, during the Roman period, as very important sources of raw materials for millstones.

Geochemical and Isotopic Characterisation of Actual Lacustrine Sediments from the Hydrothermal LakeSpecchio di Venere, Pantelleria Island (Italy)

Hydrothermal lakes are a very common feature in volcanic environments, and among these lake Specchio di Venere (Pantelleria island, Italy) has attracted the interest of several researchers due to its peculiar characteristics. With the aim of improving the knowledge of its mineralogy, our work pointed out the characterisation of the bottom lake sediments. We collected and analysed 5 sediments cores around the shoreline, determining the mineralogical phases, concentration of major, minor, and trace elements, and the isotopic composition of carbon and oxygen in the carbonate phases. Our findings remarked a general compositional homogeneity in both the vertical and horizontal distribution of mineral phases, with the exception of peculiar geological niches connoted by biological and hydrothermal activities.

The latest phase of the Bronze age settlement of Mursia in the north-western area of sector B

This paper deals with main results of investigations carried out since 2003 till 2013 in the north-western area of sector B, inside the Bronze Age settlement of Mursia (Pantelleria island), traditionally named Northern Area. The archaeological sequence belongs to the most recent phases of the settlement (XVI-XV cent.BC). The stratigraphic analysis and the evaluation of architectural remains allow to identify three main macro-phases with a lively settlement dynamics that include frequent and quick changes inside a continuous process of transformations. The abandonment of the settlement around the mid of XV cent.BC concludes the sequence. The analysis of plenty and diversified pottery production of these recent phases allowed to go in depth into the comprehension of the facies of Mursia with a proposal of recognition of representative types of the recent phases of the settlement.

Productivity analysis of the full scale inertial sea wave energy converter prototype: A test case in Pantelleria Island

Wave power is one of the most rich and promising sources of renewable energy for the future. Approximately 2000 TWh/year can be produced through the exploitation of the wave energy potential. In the past four decades, hundreds of Wave Energy Converters have been proposed and studied, but so far a conclusive architecture to harvest wave power has not been identified. Many engineering problems are still to be solved; these include survivability, durability, and effective power capture in a variable wave climate. Reacting body devices use the inertia of a large mass to generate the reaction needed from the power take off (PTO). Heretically, in the case of a simple inertial mass, optimal control adjusts the dynamic parameters of the PTO, such as the spring constant and energy absorbing damping, to maximize energy absorption. The ISWEC (Inertial Sea Wave Energy Converter) uses a gyroscope to create an internal inertial reaction that is able to harvest wave power without exposing mechanical parts to the harsh oceanic environment. In the past few years, the ISWEC has been successfully tested using two scale models (scales 1:45 and 1:8) and several extensive laboratory experimental campaigns. In this paper, the first full scale ISWEC prototype is presented along with its control system and a refined control strategy. The goal of this paper is to identify an optimal control strategy in order to maximize wave power exploitation of the ISWEC. The control technique presented is numerically applied to the ISWEC full scale device with rated power of 60 kW. The control strategy is tested, and the expected production obtained, for the typical wave climate of Pantelleria Island, in the Mediterranean Sea where the first full scale ISWEC prototype was deployed in autumn 2015.

Ground-penetrating radar survey on the island of Pantelleria (Italy) reveals an ancient architectural complex with likely Punic and Roman components

A ground-penetrating radar (GPR) survey conducted on the small volcanic island of Pantelleria, in the Strait of Sicily, south-central Mediterranean, revealed an apparent complex of Punic/Roman architecture. The survey focused on the Lago di Venere area, where a previously investigated ritual Punic site was built alongside a brackish volcanic lake. The site also exhibits evidence of earlier Eneolithic components and later Roman components. The full extent of the site has remained undetermined, however, with only the small area of the Punic ritual complex having been excavated from 1996 to 2002. The GPR survey was intended to explore whether additional architecture remained unseen in surrounding areas, thus taking a first step toward determining the site's full spatial extent and archaeological potential. This survey revealed a complex of architectural ruins beneath an active agricultural field immediately west of the previously excavated features, and extending to a depth of approximately 2m. These newly discovered features expand the known architectural footprint of the immediate site by three-fold. This GPR study is the first published archaeo-geophysical investigation on the island.

The implications of water storage for human settlement in Mediterranean waterless islands: The example of Pantelleria

Consistent water supply is a common issue in the history of Mediterranean civilizations, where hydraulic solutions, such as cisterns, wells, reservoirs and aqueducts, were adopted for private and public supply. In this context, the island of Pantelleria, where surface freshwater is virtually non-existent, represents a unique case for understanding human–environment interaction in waterless environments. Here, in historical times, year-round water supply was only possible through the storage of rainwater in underground cisterns. An intensive field survey carried out across the island led to the discovery of hundreds of cisterns dated from the Punic and Roman periods to the present day. The study of the spatial distribution of the cisterns was compared with archaeological data on the island to gain new insights on historical settlement and demographic patterns. The present work focusses on a semi-quantitative assessment of water storage on the island of Pantelleria based on the evaluation of potential volumes of stored water for different periods. Data available for cisterns in Pantelleria have been analysed and compared with those from coeval Mediterranean regions. Calculations on the seasonal fluctuation between water demand and supply have been estimated to evaluate the efficiency of such system for sustaining human population and subsistence activities through time.

Phenotypic and metabolic responses to drought and salinity of four contrasting lentil accessions.

Drought and salinity are among the major abiotic stresses which, often inter-relatedly, adversely affect plant growth and productivity. Plant stress responses depend on the type of stress, on its intensity, on the species, and also on the genotype. Different accessions of a species may have evolved different mechanisms to cope with stress and to complete their life cycles. This study is focused on lentil, an important Mediterranean legume with high quality protein for the human diet. The effects of salinity and drought on germination and early growth of Castelluccio di Norcia (CAST), Pantelleria (PAN), Ustica (UST), and Eston (EST) accessions were evaluated to identify metabolic and phenotypic traits related to drought and/or salinity stress tolerance. The results showed a relationship between imposed stresses and performance of the cultivars. According to germination frequencies, the accession ranking was as follows: NaCl resistant > susceptible, PAN > UST > CAST > EST; polyethylene glycol (PEG) resistant > susceptible, CAST > UST > EST > PAN. Seedling tolerance rankings were: NaCl resistant > susceptible, CAST ≈ UST > PAN ≈ EST; PEG resistant > susceptible, CAST > EST ≈ UST > PAN. Changes in the metabolite profiles, mainly quantitative rather than qualitative, were observed in the same cultivar in respect to the treatments, and among the cultivars under the same treatment. Metabolic differences in the stress tolerance of the different genotypes were related to a reduction in the levels of tricarboxylic acid (TCA) cycle intermediates. The relevant differences, between the most NaCl-tolerant genotype (PAN) and the most sensitive one (EST) were related to the decrease in the threonic acid level. Stress-specific metabolite indicators were also identified: ornithine and asparagine as markers of drought stress and alanine and homoserine as markers of salinity stress.

Tracing formation and durability of calcite in a Punic–Roman cistern mortar (Pantelleria Island, Italy)

Ancient hydraulic lime mortar preserves chemical and isotopic signatures that provide important information about historical processing and its durability. The distribution and isotopic composition of calcite in a mortar of a well-preserved Punic–Roman cistern at Pantelleria Island (Italy) was used to trace the formation conditions, durability, and individual processing periods of the cistern mortar. The analyses of stable carbon and oxygen isotopes of calcite revealed four individual horizons, D, E, B-1 and B-2, of mortar from the top to the bottom of the cistern floor. Volcanic and ceramic aggregates were used for the production of the mortar of horizons E/D and B-1/B-2, respectively. All horizons comprise hydraulic lime mortar characterized by a mean cementation index of 1.5 ± 1, and a constant binder to aggregate ratio of 0.31 ± 0.01. This suggests standardized and highly effective processing of the cistern.The high durability of calcite formed during carbonation of slaked lime within the matrix of the ancient mortar, and thus the excellent resistance of the hydraulic lime mortar against water, was documented by (i) a distinct positive correlation of δ18Ocalcite and δ13Ccalcite; typical for carbonation through a mortar horizon, (ii) a characteristic evolution of δ18Ocalcite and δ13Ccalcite through each of the four mortar horizons; lighter follow heavier isotopic values from upper to lower part of the cistern floor, and (iii) δ18Ocalcite varying from −10 to −5 ‰ Vienna Pee Dee belemnite (VPDB). The range of δ18Ocalcite values rule out recrystallization and/or neoformation of calcite through chemical attack of water stored in cistern.The combined studies of the chemical composition of the binder and the isotopic composition of the calcite in an ancient mortar provide powerful tools for elucidating the ancient techniques and processing periods. This approach helps to evaluate the durability of primary calcite and demonstrates the importance of calcite as a proxy for chemical attack and quality of the ancient inorganic binder.

The Hyblean xenolith suite (Sicily): an unexpected legacy of the Ionian–Tethys realm

The extensive study of a great number of deep-seated xenoliths from Tortonian tuff-breccia pipes in the Hyblean area (Sicily) revealed the following fundamental evidence: (1) typical continental crust rocks are completely absent in the entire xenolith suite; (2) mantle ultramafics are more abundant than gabbroids; (3) sheared oxide–gabbros, closely resembling those from oceanic fracture zones, are relatively common; (4) secondary mineral assemblages, compatible with alteration processes in serpentinite-hosted hydrothermal systems, occur both in peridotites and gabbros. Among the products of this hydrothermal activity, organic compounds, having abiotic origin via Fischer–Tropsch synthesis, occur in some hydrothermally altered gabbro and ultramafic xenoliths, as well as in hydrothermal clays. Moreover, the U–Pb dating of hydrothermal zircon grains, hosted in a xenolith of metasomatized tectonic breccia, indicated an Early–Middle Triassic age of the fossil hydrothermal system. Another line of evidence for the oceanic nature of the Hyblean–Pelagian basement is the complete absence of continental crust lithologies (granites, felsic metaigneous, and metasedimentary rocks) in outcrops and in boreholes, and the oceanic affinity of the Tertiary volcanic rocks from the Hyblean Plateau and the Sicily Channel (Pantelleria and Linosa Islands), which lack of any geochemical signature for continental crust contamination. A reappraisal of existing geophysical data pointed out that serpentinites form the dominant lithologies in the lithospheric basement of the Hyblean–Pelagian area down to a mean depth of 19 km, which represents the regional Moho considered as the serpentinization front, marking the transition from serpentinites to unaltered peridotites. On these grounds, we confirm that Hyblean xenoliths contain mineralogical, compositional, and textural evidence for tectonic, magmatic, and hydrothermal processes indicating the existence of fossil oceanic core complexes, in the geotectonic framework of the Paleo–Mesozoic, ultra-slow spreading, Ionian–Tethys Ocean forming the present Ionian–Hyblean–Pelagian domain.

Agronomical evaluation of Sicilian biotypes of Lavandula stoechas L. spp. stoechas and analysis of the essential oils

The aim of this study was to characterize wild lavender, which was collected in three different areas of Sicily (Italy), according to agronomic and chemical evaluation. The collection sites were located in Pantelleria island, Partinico (a warm sub-area of Lauretum) and Castelbuono (a middle sub-area of Lauretum). All the populations were identified as Lavandula stoechas L. ssp. stoechas. Essential oils were extracted by hydrodistillation and analyzed by gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (GC–MS). GC–FID and GC–MS analyses permitted the identification of 101 components from the essential oils. We analyzed only the flowers and leaves of L. stoechas and the samples were analyzed using the PCA (principal component analysis) methodology regarding the chemical composition of the essential oils. Comparisons were carried out between the chemical compositions of essential oils from Sicilian populations and other Mediterranean populations. The essential oils of Sicilian L. stoechas biotypes were fenchone chemotype with percentages ranging from 45.29% to 60.27%. The qualitative chemical composition of the essential oils varied according to the different areas of origin of the plant material. Sicilian biotypes of L. stoechas showed high differences in chemical composition compared with the populations coming from other Mediterranean areas.

Marine geological and archaeological evidence of a possible pre-Neolithic site in Pantelleria Island, Central Mediterranean Sea

Abstract Recent underwater archaeological surveys recovered hundreds of flint artefacts between depths of 18 and 21 m at Cala Tramontana, a small bay located in the eastern part of Pantelleria Island. Most of the flint artefacts indicate debitage, and are characterized by cores and flakes without any specific morphology. Different lithic tools were also identified, such as fragments of blades, truncations, end-scrapers, points and crested blades. An initial hypothesis is that this lithic industry represents the oldest traces of human visitation to the island, possibly related to the exploitation of the nearby obsidian source, and favoured because of the sheltered coastal configuration of Cala Tramontana and Cala Levante with respect to the dominant winds and related storms. However, the present-day coastal setting in the bay is rather inhospitable, with high cliffs and difficult marine access. In contrast, palaeo-landscape reconstructions by means of high-resolution multibeam bathymetry reveal the possible presence of a small palaeo-beach in the inner part of the bay when the sea level was 15 m lower than at present. By comparing this palaeo-sea level with the eustatic curve (and by excluding possible vertical movements), we roughly estimate an age of the lithic industry of 9.6–7.7 cal ka BP.

Obsidians from the Kerkennah Islands (eastern Tunisia) and the PIXE elemental compositions of the Mediterranean peralkaline obsidians

The provenance of 37 obsidians from the Kerkennah Islands (central Mediterranean Sea) was determined by PIXE. It is shown that they came from the two main obsidian sources, Balata dei Turchi and Lago di Venere, of the Pantelleria Island. A comparison of the PIXE elemental composition of geological vs. archaeological obsidians of central and western Mediterranean shows that their sources present elemental compositions homogeneous enough to make possible sourcing studies. However, a comparison between the distributions of geological and archaeological obsidians chemistry shows that the PIXE source qualifications do not cover yet the whole of their internal variations.

Exploration of the 1891 Foerstner submarine vent site (Pantelleria, Italy): insights into the formation of basaltic balloons

On October 17, 1891, a submarine eruption started at Foerstner volcano located within the Pantelleria Rift of the Strait of Sicily (Italy). Activity occurred for a period of 1 week from an eruptive vent located 4 km northwest of the island of Pantelleria at a water depth of 250 m. The eruption produced lava balloons that discharged gas at the surface and eventually sank to the seafloor. Remotely operated vehicle (ROV) video footage and high-resolution multi-beam mapping of the Foerstner vent site were used to create a geologic map of the AD 1891 deposits and conduct the first detailed study of the source area associated with this unusual type of submarine volcanism. The main Foerstner vent consists of two overlapping circular mounds with a total volume of 6.3 × 105 m3 and relief of 60 m. It is dominantly constructed of clastic scoriaceous deposits with some interbedded pillow lavas. Petrographic and geochemical analyses of Foerstner samples by X-ray fluorescence and inductively coupled plasma mass spectrometry reveal that the majority of the deposits are vesicular, hypocrystalline basanite scoria that display porphyritic, hyaloophitic, and vitrophyric textures. An intact lava balloon recovered from the seafloor consists of a large interior gas cavity surrounded by a thin lava shell comprising two distinct layers: a thin, oxidized, quenched crust surrounding the exterior of the balloon and a dark gray, tachylite layer lying beneath it. Ostwald ripening is proposed to be the dominant bubble growth mechanism of four representative Foerstner scoria samples as inferred by vesicle size distributions. Characterization of the diversity of deposit facies observed at Foerstner in conjunction with quantitative rock texture analysis indicates that submarine Strombolian-like activity is the most likely mechanism for the formation of lava balloons. The deposit facies observed at the main Foerstner vent are very similar to those produced by other known submarine Strombolian eruptions (short pillow flow lobes, large scoriaceous clasts, spatter-like vent facies). Balloons were likely formed from the rapid cooling of extremely vesicular magma fragments as a result of a gas-rich frothy magma source. The exterior of these fragments hyperquenched forming a vesicular glassy shell that acted as an insulating layer preventing magmatic gas in its interior from escaping and thus allowing flotation as densities reached less than 1,000 kg/m3. We believe that lava balloons are a common eruptive product, as the conditions required to generate these products are likely to be present in a variety of submarine volcanic environments. Additionally, the facies relationships observed at Foerstner may be used as a paleoenvironmental indicator for modern and ancient basaltic shallow submarine eruptions because of the relatively narrow depth range over which they likely occur (200–400 m).