NW Italy Research Articles

Grading Habitats for Ticks by Mapping a Suitability Index based on Remotely Sensed Data and Meta® population dataset in Aosta Valley, NW Italy.

Ticks represent a reservoir of zoonotic pathogens, and their numbers are increasing largely in wildlife. This work is aimed at producing maps of suitable habitats for ticks in Aosta Valley, Italy based on multitemporal EO data and veterinary datasets (tick species and distribution in wild hosts). EO data were processed in Google Earth Engine considering the following inputs: A) Growing Degree Ticks (GDT), B) NDVI from MOD09GA, C) NDVI entropy, D) distance from water bodies, E) topography, F) rainfalls from CHIRPS as monthly composites along the 2020, 2021 and 2022 years. Ticks were collected from hunted, injured, and found-dead wild animals ( Sus scrofa, Capreolus capreolus, Rupicapra rupicapra, Cervus elaphus); they were labeled at species level using taxonomic keys. Between September 2020 and December 2022, a total of 90 ticks were collected from 89 wild animals. Ixodes ricinus was the most prevalent tick species, followed by Dermacentor marginatusand Dermacentor spp. Molecular analyses demonstrated the presence of Anaplasma spp., B. burgdorferi sensu lato and Rickettsia spp. pathogens in infected ticks. To assess human population potential exposure to tick Meta® population dataset was used. In conclusion this study shows the potentialities of Remote sensing improving the technological transfer to the veterinarian sector.

Effects of urbanization on river morphology in a Mediterranean coastal city (Genova, Italy)

From the geomorphological point of view, urbanization changes fluvial systems more drastically than any other single human activity. Its impact on rivers is of interest as it results in serious issues concerning geomorphic instability, ecosystem service reduction, and geo-hydrological risk increase. The present study provides a quantitative and qualitative assessment of landscape changes driven by urbanization, which occurred from the mid-19th century to the present day along the lower reaches of the Bisagno and Polcevera rivers and their tributaries in the Mediterranean coastal city of Genova (NW Italy). The bankfull channel morphological adjustments, the minor hydrographic network disappearance, the land use and land cover changes, and the current physical accessibility of river margins were investigated. This work is based on collection and review of historical data, photograph interpretation, GIS analysis, and field surveys. Urbanization essentially occurred between the mid-19th century and the late 1930s. The bankfull channel of the Bisagno and Polcevera rivers experienced large narrowing associated with widespread establishment of channelization structures. The minor hydrographic network essentially disappeared underground. After the 1930s, further minor anthropogenic interventions were implemented to accommodate urban expansion and consolidate channelization works; however, the overall geomorphological setting remained unchanged. The geomorphological evolution of the Bisagno and Polcevera rivers followed three different phases associated with the urban expansion process. Nowadays, the study area is completely urbanized, the fluvial stems flowing through the valley floor are totally disconnected from their adjacent areas, the main rivers show a relevant geomorphological stability induced by anthropogenic pressures, and the accessibility of river margins for people is rather limited. The outcomes from this study represent an essential knowledge base for technicians and policymakers to plan urban development and inform effective and sustainable management measures. Moreover, they provide insights into the medium- and short-term morphological evolution of urban rivers.

How to use efficiently airborne criteria pollutants and radon-222 in source apportionment: A self-organizing maps approach

Pollutant source apportionment represents one of the fundamental activities in environmental science. Several efficient chemometric tools are available to the scope, mostly based on multivariate techniques and usually applied to aerosol chemical speciation data. In the present work, an alternative source profiling method is proposed, based on the self-organizing maps (SOM) algorithm. Moreover, the dataset used includes typical criteria pollutants and physical parameters related to airborne particulate matter widely used as a complement of aerosol source apportionment and largely available at a higher time resolution than bulk aerosol samplings, allowing the information on the dynamic behavior of the local airshed to be extended. In this work, data was collected at a coastal location in NW Italy, between January and July 2012. Hourly concentrations of typical gaseous pollutants (SO2, NO, NO2, benzene, toluene, (m-p)-xylene, o-xylene), black-carbon and particle number concentrations by an optical particle sizer (OPS) were collected. The dataset was integrated with radon-222 activity concentration and meteorological parameters to enrich and refine the information obtained by SOM computation as well as to improve the air pollution source localization. Despite the lower specificity of criteria pollutants, the approach developed was capable of revealing distinct pollution sources such as the urban background traffic, the coal-fired power plant active at the time of the study, and the harbor, in agreement with previous PM-based source apportionment studies carried out locally, while enlightening peculiar dynamical conditions detectable at the sub-daily time scale. The application of the SOM algorithm, with the integration of meteorological parameters and atmospheric radon, proved to be very efficient in unveiling the air pollution sources.

Environmental factors affecting the distribution of Spongillidae (Porifera) in an artificial channel (in north-western Italy)

The hydrographic network of the upper Po Valley (NW Italy) is characterized by the presence of numerous hydroelectric plants, often powered by artificial channels. These man-made water courses, which range from a few hundred meters to several kilometers in length, are used to convey water from the rivers to the electricity production plant. Power canals are usually characterized by concrete banks and bottoms, a geometric profile, and the absence of riparian vegetation so that they host peculiar invertebrate communities, often extremely well adapted to life in a completely artificial habitat. Sponges are an often little considered component of the freshwater macroinvertebrate fauna, whose functions and role within communities can be of considerable interest. These sessile, filter-feeding organisms can colonize artificial channels, but little is known about the local environmental characteristics that influence their distribution. In this study, we investigated the distribution of a freshwater sponge family Spongillidae, in a 4.5 km long artificial channel in Rocca Grimalda (Alessandria, NW Italy). A total of 863 specimens were localized and measured, and selected environmental characteristics were recorded. Results suggested that the distribution of sponges depends mainly on the lighting rather than the type of substrate or other local factors, so that this taxon is well-suited to colonizing artificial environments with good water quality conditions.

The Impact of Catastrophic Floods on Macroinvertebrate Communities in Low-Order Streams: A Study from the Apennines (Northwest Italy)

Floods are normal components of many river regimes and, as such, they exert a significant influence at the ecosystem level. In recent decades, however, climate change has increased the frequency and intensity of floods, with serious consequences for lotic biota, particularly benthic macroinvertebrates, due to their limited mobility and sensitivity to disturbance. The impact of floods varies according to different biological parameters including the characteristics of the macrobenthic communities (taxonomic composition, morphology, behaviour, and life history traits) on one hand and various nonbiological parameters such as flood intensity, artificialisation of the river bed, the presence of dams, and many other factors on the other. Understanding these dynamics is pivotal to improve the effective management and conservation of aquatic ecosystems in the context of current climate change. The aim of this short communication is to evaluate the impact of a catastrophic flood on the macroinvertebrate community of a low-order Appennine stream (NW Italy). This will provide data regarding the varying impacts on different taxa and the recovery pattern of this significant component of the ecosystem.

Distribution of fish species in the upper Po River Basin (NW Italy): a synthesis of 30 years of data

Freshwater fish is the most diverse group of vertebrates but, unfortunately, also one of the most threatened. While some well-known, charismatic species have been subject to important conservation efforts, many others have long been neglected. This paper aims to analyse the distribution over time of seven freshwater fish species and one lamprey in the upper Po River basin (NW Italy), an important biodiversity hotspot. Six of them are native species listed in Annex II of the Habitats Directive (Lampetra zanandreai, Protochondrostoma genei, Chondrostoma soetta, Telestes muticellus, Sabanejewia larvata, and Cottus gobio), while the other two are key invasive species (Silurus glanis and Misgurnus anguillicaudatus). Data from four regional fish population monitoring campaigns carried out between 1988 and 2019 were analysed. For each species and monitoring campaign, an average Representativeness Index, measuring abundance and population structure, and an Occurrence Frequency were calculated, and then assessed for changes over the time. Of the studied species, P. genei declined the most in the last 30 years, while C. soetta and S. larvata are in a very critical situation, with very few remaining populations. T. muticellus, C. gobio and L. zanandreai seem to have declined only slightly, but their vulnerability should not be underestimated. The two invasive species, on the other hand, show a substantial increase in occurrence as well as range. While some drivers for the decline in the native species vary according to their ecological and biological characteristics, others are more general and linked to the overall degradation of the river environments: habitat alterations, loss of connectivity, excessive water abstraction, pollution, and the presence of invasive alien species. The effects of climate change, such as the rise of inland water temperatures and the alteration of hydrological cycles, must also be taken into account. Diverse and far-reaching conservation efforts are needed to improve the fish habitat and thus also protect the unique biodiversity of this region.

Deep Electrical Resistivity Tomography for Detecting Gravitational Morpho-Structures in the Becca France Area (Aosta Valley, NW Italy)

Deep-seated gravitational slope deformations (DSGSDs) consist of gravity-induced, large-scale, gradual rock mass movements. In the Aosta Valley region (Valle d’Aosta NW Italy), DSGDs affect wide valley slopes and produce several interconnected morpho-structures that involve bedrock and Quaternary cover. Some DSGSD effects are not visible at the surface because of subglacial abrasion or burial by sediments and, therefore, are difficult to map with standard geomorphological surveys. This is the case for the Pointe Leysser DSGSD in the Aosta Valley, which is heavily influenced by the historical movements of the Verrogne-Clusellaz Glacier and its tributaries. We conducted a new geological investigation, integrated with deep electrical resistivity tomography geophysical surveys (ERTs). The ERT results were initially compared with geological/geomorphological evidence at the surface to define the correlation between the values and spatial distributions of electrical resistivity and the sediments, rocks, or morpho-structures. The resistivity values at various depths were subsequently analysed, interpreted, and discussed in conjunction with geological hypotheses. The geological and geophysical survey revealed three wide buried glacial valleys filled with glacial sediments and mapped the locations of gravitational morpho-structures at depth. These new data allowed us to draw a relationship between glacialism and gravitational evolution, distinguishing between pre-singlacial movements and postglacial movements.

The environmental and agronomic benefits and trade-offs linked with the adoption alternate wetting and drying in temperate rice paddies

ContextAlternating wetting and drying (AWD) is an irrigation practice, alternative to continuous flooding, to improve the agro-environmental sustainability of rice cultivation. Benefits include reduction in water consumption, methane (CH4) emissions and arsenic (As) concentrations in grain. However, drainage periods during AWD can negatively affect nitrogen (N) use efficiency by the crop and grain yields, while increasing nitrous oxide (N2O) emissions and cadmium (Cd) contents in grain. ObjectiveThe objective of this study was to provide a holistic evaluation of AWD adoption in temperate rice cropping systems, including associated trade-offs. We hypothesized that the adoption of AWD in water seeded rice paddies can reduce the global warming potential (GWP) without affecting plant N uptake or introducing yield gaps, and also maintain a high quality of rice grain by limiting the uptake of metal(loid)s present in the soil, thereby resulting in an overall positive agro-environmental performance. MethodsIn a two-year field experiment in NW Italy two alternative irrigation practices involving water seeding followed by AWD management of different severity (AWDsafe and AWDstrong) were evaluated relative to the conventional water seeding and continuous flooding (WFL), comparing three different rice varieties. Yields and yield components, plant N uptake, apparent N recovery (ANR), metal(loid) concentrations in grain, and CH4 and N2O emissions were evaluated. ResultsAWDsafe and AWDstrong maintained or increased yields compared to WFL depending on varieties, despite an increase in sterility. There were no consistent differences in N uptake and ANR. Both AWDsafe and AWDstrong significantly reduce As concentration in grain, but significantly increase Cd and nickel (Ni). AWDsafe and AWDstrong reduced CH4 emissions by 45–55 % and 40–73 %, respectively, compared toWFL, while no increase in N2O emissions was observed. This resulted in a reduction in the GWP of 46 and 54 % with AWDsafe and AWDstrong, respectively. Conclusions and ImplicationsAWD was shown to be effective for mitigating GHG emissions from temperate rice cropping systems while maintaining high yield performance comparable or higher than WFL. AWD may represent a viable alternative to continuous flooding to improve agro-environmental sustainability of temperate rice cropping systems, but the trade-off between decreasing As and increasing Cd and Ni contents in the grain may represent an important concern for food safety with the adoption of this alternative water management practice.

Stealth Metasomatism in Granulites from Ivrea (NW Italy): Hydration of the (Variscan) Lower Crust by Melt Flow

Stealth Metasomatism in Granulites from Ivrea (NW Italy): Hydration of the (Variscan) Lower Crust by Melt Flow

Assessment of a geomorphological-based design for coastal protection: The case of a wave-cut platform on the Bogliasco coast (Liguria Region, NW Italy)

Coastal erosion processes and the associated risks pose a significant challenge for coastal urban settlement administrations. Coastal managers are often seeking new approaches and solutions for coastal protection. Introducing protective structures such as breakwaters and groins often poses problems for management, e.g. modification of the natural panorama, changes within the local coastal dynamics and associated implications with regard to coastal hazards and risks. This paper describes a geomorphological-based approach to coastal structure design, taking as its study case the Bogliasco coast in the region of Liguria, near the eastern border of the municipality of Genova (Northwest Italy). Bogliasco is a stretch of rocky coast exposed to the most intense storms of the Liguria Sea and where the urban settlement reaches the edge of the cliff. To prevent cliff collapse and coastal flooding (and mitigate the associated risks), this study proposes an approach based on the structural recovery of an ancient wave-cut platform currently consumed by erosion. The recovered structure dissipates incoming waves, helping to mitigate both the erosive phenomena at the foot of the cliff and the risk of coastal flooding. The performance of the coastal protection project was evaluated by comparing the results of the XBeach model simulations for ante-operam and post-operam scenarios. The results indicate that the adopted solution contributes to a reduction of wave impact on the coast and the mitigation of flood hazards and risks. A geomorphological-based approach is therefore seen as a winning approach from both an engineering and management viewpoint.

A Study on the Factors Controlling the Kinematics of a Reactivated and Slow-Moving Landslide in the Eastern Liguria Region (NW Italy) through the Integration of Automatic Geotechnical Sensors

This paper deals with the investigation of factors influencing the movement patterns of a reactivated slow-moving landslide situated in the eastern Liguria region (NW Italy) through the analysis of extensive ground-based hydrological and geotechnical monitoring data. Subsurface horizontal displacement and pore water pressure data were acquired simultaneously by means of automatic sensors positioned at pre-existing and localized failure zones. The joint examination of field measurements enabled us to explore the connections between rain, pore water pressure, and displacements. The results of continuous displacement monitoring showed that the landslide kinematics involved phases of extremely slow movements alternated with periods of relative inactivity. Both stages occurred prevalently at seasonal scale displaying similar durations. The slow-motion phases took place at relatively constant pore water pressure and were ascribed to mechanisms of viscous shear displacements along failure surfaces. Inactive phases entailed no significant deformations, mostly corresponding to prolonged dry periods. The two motion patterns were interrupted by episodic sharp deformations triggered by delayed (preparation periods from 4 to 11 days) rainfall-induced pore water pressure peaks, which were ascribed to sliding mechanisms taking place through rigid-plastic frictional behaviour. During these deformation events, hysteresis relationships between pore water pressure and displacement were found, revealing far more complex hydro-mechanical behaviour.

The Age of Granulite-Facies Metamorphism in the Ivrea–Verbano Zone (NW Italy) Determined Through In Situ U–Pb Dating of Garnet

Abstract Rates of melt production, extraction and crystallization, as well as scales of melt transfer and interaction with their residuum change continuously in migmatite and granulite, affecting the behavior of monazite and zircon as time capsules. Therefore, accessory mineral chronometers may be ambiguous and incomplete in providing an overview of the temperature–time evolution of high-grade metamorphic rocks. In this study, we applied the novel technique of in situ U–Pb dating of garnet to the archetypal lower continental crust of the Ivrea–Verbano Zone (IVZ), NW Italy. In the IVZ, the temporal relationship between granulite-facies metamorphism and mafic underplating has long been debated, because of the interplay between tectonic, magmatic, metamorphic and metasomatic processes over a period of more than a hundred million years. Garnet from mafic and pelitic granulites yielded U–Pb ages between 287.4 ± 4.9 Ma and 280.1 ± 12.4 Ma, overlapping within uncertainty the time proposed for the emplacement of the Mafic Complex (286–282 Ma). These results indicate that the thermal climax in granulitic rocks was caused by mafic underplating and concomitant asthenospheric upwelling, rather than being inherited from the post-Variscan Carboniferous evolution. Providing robust dating of garnet with as low as 4 ng/g U, this study demonstrates the strength of garnet petrochronology in resolving complex tectono-metamorphic histories of high-grade terranes. It also represents a further step forward towards establishing garnet as part of the in situ U–Pb geochronology repertoire.

Evaluation of an innovative, open-source and quantitative approach for the kinematic analysis of rock slopes based on UAV based Digital Outcrop Model: A case study from a railway tunnel portal (Finale Ligure, Italy)

This paper presents a novel, cost-effective method for a rapid and quantitative characterization of discontinuities in fractured rock cliffs using Unmanned Aerial Vehicle-derived Digital Outcrop Models (DOMs). The proposed workflow combines manual extraction of discontinuity data from the DOM with a kinematic analysis using an automated algorithm (ROKA), which upgrades and renews the traditional Markland's test. The case study, a designed railway tunnel portal in NW Italy (Finale Ligure) demonstrates the advantages and limitations of this approach compared to current methods. Manual mapping is compared with (semi-)automatic extraction of discontinuity data from the DOM and validated with field-based scan lines. The results show that in complex geological settings, manual mapping provides more statistically robust and geologically reliable measurements of discontinuity orientation, validated by the user's expertise. Traditional stereographic approaches in kinematic analysis are limited in characterizing spatially variable slopes and discontinuity networks, providing only generic estimations of unstable slope surfaces and discontinuity intersections. This limitation is overcome by new algorithms that incorporate 3D spatial relationships of both the discontinuity network and the rock slope, resulting in a more accurate and site-specific kinematic characterization of the rock cliff, emphasized by 3D visualizations of the critical planes and potential rock failure volumes. The new approach significantly impacts the time, effort, and cost of the engineering projects, allowing to quantitatively define the potential unstable areas with a fast analysis. The Authors stress the importance of integrating digital workflows with comprehensive field-based characterizations of the local litho-stratigraphic and structural setting to effectively utilize large datasets and partially automated procedures.

Impact of wastewater treatment and drought in an Alpine region: a multidisciplinary case study

In the context of global climate change, drought occurrence in streams of alpine origin is a recent phenomenon, whose impact is still poorly investigated. In this study, we adopted a three-disciplinary approach to investigate the response of an Alpine river (NW Italy) to severe drought conditions occurred in the year 2022. We hypothesised that the considerable loss in the water flow could exacerbate wastewater treatment plant (WWTP) discharge effects, lowering dilution capacity of the stream system and then increasing chemical/microbial pollution and altering benthic community characteristics. To assess river response to drought conditions of the considered year, the concentration of the main chemical variables, faecal indicator bacteria, pathogen presence and structural/functional organisation of benthic macroinvertebrates and diatom communities were measured monthly in the reaches located upstream and downstream of a WWTP (January–December 2022). Main environmental variables, such as flow velocity, water depth, and flow regime, were also considered. A multivariate analysis approach was then applied to emphasise correlations between selected variables and flow regime.Comparing upstream and downstream sections over the considered year, a common behaviour of chemical/microbiological parameters was observed, with generally higher concentrations of nutrients and bacterial indicators downstream of the local WWTP. Moreover, a positive correlation between water scarcity and nutrients/bacterial concentrations was revealed. The macroinvertebrate communities responded accordingly, both in terms of density and biological metric shift.Interestingly, differences between the two sections were strictly associated with hydrological conditions, with higher dissimilarities found in low-flow conditions. As the magnitude and duration of drought events are projected to increase in the years to come in different parts of Europe, this work can serve as a first building block and as a hint for future studies aimed at improving our knowledge about the consequences of these events that is pivotal for planning effective management strategies.

The Database of the Ornamental Stones of Piemonte (NW Italy) Hosted on a WebGIS Service

The Database of the Ornamental Stones of Piemonte (NW Italy) Hosted on a WebGIS Service

Three new species for the odonatofauna of Piedmont (NW Italy)

Between 2020 and 2023, three new species of Odonates were recorded in Piedmont (NW Italy). Lestes barbarus was observed at an artificial wetland in the Turin Plain in 2021. Even though at least one individual was fresh, we cannot conclude that the species developed at the site. Subsequent visits did not permit to confirm the species. Coenagrion hastulatum was discovered at a peat bog in the NW Alps (Lac Falin, Valle di Viù) in 2023 and here reproduction was confirmed. This population is the fifth to be recorded for the central and western Italian Alps. Trithemis annulata was first recorded in Piedmont in July 2020, and subsequently, the observations of the species in the region rapidly increased, with a total of 66 records relative to 29 sites up to the end of 2023. These are distributed in most of the low-altitude areas of the region. The species was reported mostly in late summer, with only one site where the early spring records suggest successful overwintering. However, this needs further confirmation. The odonate list of Piedmont now accounts for 70 species, representing 73.6% of the taxa reported for Italy, and this makes Piedmont, along with Lombardy, the most odonate-rich region of Italy.

Exploring the Correlation between Geoheritage and Geodiversity through Comprehensive Mapping: A Study within the Sesia Val Grande UNESCO Global Geopark (NW Italy)

While geoheritage and geodiversity have been well defined in the literature, the multiplicity of definitions given to these two concepts makes it difficult to establish an unambiguous relationship between them. Basing on semantic-ontological studies, this study aims to reduce this ambiguity within the concepts by investigating the relationship between the geodiversity richness and the presence of geoheritage, and discussing whether the areas with the greatest geodiversity are the ones with the most relevant geoheritage, thus questioning the potential use of the geodiversity index map. Upon a strong theoretical framework, a quantitative geodiversity index map was created for the Alagna Valsesia municipality, within the Sesia Val Grande UNESCO Global Geopark (Italian Western Alps). Then, 25 geosites were identified and mapped in the same area. Notably, the exploration into the correlation between geodiversity and geoheritage on the field shows that in our study area there is no spatial correlation between the geodiversity class and the number of geosites, proving that some geosites may occur in areas of low geodiversity and the greatest geodiversity are not the ones with the most relevant geoheritage. Moreover, all the non-parametric regression models tested are not significant, indicating that there is no predictable relationship between geodiversity and geoheritage in Alagna Valsesia (NW Alps). For that reason, our work highlights that although the quantitative geodiversity map can have an important role for geoconservation and within biodiversity studies, it could not be a strong tool for geosites recognition and tourism promotion, while for this purpose should be better use a qualitative geodiversity map. Finally, the potential use of the geodiversity map depends on the purpose of the study and the approach used to produce it. For a comprehensive geoconservation and geoheritage promotion strategy, the two approaches (qualitative and quantitative) may be complementary.

Resilient coral reef ecosystems: The case study of turbid-mesophotic coral buildups during the Late Oligocene Warming Event (Tertiary Piedmont Basin, NW Italy)

Nowadays, but also in the geological record, coral communities living in marginal conditions (i.e. low light, high turbidity, extreme temperatures, high nutrients and sediment input) are quite common and there is evidence that some of these reefs, often associated with mesophotic environments, may be more resilient to the current global warming trend, thus serving as possible ecological refugia.As an attempt to understand the response and resilience to past warming events of marine calcifying organisms, such as zooxanthellate corals of marginal reefs, herein we reconstruct the palaeoenvironment of an Oligocene mixed siliciclastic‑carbonate system in the Tertiary Piedmont Basin (NW Italy), where a suite of coral assemblages formed small buildups at the edge of a coarse-grained delta system. Geochronological dating by strontium isotope stratigraphy places the coral buildups in the middle Chattian, thus within the Late Oligocene Warming Event (LOWE): a crucial climatic event for coral reefs as characterised by substantial warming coincident with declining atmospheric CO2.The depositional model that we propose is ascribed to a fan-delta system, deposited within a narrow valley cutting through the metamorphic basement, where small and laterally discontinuous coral buildups grow-up in the prodelta setting, thus suggesting a mesophotic environment. In this context, the coral buildups appear to have been intermittently deactivated or smothered by fine-grained terrigenous input during flood phases or shifts in distributary channels until their final suffocation by fluvial sediments input.Within the coral buildups, the four distinguished coral facies (branching Stylophora floatstone, Acropora-Stylophora floatstone/rudstone, Goniopora/Caulastraea pillarstone, and mixed-coral domestone) are characterised in general by sediment-resistant corals and by specific taphonomic features.These coral facies shifted in time and space during the LOWE, highlighting the noteworthy adaptability and resilience of Oligocene corals to a complex interplay of environmental stressors such as turbidity, hydrodynamic energy, sediment and nutrient supply within a mesophotic setting.

Continent-derived metasediments (Cimes Blanches and Frilihorn) within the ophiolites around Zermatt: relations with the Mischabel backfold and Mont Fort nappe (Pennine Alps)

The region surrounding Zermatt (SW Switzerland and NW Italy) displays some classic examples of imbrications between continental and oceanic units. In particular, the studied units, called Cimes Blanches and Frilihorn or Faisceau Vermiculaire, consist of a set of thin bands of continent-derived metasediments intercalated at different levels within the ocean-derived units. These bands are locally reduced to only one meter thick but can be traced for several tens to more than one hundred kilometers across the Pennine Alps. The mechanisms leading to such imbrications are a long-standing and still-debated question. Based on detailed mapping and structural analysis of key areas, we present new data on the structure and stratigraphy of the Faisceau Vermiculaire in the area surrounding Zermatt, with particular focus on the Täschalpen sector, where the Faisceau Vermiculaire is locally in contact with basement units. Our observations allow: (i) to confirm the presence of widespread breccias of probable Jurassic age in the Faisceau Vermiculaire; (ii) to interpret the contacts between the Faisceau Vermiculaire and the overlying non-ophiolitic Schistes Lustrés (Série Rousse) as stratigraphic; (iii) to show that the stratigraphy of the Faisceau Vermiculaire and associated Série Rousse contrasts strongly with the cover of the Siviez-Mischabel nappe and that these sequences originate from different paleogeographic domains (Prepiemont basin and Briançonnais platform respectively); (iv) to interpret as stratigraphic the contact of the Faisceau Vermiculaire and the Série Rousse with the basement forming the Alphubel anticline; the local unconformity is interpreted as the result of the activity of synsedimentary Jurassic normal paleofaults; (v) to highlight the trace of a major Jurassic normal fault, that should have marked an abrupt thinning of the paleomargin; it corresponds now to the contact between the Faisceau Vermiculaire (and associated Série Rousse) and the Siviez-Mischabel basement in the hinge of the Mischabel backfold. We propose a new tectonic scheme for the structure of the Faisceau Vermiculaire and adjacent units involving an early northward folding of the Faisceau Vermiculaire with the Série Rousse and the ophiolitic Schistes Lustrés of the Tsaté nappe, followed by major backfolding responsible for the southward emplacement of these units above the HP Zermatt-Saas and Monte Rosa nappes. Our study at regional scale shows that the group formed by the Alphubel basement, the Faisceau Vermiculaire and the Série Rousse share a tectonic position and stratigraphic sequences identical to those of the Mont Fort nappe, which outcrops on the other side of the Dent Blanche klippe. It leads to the proposition that this group constitutes the eastern extension of the Mont Fort nappe.

Unraveling ecological signals related to the MECO onset through planktic and benthic foraminiferal records along a mixed carbonate-siliciclastic shallow-water succession

The shallow-water Capo Mortola succession (Liguria, NW Italy) yields diverse assemblages of smaller benthic and planktic foraminifera, larger benthic foraminifera (LBF), and calcareous nannofossils. With the aim of improving the understanding of the Middle Eocene Climatic Optimum (MECO) impact on the shallow-water marine biotic communities due to global warming, we provide biostratigraphic and stable isotope data to achieve a reliable stratigraphic constraint of the MECO. The correlation of the stable isotope oxygen data with datasets of similar age from other regions suggests that only the onset of the MECO interval is recorded in the Capo Mortola section. Quantitative analyses of smaller benthic foraminiferal assemblages indicate that the shallow-water setting of Capo Mortola was not particularly affected by the onset of the MECO perturbance because no variation in nutrient supply or oxygen level were detected. A different scenario is recorded by the LBF genera Operculina and Discocyclina, which increased in abundance across the MECO onset, probably due to a rise in temperature and adapting to the increase in nutrient supply. In the upper water column, the variations in calcareous plankton communities appear to be controlled by both the MECO warming and a moderate increase in eutrophic conditions related to the enhanced hydrological cycle. Nutrients, mostly consumed in the upper water column, reached the seafloor in a limited amount, as benthic foraminifera record a meso-oligotrophic environment across the studied MECO interval.