NW Sardinia Research Articles

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As part of a collaborative project to investigate human impacts on Quercus suber L. (cork oak) forests, five research groups from countries in Europe and North Africa undertook a survey of soil quality (physical properties, potentially toxic elements) at sites in NW Tunisia and NW Sardinia. All groups performed the analysis of soil samples after agreeing prescribed methodologies to ensure harmonisation and the production of a robust and reliable data set. The data produced were compared using basic statistical methods and revealed strong positive correlation despite minor operational variation. The data indicates that inter and intra laboratory variability differed from parameter to parameter and that good agreement was obtained where methodology was common. Collaborative research introduced the need for common communication plans and exchange of information not normally supplied in analytical reporting. Key words: Forest soil quality, inter-comparison, Quercus suber L., cork oak, Tunisia, Sardinia, chemical analysis, potentially toxic elements.

Effects of laying power cables on a Posidonia oceanica (L.) Delile prairie: the study case of Fiume Santo (NW Sardinia, Italy)

ABSTRACT Bacci T., Rende F.S., Nonnis O., Maggi C., Izzi A., Gabellini M., Massara F., Di Tullio L., 2013. Effects of laying power cables on a Posidonia oceanica (L.) Delile prairie: the study case of Fiume Santo (NW Sardinia, Italy). Coastal areas are complex systems where both marine ecosystems and human activity interrelate, often raising several conflicts. The economic activities may, sometimes, disturb the functioning and stability of coastal ecosystems, particularly of the seagrass meadows, and menace their future existence. In the Mediterranean Sea the most important seagrass is Posidonia oceanica (L.) Delile, an endemic species, which meadows have been defined priority habitats following the 92/43/CEE Directive. Therefore, all technical solutions for cables or pipelines installation across a P. oceanica prairie should be adapted in order to protect these ecosystems and to prevent their degradation allowing the maintenance of a satisfactory state of conservation. In this work we present the results...

Ordovician Albitites Generated by Magmatic Fluids within a Volcano-Sedimentary Sequence from NW Sardinia

Two albitite layers were discovered near Lula village within a volcano-sedimentary sequence of likely Ordovician age in the Internal Nappe Zone (NE Sardinia). The albitites consist of up to 95% albite, with small amounts of quartz, biotite, chlorite, Fe-oxides, apatite, and monazite. They are the first albitites to be found in NE Sardinia, and the first known case of Ordovician albitites. In central and southern Sardinia the albitites occur as late Variscan dykes and small intrusions. The albitization process is attributed to hydrothermal fluids produced during the late stages of middle Ordovician volcano-plutonic activity. A comparison of the albitite compositions with the non-albitized samples reveals that albitites are characterized by strong gains of Na, slight gains of Al, Si, and Sr, and remarkable losses of K, Rb, Ba, Ca, Mg, Fe, Ti, Ni, and V. These albitites are also enriched in LREE and depleted in HREE.

New Mediterranean Biodiversity Records (December 2012)

This paper presents records extending or confirming the distribution of Mediterranean species. Three alien algae are included, namely Codium taylorii reported for the first time from the Aegean and Turkey (Izmir Gulf), Caulerpa racemosa var. cylindracea (Karpathos and Chalki Isl., Aegean Sea) and Ganonema farinosum (Karpathos Isl., Aegean Sea). As far as animals are concerned, Litarachna divergens (Acari: Hydrachnidia) was recorded (Side, Eastern Mediterranean) and represents a new amendment at genus level for Turkish fauna. Other invertebrates include alien species such as the crabs Dyspanopeus sayi (Lago Fusaro, SW Italy), Percnon gibbesi (Larnaca, Cyprus; Karpathos and Chalki Isl., Aegean Sea) and Callinectes sapidus (Voda estuary, NW Greece), the nudibranch Aplysia dactylomela (Boka Kotorska Bay, Montenegro), the gastropod Conomurex persicus (Karpathos and ChalkiIsl., Aegean Sea) and the bryozoan Electra tenella (Livorno harbour and Messina Straits area). The alien fish Siganus luridus, Siganus rivulatus, Fistularia commersonii, Sphyraena chrysotaenia and Sargocentron rubrum are also reported from the islands of Karpathos and Chalki, and Pteragogus pelycus from Heraklion Bay, Crete. In addition, new localities for four rare Mediterranean inhabitants are given: the cephalopod Thysanoteuthis rhombus (NW Sardinia) and the fish: Lampris guttatus (Calabria, S Italy), Petromyzon marinus (Gokova Bay) and Remora australis (Saronikos Gulf), while the opisthobranch gastropod Cerberilla bernadettae is reported for the first time from the E Mediterranean (Cyprus). Finally, three species of the Aegean ascidiofauna are recorded for the first time: Lissoclinum perforatum, Ciona roulei and Ecteinascidia turbinata. Furthermore, it was established that Phallusia nigra has extended its distributional range to the north of the Aegean Sea.

Decoding sea level changes in western Mediterranean using speleothem encrustations from coastal caves in Mallorca and NW Sardinia

Along the eastern coast of Mallorca, many littoral caves partly filled with brackish waters occur. The most peculiar aspect of these caves is the presence of abundant phreatic overgrowths formed on pre-existing supports located at the underground pools' water table, which corresponds to the present sea level. Besides a specific geomorphological interest, these subaqueous speleothems provide an excellent record of Quaternary sea level stands. The clear relation between phreatic speleothem growth and the contemporary sea level allows the control of the tectonic evolution of an area, by comparing speleothems’ ages and heights with the regionally established eustatic curves. In the studied region different altimetric positions of coeval phreatic speleothems suggest the existence of a recent tectonic activity. The characteristics and chronology of this tectonic event are the objectives of this paper, pointing out at the same time the potential of phreatic speleothems in structural geology investigations. Along the coastline of the studied area, alignments of phreatic speleothems attributed to high sea stands 5a, 5c and 5e are recorded at increasing elevations northwards. This is an evidence of a significant tectonic tilting that took place, at least partially, after substage 5a because phreatic speleothems of this substage are now located at different altitudes. Considering that tectonic tilting has been continuous from post-substage 5a (approximately 85 ka) until now, and that normal displacement is approximately of 1.5 m, the average minimum velocity of the tilting can be estimated about 0.02 mm/year in the southern part with respect to the north end. Data obtained from phreatic speleothems have been compared with other regional, stratigraphical, geomorphological and tectonic evidence that all together point to the same existence of the postulated tectonic tilting. Consequently, phreatic speleothem investigation results in a new method that allows the quantification of average velocities of tilting as well as other tectonic movements with high precision. This methodology can be extended to any littoral karstic landscape where phreatic speleothems are present.

Alluvial, aeolian and tidal deposits in the Lower to Middle Triassic “Buntsandstein“ of NW Sardinia (Italy): a new interpretation of the Neo-Tethys transgression

Alluvial, aeolian and tidal deposits in the Lower to Middle Triassic “Buntsandstein“ of NW Sardinia (Italy): a new interpretation of the Neo-Tethys transgression

Definition of the European Lepidocyrtus curvicollis group (Collembola: Entomobryidae) with description of a new species from Sardinia (Italy)

The genus Lepidocyrtus was up to now represented by two species in Sardinia. However, recent molecular data suggestthe existence of several other species in the region. The study of a Lepidocyrtus population from the peninsula of CapoCaccia (NW Sardinia) has allowed the description of the species Lepidocyrtus apicalis sp. nov. Along with seven otherEuropean species, the new species constitute the “Lepidocyrtus curvicollis group”, characterized by the presence of scaleson the antenna, legs and dorsal side of manubrium, by having the mesothorax more or less protruded, labial seta M 1 shorterthan M 2 , presence of seta s on abd.IV, and by the dorsal macrochaetae formula R 0 R 1s R 1 So/00/0101+3. An identificationkey has been developed for differentiating all species of this group. With the new species the number of Lepidocyrtus species present in Sardinia increases to three and the number of total European Lepidocyrtus species to 30.

Analysis of salinization processes in the coastal carbonate aquifer of Porto Torres (NW Sardinia, Italy)

The Porto Torres (NW Sardinia) coastal aquifer is hosted in the carbonate rocks of the Miocene succession, which fills a NNW oriented half-graben. This aquifer is an important contributor to the fresh water supply of the local area. It is increasingly being degraded by salinization processes, mainly associated with intense groundwater over-exploitation. A combined hydrochemical and hydrogeological study has been carried out to identify the origin of the salinity in the groundwater. The behavior of the major ions showed that the changes in the chemical composition of the groundwater have been mainly controlled by the encroachment of seawater, accompanied by cation exchange reactions. Since seawater intrusion is a dynamic process, an Hydrochemical Facies Evolution Diagram, HFE-D (Gimenez Forcada, 2010) approach was taken to establish whether the aquifer was in the seawater intrusion or in the freshening phase. The assessment model developed provides regional authorities with a basic tools for sustainable water management in the framework of multi-disciplinary research activities aiming to combat and/or mitigate desertification and land degradation processes.

A Huge Caseid Pelycosaur from North-Western Sardinia and Its Bearing on European Permian Stratigraphy and Palaeobiogeography

Skeletal remains, some loose on the surface and others still embedded, have been recovered from the uppermost part of an outcrop of the Permian Cala del Vino Formation located near Torre del Porticciolo (Alghero, Nurra, NW Sardinia). Taphonomic analysis suggests that all the elements pertain to a single individual; ongoing studies indicate the fossil represents a large caseid close (or referable) to Cotylorhynchus; otherwise restricted to a narrow geographic and stratigraphic zone of the central USA. The new finding, the first of a caseid in Italy and one of few in Europe, enlarges the known distribution of the family and provides a significant and key chronostratigraphic constraint for the continental succession of this area and, in turn, helps establish a stratigraphic framework for the Permian units cropping out in Italy and southern France.

Messinian palaeoclimate and palaeo-environment in the western Mediterranean realm: insights from the geochemistry of continental deposits of NW Sardinia (Italy)

To evaluate the palaeo-environmental parameters of a portion of the Sardinia–Corsica microplate during the Messinian drop in sea level, we examined the chemistry and mineralogy of upper Tortonian–lower Messinian (late Miocene) clayey continental deposits from NW Sardinia. Differences exist between the uppermost part of the succession, which is devoid of carbonate phases, and the lower part, reflecting changes in provenance and climate. The carbonate-free samples were probably derived from quartzite of the metamorphic basement and were deposited under a climate characterized by alternating dry and relatively wet periods. The other samples were derived from basement phyllite and were deposited under a warm, dry climate that promoted the capillary rise of Ca2+ and bicarbonate from a shallow water table, and therefore, the precipitation of carbonate. This part of the succession contains both calcite and dolomite. The presence of barite indicates an important concentration of SO4 2− in the solution from which the CaMg(CO3)2 precipitated. The formation of dolomite under hypersaline conditions may be explained by bacterial degradation of organic matter, which produced CO2 and ammonia, thereby increasing the solution alkalinity. The succession formed in an oxic environment, except for a calcite-rich level that formed under relatively reducing conditions. For this level, the large amount of calcite and the lack of dolomite indicate an alkaline environment and a very low Mg2+/Ca2+ ratio in the soil solution. These observations, coupled with the reducing conditions, indicate the availability of large amounts of degraded organic matter, probably related to a period typified by a wetter climate.

Transgressive dune formation along a cliffed coast at 75 ka in Sardinia, Western Mediterranean: a record of sea-level fall and increased windiness

Transgressive dunes develop frequently along strandplain coastlines; however, they may also form along rocky coasts dominated by cliffs and embayments. Two lithified transgressive dune systems developed along the cliffed Alghero coast (NW Sardinia, Italy) have been investigated. One aeolian system forms a cliff-front anchored aeolian dune accumulation; the other is a valley-head anchored sand-ramp system. Optically stimulated luminescence ages indicate that both systems formed around 75 ka. This period, which corresponds to the beginning of MIS 4, was characterized by a relatively low sea-level stand (15 m below the present sea level) and was preceded by a sea-level highstand (+1 m asl) around 81 ka (MIS 5a). Our results show that this rapid sea-level fall exposed an enormous amount of marine sand, which was transported inland by strong northerly winds and deposited in front of cliffs or in valley heads. Therefore, sediment supply and sea-level fall seem to be critical factors controlling dune formation along rocky coasts, which generate time-transgressive aeolianites. Terra Nova, 00, 000–000, 2010

Sustainable Water Resources Management to Combat Desertification in the Nurra Region, Northwestern Sardinia, Italy

Sustainable water management plays an important role in the frame of the multidisciplinary research activities aiming to combat or to mitigate the desertification processes. The study activities have been carried out by RIADE Research Project (Integrated Research for Applying new technologies and processes for combating Desertification,www.riade.net). RIADE was co-financed by MIUR within the National Operative Programme 2000-2006. The primary objective was to explore and to develop models and strategies for innovative and sustainable solutions of water resources management, adopting a multidisciplinary approach, at the catchment and hydrogeological basin scale in a Mediterranean context, using a case history of a pilot area in NW Sardinia (Italy). The high concentration of population in this coastal zone and the intense agricultural activity have determined a relevant increase of water demand. This demand is generally satisfied by surface water, but, in some peculiar dry periods, it exceeds the available quantities. In these critical periods, groundwater are the only alternative source constituting a strategic water resource. The groundwater chemical properties are then correlated with the effects of the anthropogenic pressures. The used approach shows the application of groundwater protection criteria, in accordance with EU policies, and it was aimed to develop a methodological tool which can be applied to different scenarios.

From ramp to platform: building a 3D model of depositional geometries and facies architectures in transitional carbonates in the Miocene, northern Sardinia

The depositional geometry and facies distribution of an Early Miocene (Burdigalian) carbonate system in the Perfugas Basin (NW Sardinia) comprise a well-exposed example of a transition from a ramp to a steep-flanked platform. The carbonate succession (Sedini Limestone Unit) is composed of two depositional sequences separated by a major erosional unconformity. The lower (sequence 1) records a ramp dominated by heterozoan producers and the upper (sequence 2) is dominated by photozoan producers and displays a gradual steepening of the depositional profile into a steep-flanked platform. This paper shows the process of creating a digital outcrop model including a facies model. This process consists of combining field data sets, including 17 sedimentary logs, and a spatial dataset consisting of differential global positioning system data points measured along key stratigraphic surfaces and sedimentary logs, with the goal of locking traditional field observations into a 3D spatial model. Establishing a precise geometrical framework and visualizing the overall change in the platform geometry and the related vertical and lateral facies variations of the Sedini carbonate platform, allows us to better understand the sedimentary processes leading to the geometrical turn-over of the platform. Furthermore, a detailed facies modeling helps us to gain insight into the detailed depositional dynamics. The final model reproduces faithfully the depositional geometries observed in the outcrops and helps in understanding the relationships between facies and architectural framework at the basin scale. Moreover, it provides the basis to characterize semiquantitatively regional sedimentological features and to make further reservoir and subsurface analogue studies.

Mineralogical Characteristics and Cationic Exchange Properties of a Zeolite Mineral from Romana, NW Sardinia, Italy

AbstractAn investigation was conducted into the Tertiary ignimbrite formations in the Romana area in NW Sardinia. Scanning electron microscopy–energy‐dispersive spectrometry indicated the presence of clinoptilolite and subordinate smectite, quartz, mordenite and calcite. Laboratory analyses of representative samples collected from the deposit indicated a cation exchange capacity ranging from 85 to 135 mEq per 100 g. Ion exchange experiments conducted in flasks containing different initial cation concentrations and in columns supplied with solution having constant cation concentration, showed different selectivity towards the cations examined, in the order: NH4+> Pb2+> Cd2+> Cu2+> Zn2+> Mn2+> Ni2+. Compared to the untreated material, under the experimental conditions used and considering the eluate, and the Italian regulatory limits for discharge into surface waters, the zeolite treated with a 1‐N NaCl solution yielded a 1.3–5‐fold increase in the volume of treated water, depending on the cation examined. The experimental results obtained show that the cationic exchange properties of the zeolite rock from the Romana deposit are comparable with the average quality of zeolites currently imported into Italy from non‐European countries.

Shallow water sea-floor morphologies around Asinara Island (NW Sardinia, Italy)

Side scan sonar, high-resolution seismic and multibeam data collected off the coast of Asinara Island in the northernmost part of Sardinia have revealed the occurrence of four distinct acoustical patterns that can be related to four main sea-bed types. The four facies represent fine sand (Type A), medium to coarse sand (Type B), patchy sand cover between basement outcrops (Type C) and a predominantly sandy sea-floor colonized by the seagrass Posidonia Oceanica (Type P). The distribution of the sea-bed types indicates that the study area is characterized by a rather complex morphological setting. A remarkable physiographic difference exists between the eastern and western sector of the island, with the latter being affected by strong, westerly winds, mainly the so-called “Mistral”. The wave climate in this area is dominated by wind waves, which can reach a maximum height of 8 m during winter storms. Sediments are mobilized at water depths greater than 30 m from the sea surface during these energetic oceanographic regimes. We infer that dune fields and sand ribbons are deposited by strong offshore flows along the sea-bed resulting as a consequence of wave- and wind-induced onshore water transport.

Small-scale perturbation on soft bottom macrozoobenthos after mechanical cleaning operations in a Central-Western Mediterranean lagoon

1 - Sardinia Island (Italy), even if relatively small, has over 100 lagoons totalling some 12,000 ha. Yet their potential yield remain often unexpressed because they are subjected to environmental stress and degradation. As far as benthic communities are concerned, one of the main disturbances is certainly the accumulation of shell detritus, which progressively modifies the way benthic organisms interact with the sediment. 2 - An experimental dredging study was therefore performed in the Calich lagoon (NW Sardinia), due to its particular interest for fishing activities and potential semi-intensive mollusc culture. Changes in benthic community structure were examined in two areas of the lagoon by analysing both the demographic profile of several abundant species and the features of sedimentary matrix immediately after the cleaning operations and seven months later. Data obtained were compared with those collected in undisturbed areas of the lagoon. This allowed us to evaluate the effects of dredging operations on the benthic assemblages unaffected by natural temporal shifts of the system. 3 - Univariate and multivariate analyses indicated a strong relationship between macrofaunal community structure and intensity of the cleaning activities. At the dredged sites benthic fauna was not depleted but did exhibit higher diversity and evenness indexes than at the undisturbed sites. This seemed to be a consequence of decrease in the density of some abundant species at the dredged sites. Furthermore, a general reduction of total organic content was observed in the upper sediment layer. Lastly, the cleaning method employed is discussed in relation to its potential for impacting the benthos.

New biological data on Raja brachyura (Chondrichthyes, Rajidae) from around Asinara Island (NW Sardinia, Western Mediterranean)

A monitoring survey on the artisanal fishery of the Asinara Island (NW Sardinia, Western Mediterranean) provided a unique opportunity to improve our biological knowledge of the blonde ray (Raja brachyura), a skate species which is rare along Mediterranean coasts. A total of 225 specimens of R. brachyura were sampled in spring 2002 and analysed in order to characterise the species in terms of reproduction, feeding habits and structure of the local population. The results enabled us to gain an insight into the ecological features of the blonde ray, including its predation on Gymnammodytes cicerellus, the Mediterranean sand‐eel, a small‐size fish, typical of sandy‐gravel sea beds of the Mediterranean shelf.

Geological, geochemical and mineralogical features of some bauxite deposits from Nurra (Western Sardinia, Italy): insights on conditions of formation and parental affinity

Bauxite deposits are widespread in NW Sardinia. They formed during the middle Cretaceous, in consequence of a period of emergence of the Mesozoic carbonate shelf. In the Nurra area the geometries derived by the Middle Cretaceous tectonic phases controlled the ore typologies. Two bauxite profiles, laying on different bedrocks, were sampled. The bauxitization proceeded from the surface downward, with the accumulation of Al2O3 and residual ‘immobile’ elements (Al, Ti, HFSE), and corresponding mobility and loss of SiO2 and Fe2O3. Epigenetic kaolinite formed close to faults and joints, probably as a result of silicification, introduced by low temperature hydrothermal solutions. Rare earth elements, especially LREE, are concentrated in Fe-rich bauxite horizons, probably due to scavenging by goethite. REE-enrichment is not observed in the boehmite-rich horizons. Very high REE contents are observed in a Fe-depleted horizon due to the occurrence of REE accessory minerals, probably of the bastnasite group. Conservative indices, including TiO2/Al2O3 and Ti/Cr ratios, and Eu anomalies (Eu/Eu*), suggest that the deposits formed by weathering of sediments derived from mafic rocks of the Hercynian basement. This, in turn, implies that the basement was exposed during middle Cretaceous.

Optimizing interpolation of shoot density data from aPosidonia oceanicaseagrass bed

AbstractA case study on the optimization ofPosidonia oceanicadensity interpolation, using a data set from a large meadow at Porto Conte Bay (NW Sardinia, Italy), is presented. Ordinary point kriging, cokriging and a weighted average based on inverse square distance were used to interpolate density data measured in 36 sampling stations. The results obtained from different methods were then compared by means of a leave‐one‐out cross‐validation procedure. The scale at which interpolation was carried out was defined on the basis of the Hausdorff dimension of the variogram. Optimizing spatial scale and data points search strategy allowed obtaining more accurate density estimates independently of the interpolation method.

Northernmost occurrence of the offshore rockfish, Pontinus kuhlii (Scorpaeniformes: Scorpaenidae), in the Mediterranean Sea

An adult male specimen of the offshore rockfish, Pontinus kuhlii (Bowdich, 1825), was caught off the coast of Alghero (NW Sardinia, Italy) in August 2004. That capture represents the second documented record of this Atlantic migrant in Italian waters, after more than a century from the first report. Furthermore, the new specimen is the largest specimen of this species ever recorded in the Mediterranean Basin and the most northern capture for this geographic area. Morphologic and meristic characters of the collected fish are described and the existence of a Mediterranean population is hypothesized.