Eastern Liguria Research Articles

Mineralogical and geochemical spatial analyses of a waste-rock dump at the Libiola Fe–Cu sulphide mine (Eastern Liguria, Italy)

In this work, we investigated a 3 ha sulphide-bearing waste-rock dump (Libiola Mine, Italy) using mineralogical, geochemical, and geostatistical analyses. The dumped materials were highly heterogeneous in grain size and lithology and varied both laterally and vertically. Other than the host rock of the ore, basalts and serpentinites, the dumped materials contained high amounts of low-grade chalcopyrite- and pyrite-rich mineralisations. Due to these characteristics and to the absence of minerals able to neutralise acidity, this waste-rock dump can be classified as an acid mine drainage (AMD) producer. The study confirms that AMD is still active and, in the best scenario, can persist for up to 6.17 × 103 years. The consequences of this process are of serious environmental concern as it involves strong acidification of the circulating waters, the release of potentially toxic metals into the soil, streams and rivers and the precipitation of huge quantities of secondary Fe-oxides and Fe-oxyhydroxides.

Lago di Bargone, Liguria, N Italy: a reconstruction of Holocene environmental and land-use history

Sediment micromorphology, chemistry and magnetic susceptibility of basin edge deposits at the small, mid-altitude peat site of Lago di Bargone, eastern Liguria, Italy, is compared with a full Holocene palynological sequence and radiocarbon dates from the central part of the peat bog. Micromorphology and MS550 results show that Neolithic to Copper Age forest disturbances and clearings as inferred from the pollen diagrams, occurred during a period of lower water-tables and intermittent drying out of the basin edge deposits. Extensive deforestation and expansion of heath and grassland during the Iron Age and Roman periods is associated with increases in soil erosion and in micromorphological indications of burning. It is argued that the very fine size range of the charred fragments seen in thin sections and the seeming absence of charcoal of coarser size range suggest a system of light, controlled burning, possibly akin to the local tradition of using fire to control weeds and to encourage new grass and herbaceous growth, and not local forest clearance by fire. Micromorphology of the late-Holocene peat contains herbivore dung possibly indicating the use of the site as a watering hole by domesticated stock. The overlying colluvium displays evidence of deep-seated erosion of the local soils and geology which is most likely to have been associated with local mining activities.

Traditional uses of plants in the Eastern Riviera (Liguria, Italy)

Aim of the study The aim of the present study was to explore the traditional plant knowledge of a zone of the Ligurian coast, known as Riviera spezzina (RS), Eastern Liguria, Italy. Materials and methods Ethnobotanical information was obtained through open informal interviews. The informants were residents, belonging to families living in the study area since generations, and involved, at least partially, in agriculture. Results and conclusions A total of 120 botanical taxa were recorded. Ethnobotanical data included medicinal (40.4%), alimentary (46.5%), veterinary (4.6%), domestic and cosmetic (4.3%), magic and ritual (1.8%) and other uses (2.4%). Medicinal plants are used to treat a wide range of diseases, mainly disorders of digestive system, skin, and genital–urinary and respiratory traits. The key role played by undomesticated edible herbs, locally known as “erbette”, in traditional cooking recipes of RS was shown. These botanicals are rich in bioactive compounds, such as polyphenols, vitamins, complex sugars, essential fatty acids and fibers, and therefore might offer a valid protection against pathological conditions. Plant uses by RS people were compared with previous ethnobotanical literature, concerning the neighbouring areas of Liguria. Our results highlight the role of the traditional use of plants in the maintenance of health and the prevention of chronic and age-related diseases.

Crop changes from the XVI century to the present in a hill/mountain area of eastern Liguria (Italy)

BackgroundChronological information on the composition and structure of agrocenoses and detailed features of land cover referring to specific areas are uncommon in ethnobotanical studies, especially for periods before the XIX century. The aim of this study was to analyse the type of crop or the characteristics of soil cover from the XVI century to the present.MethodsThis diachronic analysis was accomplished through archival research on the inventories of the Parish of St. Mary and those of the Municipality of Pignone and from recent surveys conducted in an area of eastern Liguria (Italy).ResultsArchival data revealed that in study area the primary means of subsistence during the last five centuries, until the first half of the XX century, was chestnuts. In the XVIII and XIX centuries, crop diversification strongly increased in comparison with previous and subsequent periods. In more recent times, the abandonment of agricultural practices has favoured the re-colonisation of mixed woodland or cluster-pine woodland.ConclusionAncient documents in the ecclesiastic or municipal inventories can be a very useful tool for enhancing the knowledge of agricultural practice, as well as of subsistence methods favoured by local populations during a particular time and for reconstructing land use change over time.

FROM MAGMATIC TO METAMORPHIC DEFORMATIONS IN A JURASSIC OPHIOLITIC COMPLEX: THE BRACCO GABBROIC MASSIF, EASTERN LIGURIA (ITALY)

A new structural study with multiscale detailed analysis of the main elements of the fabric was performed on the Bracco ophiolitic massif (Eastern Liguria). The results are here presented with a reconstruction of the sequence of events which characterized the evolution of the gabbroic complex, starting form the first magmatic phases up to the late metamorphic ones, through a retrograde path which ended with the final exposure of the gabbro on the ocean floor. The field observations, supported by petrographic analyses, lead to outline for the Bracco Gabbroic Complex a deformative evolution which started in the early magmatic phases; the study of the metamorphic structures, following the intrusion and the syn-magmatic deformation of the gabbroic complex, allowed to identify three distinct metamorphic phases, whose petrographic features show that the associated deformations could actually represent a continuous evolution of the same tectonic phenomenon, which started under granulitic facies conditions, continued in amphibolitic facies and ended with deformations and recrystallizations in greenschist facies conditions.

Slope instability on rocky coast: a case study of Le Grazie landslides (eastern Liguria, northern Italy)

Abstract The stretch of rocky coast between Rapallo and Chiavari (Tigullio Gulf) is characterized by significant geomorphological instability phenomena, mainly contained between the shoreline and the Via Aurelia. Research was focused particularly on the geomorphological features and the states of activity of the landslides that are situated below the Santuario di N. S. delle Grazie. The dynamics can be partially attributed to natural causes, including the geological–tectonic layout, the geomechanical properties of the rock mass and wave undercutting, and partially to human activity related to the opening of limestone quarries and the construction of roadway, railway and communications networks. The recent evolution of the landslides, involving buildings, structures and infrastructure, requiring a variety of consolidation measures and work, has been observed. The latter were implemented following in-depth analysis of the subsoil geology and monitoring activity.

Cassagnaite, a new, V-bearing silicate mineral from the Cassagna mine, northern Apennines, Italy

Cassagnaite occurs at the Cassagna manganese mine (Eastern Liguria, Italy), filling fractures in braunite +quartz layered mineralizations together with piemontite. It occurs as very rare isolated prismatic to tabular {001} crystals, usually elongated along [100], and as entangled aggregates of a few crystals. Few aggregates consist of very small cassagnaite crystals (maximum size up to 0.05 mm) closely associated with much larger piemontite, quartz, and braunite crystals. The crystals are generally very small, with a maximum size up to 0.1 mm, golden brown in colour, transparent with vitreous lustre. The crystal structure, refined in the space group Cmcm with cell parameters a = 6.066(1) A, b = 8.908(1) A, c = 18.995(2) A and Z = 2, may be described as a layer stacking along [001] of a fundamental building block of composition [M1 2 (OH) 2 (SiO 4 ) 2 ] 4− that alternates with intersheets, randomly occurring in a ratio ideally 1:1, of type 1 [(Ca, Mn 2+ ) 2 SiO 2 ] 4+ and of type 2 (Ca, Mn 2+ ) 2 M2 2 (OH) 2 O 2 ] 4+ , where Fe 3+ and Mn 3+ populate 3/4 of the M1 site and Al the remaining 1/4, while V 3+ , Mg and Al occupy in nearly equal proportions the M2 site. The simplified formula, inferred from chemical analyses, structure refinement and crystal-chemical considerations, may be written as (Ca, Mn 2+ ) 4 (Fe 3+ , Mn 3+ , Al) 4 (OH) 4 (V 3+ , Mg, Al) 2 (O, OH) 4 (SiO 4 ) 2 (Si 3 O 10 ). From the composition of the “dominant” end-member of the complex solid-solution the end-member formula Ca 4 Fe 4 3+ (OH) 4 V 2 3+ O 2 (OH) 2 (SiO 4 ) 2 (Si 3 O 10 ) may be proposed for cassagnaite. So, cassagnaite may be classified as sorosilicate with insular and triple tetrahedral groups and belongs to the ardennite group in Dana’s classification.

Mineralogical and geochemical characterisation of open-air tailing and waste-rock dumps from the Libiola Fe-Cu sulphide mine (Eastern Liguria, Italy)

Active acid mine drainage (AMD) processes at the Libiola Fe-Cu sulphides mine are mainly triggered by water–rock interaction occurring within open-air tailing and waste-rock dumps. These processes are mainly controlled by exposure to weathering agents, the grain size of the dumped materials, and by the quantity of sulphides, the sulphide types, and their mode of occurrence. Due to these factors, several paragenetic stages of evolution have been recognised at different depths at different sites and within the same site. The dump samples were investigated with mineralogical (reflected- and transmitted-light optical microscopy, XRPD, and SEM-EDS) and geochemical (ICP-AES, Leco) techniques. The AMD evaluation of the tailing and waste-rock samples was performed by calculating the Maximum Potential Acidity, the Acid Neutralising Capacity, (and the Net Acid Producing Potential. The results allowed us to demonstrate that the open-air tailings had already superseded their AMD apex and are now practically inert material composed mainly of stable goethite ± lepidocrocite ± hematite assemblages. On the contrary, the sulphide-rich waste rocks still have a strong potential to produce long term AMD, causing the acidification of circulating waters and the release of several hazardous elements.

In vivo volatiles emission and essential oils from different organs and pollen of Cistus albidus from Caprione (Eastern Liguria, Italy)

AbstractThe composition of the essential oils obtained from the whole flowering tops and from isolated flowers and leaves of Cistus albidus L. (Cistaceae) has been investigated. The three essential oils were constituted mainly by sesquiterpene derivatives, but they showed quite different compositions. In the flowering tops and flowers the main constituents were α‐zingiberene, α‐cadinol and ar‐curcumene, while in the leaves the principal compounds were α‐cadinol, juniper camphor, germacrene D and spathulenol. Furthermore, the volatiles emitted in vivo by whole flowers, petals, sepals, pollen and leaves were investigated by means of SPME. Also in these analyses, sesquiterpenes were the main constituents but with a clear dominance of hydrocarbon derivatives. The whole flowers, petals, sepals and leaves of C. albidus showed a similar emission pattern of volatiles, whereas the pollen showed a very different profile. Copyright © 2006 John Wiley & Sons, Ltd.

Pollen, herds, jasper and copper mines: economic and environmental changes during the 4th and 3rd millennia BC in Liguria (NW Italy)

This paper reviews the interdisciplinary projects carried out during the last 25 years in eastern Liguria (NW Italy). These have brought together archaeologists, geographers, palaeobotanists and historians in a series of research exercises based upon many different types of evidence: archaeological excavation and survey, ecological analysis of existing landscapes, geoarchaeological, anthracological and palynological analyses. Taken together, the results of this research provide a rich source of material for developing an understanding of how humans in eastern Liguria have interacted with the landscape through time. The influence of human activity on the vegetation of Liguria, in the Late Neolithic, Copper Age (Chalcolithic) and Bronze Age, is part of a complex system of agricultural activity mainly involving transhumant pastoralism. Several peat sites and buried soils have supplied the palaeoecological data that indicate the considerable effect of this economic activity on the landscape: a reduction in fir woodland, a decrease in arboreal species and an increase in the diversity of light demanding herbaceous and fern taxa. The environmental and economic changes during the 4th and 3rd millennia BC in eastern Liguria are also testified to by the starting of quarrying and mining activities to obtain both red jasper and copper.

Genetic evolution of nanocrystalline Fe oxide and oxyhydroxide assemblages from the Libiola mine (eastern Liguria, Italy): structural and microstructural investigations

The Libiola Fe-Cu-sulphide mine, near Sestri Levante (eastern Liguria), represents one of the most extensively exploited sulphide deposits in Italy. In this area, active Acid Rock Drainage (ARD) processes are evident. The major resulting mineral phases are Fe oxides and oxyhydroxides, occurring in varicoloured crusts on the surface of waste rocks and in unconsolidated muds. In this study, the Fe assemblages of the waste rock were investigated by microchemical (SEM), structural (XRD), microstructural (TEM) and spectroscopic (DRS, IR, μ-Raman) techniques, in order to determine the phase composition, the textural relations among the minerals and their genetic evolution. They are characterized by intimate intergrowths of hematite and goethite with minor quartz and lepidocrocite; in some samples, the presence of very minor schwertmannite was detected. TEM and HR-TEM observations revealed that hematite is present within pseudo-elliptical bodies as pseudo-hexagonal to subrounded nanocrystalline lamellae (from 18.9 to 26.5 nm in diameter), whereas goethite occurs either as parallel intergrowths of acicular crystals (from 10 to 16.3 μm in length) or as sheaf-like assemblages. On the basis of the present data, the studied Fe oxide and oxyhydroxide assemblages are found to represent distinct spatial and temporal stages of a nano-scale evolution process.

Evidence of Marine Isotope Stage 5.5 highstand in Liguria (Italy) and its tectonic significance

The Quaternary shoreline displacements in Liguria are still poorly known. This paper completely revises and reinterprets the literature on this topic, taking into account only those markers that allow precise estimates of altitude and age of sea-level highstands. Among the sites showing geomorphological evidence of MIS 5.5 present in Liguria, three were considered reliable. In Eastern Liguria a beach deposit, with a terrace inner margin at 28 m a.s.l (Villa Monteverde), was dated by OSL. In Western Liguria, in a site close to the French border (Balzi Rossi), a notch present inside two caves indicating a sea-level altitude of 12 m is associated with a deposit containing a faunal assemblage with Strombus bubonius. This gastropod appeared in the Italian Seas only during the last interglacial highstand, and provides a unique marker of the MIS 5.5 horizon. Eastward, near Imperia, another site (Madonna dell’Arma) shows similar evidence, but in this case, the notch is not preserved because the cave is carved in a very soft Oligocene conglomerate. Late Quaternary tectonic movements along the different tracts of the Ligurian coast seem to have occurred apparently with different, although rather low, uplift rates. The connection between the Alpine and Apennine chains (Sestri-Voltaggio line) divides the Ligurian arch into two parts. The Alpine sector can be considered stable, whereas the Apennine relief displays in its central part an uplift rate of 0.16 mm/yr.

Late Miocene remagnetization within the internal sector of the Northern Apennines, Italy

Paleomagnetic and geologic evidence indicates that Upper Jurassic radiolarian cherts of both the Tuscan Cherts Formation (continental margin, Tuscan Units) and the Monte Alpe Cherts Formation (oceanic crust, Ligurian Units) were remagnetized during Miocene orogenesis of the Northern Apennines of Italy. Characteristic overprint magnetizations with reversed polarities have been found over a large area within the internal sector of the Northern Apennines, including eastern Liguria, Elba Island and the Thyrrenian margin, and west of the Middle Tuscan Ridge. The reversed-polarity overprint (average direction: D=177°, I=−52°, α 95=15°) was most likely acquired during Late Miocene uplift and denudation of the orogenic chain, and thermochemical remagnetization was a probable consequence of increased circulation of orogenic fluids. Similarly, mostly reversed-polarity directions of magnetization have been found by other workers in overlying post-orogenic Messinian sediments ( D=177°, I=−57°, α 95=3°), which show little counterclockwise (CCW) vertical-axis rotation with respect to stable Europe (−8±5°). The Monte Alpe Cherts sampled at sites in the external sector of the Northern Apennines, close to major tectonic features, have normal-polarity overprint directions with in situ W–SW declinations. Since the overlying post-orogenic Messinian sediments have not been substantially rotated about vertical axes, the evidence points to an earlier, pre-Late Miocene remagnetization in the external parts of the orogenic chain.

THE BARGONASCO - UPPER VAL GRAVEGLIA OPHIOLITIC SUCCESSION, NORTHERN APENNINES, ITALY

The Northern Apennines ophiolitic successions pertain to the Ligurian orogenic units, which were thrust onto the Adria continental margin (Tuscan and Umbrian Units) and show two different types of stratigraphic settings (Fig. 1) (Abbate et al., 1980): a- as “oceanic basement” of the Vara Supergroup, one of the higher units of the tectonic pile (“Internal Ligurides”); b- as olistoliths of variable sizes, accompanied by ophiolitic breccias, included in the Upper Cretaceous - Eocene terrigenous successions of the “External Ligurides” tectonic units. The Val Graveglia-Bargonasco area represented in the map, is located in eastern Liguria, on the northwesternmost side of the Northern Apennine, where most and more complete ophiolitic sequences of type a- crop out (the “Mt. Porcile Unit, Fig. 1). They consist of mantle peridotites (from clinopyroxene-poor lherzolites to harzburgites) and gabbros, which form the “oceanic basement”, metamorphosed and tectonically denudated before the volcano-sedimentary cover (ophiolitic breccias, basalts, cherts, carbonate and carbonate- shaly pelagites, and finally siliciclastic turbidites) was deposited. The tectonic scheme (Fig. 1, partially modified from the “schema tettonico” of the geologic map) shows that the Porcile Unit, object of our study, includes seven subunits separated by minor thrusts, i.e., from west to east, Mt. Domenico, M. Bianco, Rio Gromolo, Mt. Ciazze, M. Bocco, Rivo Orti, Mt. Tregin Subunits. The stratigraphic successions of all the Subunits pertain to the Vara Supergroup (see the stratigraphic Scheme on the geologic map). This short note summarises a more extensive one, about the geologic evolution of this same area, which will be published in the Atti Ticinensi di Scienze della Terra, Pavia, Italy, 2004. We decided to write this short summary to advertise the map of this key area for understanding the geology of the Northern Apennine ophiolites.

Prima segnalazione di un terrazzo costiero con deposito marino nella Liguria orientale (Italia)

Remnants of a loose coarse deposit were found on a rock terrace 28 m above the present day sea level, along the coast of Eastern Liguria. A general geomorphological analysis of the site was carried out. The deposit sedimentological characteristics were detailed and a morphometric analysis of the coarse fraction was carried out. This enabled us to infer the marine genesis of the deposit; it is the first time that a Quaternary marine deposit is found along the coast of Eastern Liguria. Details regarding the nature of the deep weathering processes (in particular oxidation and decarbonatation) that affected it were collected by means of thin section. The age of an old sea level can be inferred, due to the absence of absolute dating, only relating it to similar surfaces present throughout the coastline of the region and linking them to the sea level curves obtained from oxygen isotope records. On the basis of the collected data we propose the chronological attribution of the studied terrace to theδ18O stage 11, considering that the area might have been affected by tectonic uplift.

STRUCTURAL FABRIC OF THE ANTOLA UNIT (RIVIERA DI LEVANTE, ITALY) AND IMPLICATIONS FOR ITS ALPINE VERSUS APENNINE ORIGIN

A new tectonic interpretation of the Antola Unit is presented for the eastern Liguria (from Genova to Chiavari). Five tectonic episodes are recognizable, all developed in the brittle-ductile field. The first three tectonic episodes took place before the deposition of the Portofino Conglomerate (Early Oligocene) whereas the last two episodes are not quite defined. The first episode (F1) is characterized by rare folds with NW/SW vergence; the second episode (F2) is related to folds with SE vergence; the third episode (F3) is associated with sub vertical conjugate shear bands; the last two episodes are characterized by low angle shear planes (F4) with a top to NE/NW component of shear while the last episode (F5) is related to the transected cleavage folds with subvertical axial planes. The first three tectonic phases identified in the Antola Unit should be ascribed to the Alpine orogenesis; this interpretation agrees with that of Marroni and Pandolfi (1996) and of Ellero (1999; 2000) for the surrounding areas.

Alteration of braunite ores from Eastern Liguria (Italy) during syntectonic veining processes: mineralogy and fluid inclusions

Alteration of braunite ores from Eastern Liguria (Italy) during syntectonic veining processes: mineralogy and fluid inclusions

A new species of Festuca L. (Poaceae) from Liguria (Italy)

Summary F. veneris sp. nov., a local endemism of the rocky coasts of Portovenere and of Island of Palmaria (eastern Liguria, Italy) is described.

Pollen deposition in country villages of Eastern Liguria (Northern Italy)

Recent pollen rain in 14 country villages of Ligurian hinterland was examined, in the framework of pollen deposition studies based upon moss polsters analysis, now in progress. The above mentioned localities are prevailingly situated in the Trebbia, Aveto and Vara valleys, within 300 and 1000 m a.s.l. For each locality a moss sample was examined (two for Torriglia: north and south) consisting of several sub-samples from various zones of the built-up area. All the samples have proved rich in pollen and provided spectra in accordance with qualitative and quantitative features of the urbanized areas vegetation and the spontaneous one of the neighbourhood. Sticking to general considerations, an attempt was made to compare the present results with those of the city area of Genova, previously obtained with the same methods.

Pollen stratigraphy of two Holocene peat sites in the Ligurian Apennines, northern Italy

This paper presents the results of recent pollen-stratigraphical investigations of Holocene peat sites in eastern Liguria, northern Italy. Relative pollen data from two of the sites studied are presented together with pollen concentration data and four radiocarbon dates. The study area lies within the northern Apennines, a region from which few detailed late Quaternary palaeoenvironmental records have been published and from which no radiocarbon-dated pollen profiles have previously been reported. Peat accumulation in the Ligurian Apennines typically began during the period 4000 to 5000 B.P., a lack of early Holocene sediments probably having been due to widespread climatic conditions inimical to peat development. During the later middle Holocene montane forests were dominated by Abies but from approximately 2000 B.P. fir disappeared from the pollen records. Subsequently beech woodlands were predominant, a situation which remains to the present day. The problems of interpretation of this event in the pollen-stratigraphical data are examined.