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Questa tesi tratta della creazione di modelli 3D strutturali su larga scala (x1) e su scala locale (x2) di regioni delle Alpi Pennine, per cui introduco workflow di modellazione 3D che combinano dati strutturali di terreno (sia originali che già pubblicati) con algoritmi di modellazione implicita. L'approccio di modellazione implicito rappresenta l'architettura tettonica costruendo un’analogia tra la distanza relativa tra strutture geologiche e un campo scalare volumetrico. In questo campo, le strutture geologiche sono rappresentate da superfici di equipotenziali, e la loro geometria è vincolata da osservazioni geologiche di terreno che influenzano sia valore che l'orientamento del campo scalare. In particolare, in questa tesi utilizzo l'algoritmo Discrete Smooth Interpolator. Le aree di studio sono situate nelle Alpi nord-occidentali, tra il Monte Bianco e il Monte Rosa, e non sono mai state oggetto di uno studio di modellazione 3D di questa portata. Nella regione sono esposti il dominio Austroalpino, il Piemontese, il Pennidico e il sistema Elvetico-Ultraelvetico. Questa sequenza tettonica è rappresentata nel primo modello 3D presentato in questa tesi, che si estende per circa 1.500 km2 lungo il confine tra Italia e Svizzera. Il workflow di modellazione per questo modello prevede la creazione di interpretazioni strutturali in sezioni verticali, necessarie a ottenere un risultato che rispetti principi di realismo geologico. Il risultato è un modello deterministico che cattura la conoscenza dell'architettura tettonica a scala regionale, rappresentando strutture quali zone di taglio, pieghe ripiegate, isoclinali e/o coricate, e il reticolo di faglie. Successivamente, la tesi si focalizza su due regioni di dimensioni inferiori (estensioni inferiori ai 30 km2), quali l'area del Lago di Cignana e la dorsale Tournalin-Roisetta, locate all'interno dei confini del modello regionale. Con l'obiettivo di minimizzare l’input soggettivo interpretativo, i workflow di modella, The overarching theme presented this thesis is the generation of large (x1) and local-scale (x2) 3D structural models of regions of the Pennine Alps, for which I introduce modelling workflows that combine high-resolution new and legacy structural datasets derived from fieldwork with implicit modelling algorithms. The implicit approach builds the tectonic architecture as an analogy between the relative distance among geological structures and a volumetric scalar field, within which geological structures are represented as isovalue surfaces. In particular, in this thesis I employ the Discrete Smooth Interpolator algorithm. The study areas, situated in the northwestern Alps between Mont Blanc and Monte Rosa, lacked prior comprehensive three-dimensional representations. This region exhibits the Austroalpine-Penninic collisional wedge and the Helvetic-Ultrahelvetic sequence of thrust sheets. This tectonic sequence is represented in the first, regional-scale 3D model presented in this thesis, spanning approximately 1,500 km2 along the Italian-Swiss boundary. The modelling workflow for the creation of this model incorporates structural interpretations on vertical cross-sections to propagate geological knowledge to the subsurface, ensuring the geological realism of the final outcome, resulting in a deterministic model that provides a comprehensive summary of the tectonic architecture and captures the state of the knowledge about the region. Geological structures represented by the model include hierarchical shear zones, isoclinal and/or recumbent folds, and networks of faults. Successively, I redirect my attention to two more localised regions (extensions less than 30km2) encompassed within the boundaries of the regional model, the Lago di Cignana area and the Tournalin-Roisetta ridge. With the objective of reducing subjectivity and uncertainty of the final outcomes, I employ techniques that rely on the abundance of the structural database and leverage constraints provided

Durante gli eventi eruttivi, il magma si propaga verso la superficie attraverso dicchi verticali. Tuttavia, nella maggior parte dei casi, questi dicchi si arrestano nella crosta, senza provocare un'eruzione. La messa in posto di dicchi nella parte più superficiale della crosta provoca una concentrazione di sforzi di trazione e taglio nella roccia incassante, che possono portare a deformazioni fragili sulla superficie topografica, con la formazione di fratture estensionali e faglie normali, spesso creando un graben. Negli ultimi decenni sono stati utilizzati modelli analitici, analoghi e numerici per analizzare la relazione tra l’intrusione di magma e la deformazione superficiale indotta dai dicchi; la maggior parte di questi modelli, però, utilizza uno semispazio elastico, omogeneo e isotropo, senza tenere conto delle eterogeneità della crosta. Per superare questa limitazione ed evitare errori nella ricostruzione della geometria del dicco, quindi, è necessario prendere in considerazione dati realistici raccolti sul campo. Per questo motivo, in questo progetto, ho integrato dati strutturali realistici con la modellazione numerica. Le aree di studio sono situate sull'Etna (Italia), lungo le fessure eruttive del 1928 e del 1971, e nel sud-ovest dell'Islanda, lungo la fessura eruttiva “Younger Stampar”. Questi casi di studio sono stati tutti interessati dalla messa in posto di dicchi a basse profondità. Sull'Etna, ciò ha portato ad una deformazione fragile della superficie, che oggi è ancora visibile in pianta e, per il caso di studio del 1971, anche in sezione. Lo scopo principale è quello di indagare i parametri che i) promuovono o inibiscono la deformazione fragile indotta dai dicchi in superficie, ii) controllano la geometria delle faglie del graben indotte dai dicchi e iii) favoriscono l'arresto dei dicchi a basse profondità. Per raccogliere nuovi dati strutturali, ho integrato il classico lavoro sul campo con analisi su modelli 2D e 3D ad alta risoluzione, During eruptive events, magma propagates vertically towards the surface through magma-filled fractures, referred to as dikes. However, in most cases dikes arrest in the crust, not leading to an eruption. In shallow settings, dike emplacement causes a concentration of tensile and shear stresses in the host rock, which can lead to brittle deformation at the topographic surface, with the formation of tension fractures and normal faults, often creating a graben. In the last decades, analytical, analogue and numerical models have been designed to analyze the relation between magma emplacement and dike-induced surface deformation, but mostly with an elastic half-space, homogeneous and isotropic, without taking into account the layering of the crust. Realistic field data should be considered to overcome this limitation, to avoid errors in the reconstruction of dike geometry. For this reason, in this project, I integrated realistic structural data with numerical modeling. Study areas are located on Mt. Etna (Italy), along the 1928 and 1971 eruptive fissures, and in SW Iceland, along the Younger Stampar eruptive fissure. These case studies were all affected by shallow dike emplacement. On Mt. Etna, this led to brittle surface deformation, which is nowadays still visible in plan view and, for the 1971 case study, also in section view. The main aim is to investigate the parameters that i) promote or inhibit dike-induced brittle deformation at the surface, ii) control the geometry of dike-induced graben faults, and iii) favor dike arrest at shallow depths. To collect new structural data, I integrated classical fieldwork with remote sensing analyses, thanks to high-resolution 2D and 3D models derived from drone-collected images and historical aerial photographs through Structure from Motion (SfM) techniques. All these data were then used as inputs for Finite Element Method (FEM) numerical modeling using the software COMSOL Multiphysics®, running sensitivity analyses to understan

Active fold-and-thrust belts create new landslide-prone slopes during tectonic deformation propagation. However, studies on landslide distribution in newly formed fold-and-thrust belts are limited. In this study, we present a new inventory of landslides in the Kura fold-and-thrust belt, a tectonically active, but relatively low-altitude southern margin of the Greater Caucasus. The area has been tectonically framed in the last ~2–3 Ma and is represented by folds and thrusts deforming Miocene to Quaternary sediments. Through satellite imagery analysis, we mapped nearly 1600 landslides, with a quarter currently active. While landslides cover <1 % of the area, they tend to cluster at higher elevations and in regions with relatively high local relief. Landslides predominantly occur in tectonically uplifted areas, affecting the highest and steepest parts of growing anticlines and the steep slopes of incising valleys intersecting active thrust faults. Based on observed landslide distribution in folds at different stages of development, we propose a conceptual model for the temporal evolution of landslide patterns in weak sediment-based fold-and-thrust belts: 1) In the initial stages, slow-moving slope deformations affect incipient thrust fronts. With the flanks of the growing anticline lacking sufficient steepness, landslides tend to concentrate in deep valleys intersecting the uplifting hanging walls. 2) With ongoing thrust uplift, growing and steepening anticlines become more prone to planar sliding when dip slopes exceed friction angle, and valley development creates additional dip slopes, resulting in widespread landslides. 3) In the final stage, erosional decay reduces topographic relief, leading to badland formation with gully erosion and decreased landslide occurrence.

Late Cretaceous metamorphic events are known in Crete and the Cyclades from klippen above the External Hellenides. This work extends their occurrence to the North Aegean area within the tectonic units of the Internal Hellenides. New 40Ar/39Ar white mica ages from garnet-bearing micaschists of the Upper Metamorphic Unit of Skyros Island, cropping out in the Skyrian Olympus Mountain, document a Late Cretaceous tectono-metamorphic evolution. Several mica generations have been distinguished using electron probe microanalyses and were dated using the 40Ar/39Ar method: a relict mica older than 96 Ma, followed by a foliation-forming mica of about 88–84 Ma and alteration phases ≤ 68 Ma were recognized. This Cretaceous tectono-metamorphic evolution falls between the closure of the internal Axios/Vardar oceanic basin in the Late Jurassic–Early Cretaceous, and the closure of the external Pindos–Cyclades oceanic basin in the Early Cenozoic. The position of the Upper Metamorphic Unit of Skyros was probably within the evolving Hellenic volcanic/magmatic arc during the continuous subduction of the African plate beneath the European plate. The present tectonic position of the units bearing the Late Cretaceous metamorphic event is the result of the Cenozoic tectonic emplacement onto the more external units across the Hellenides from the Pelagonian to the Pindos–Cyclades domain.

Geodynamic models implying subduction of continental crust either consider this process happening during collision, when the continental margin of the lower plate attempts subduction, or in pre-collisional stages, when tectonic erosion of the upper plate or subduction of continental extensional allochthons drag continental crust in the subduction channel. In the Zagros orogen (W Iran), high-pressure rocks are known only from the Sanandaj-Sirjan Zone, NE of the Main Zagros Thrust. Here, eclogites of the North Shahrekord Metamorphic Complex suggest subduction of continental crust slices derived from the upper plate (Central Iran) during the onset of the Neo-Tethys subduction along the southern margin of Iran. Eclogites record a clockwise pressure-temperature-time path, with pre-eclogitic epidote-amphibolites-facies phase assemblages preserved in garnet cores, a high-pressure stage, and a subsequent retrogression at amphibolite-facies conditions. By means of forward thermodynamic modelling and 40Ar/39Ar geochronology, the peak metamorphism has been constrained at 1.9-2.1 GPa and 550-600 °C, in the 191-194 Ma time span. The following retrogression during exhumation lasted at least until 144 Ma. Our data suggest that the onset of the Neo-Tethys subduction traces back prior to 190 Ma, involving together with the Neo-Tethys oceanic lithosphere also slices of the upper plate continental crust scraped off by means of tectonic erosion processes.

Dykes and sills occupy Mode I (extension), Mode II (shear), or hybrid mode fractures and most of the time transport and store magma from deep reservoirs to the surface. Subject to their successful propagation, they feed volcanic eruptions. Yet, dykes and sills can also stall and become arrested as a result of the crust’s heterogeneous and anisotropic characteristics. Dykes can become deflected at mechanical discontinuities to form sills, and vice versa. Although several studies have examined dyke propagation in heterogeneous and anisotropic crustal segments before, the conditions under which dykes propagate in glacial-volcanotectonic regimes remain unclear. Here, we coupled field observations with 2D FEM numerical modelling to explore the mechanical conditions that encourage (or not) dyke-sill transitions in volcanotectonic or glacial settings. We used as a field example the Stardalur cone sheet-laccolith system, which lies on the Esja peninsula, close to the western rift zone, NW of the southern part of the Icelandic rift. The laccolith is composed of several vertical dykes that transition into sills and form a unique stacked sill ‘flower’ structure. Here, we investigate whether the Stardalur laccolith was formed under the influence of stresses caused by glacial retreat due to thickness variations (0–1 km) in addition to regional and local tectonic stresses (1–3 MPa extension or compression) and varied magma overpressure (1–30 MPa), as well as the influence of the mechanical properties of the lava/hyaloclastite contact. Our results show that the observed field structure in non-glacial regimes was formed as a result of either the mechanical (Young’s modulus) contrast of the lava/hyaloclastite contact or a compressional regime due to pre-existing dykes or faulting. In the glacial domain, the extensional stress field below the ice cap encouraged the formation of the laccolith as the glacier became thinner (subject to a lower vertical load). In all cases, the local str

Contractional deformation structures at the front of transpressional orogens display complex three-dimensional geometries deviating from the interpretative templates commonly applied in thrust belts. Accordingly, detailed constraints on deformation patterns and associated paleofluid circulation are desirable, especially for fracture geometry and permeability predictive purposes. The Pag anticline, which is located in the Dinaric fold and thrust belt, provides an appropriate field site for studying fold- and fault-related deformation structures in a transpressive setting. We performed a multiscale structural analysis together with petrographic and stable isotope characterization of the deformation-related calcite cements. Structural mapping suggests that the Pag anticline is a detachment fold developed mainly by buckling, since large-scale thrust faults are absent. Fold tightening in a transpressive setting produced a complex deformational structure including two sets of N-S right-lateral and E-W left-lateral late-stage strike-slip fault sets trending oblique to the NW-SE fold axis. The pre-folding deformation pattern includes incipient normal faults likely related to the forebulge stage, veins and stylolites coherent with NE-SW layer parallel shortening contraction in a strike-slip regime, and metric to decametric scale conjugate thrusts coherent with layer parallel shortening in a compressive regime. Buckle folding preceded propagation of a series of accommodation structures during fold tightening. Petrographic and isotopic data indicate meteoric alteration of the Cretaceous platform carbonates in the prefolding stage, likely due to forebulge subaerial exposure. Layer parallel shortening and early syn-folding veins involved formational fluids resulting from mixed marine and meteoric fluids during folding at shallow burial conditions. Eventually, meteoric fluid infiltrated again along strike-slip faults, acting as cross-formational conduits in the postfolding stage.

Understanding the mechanical conditions for dike arrest and associated surface deformation or, alternatively, dike propagation to the surface to supply magma to an eruption, is of fundamental importance for volcanology in general and for volcanic hazards in particular. Here we present the results of a study of an outcrop located in the Reykjanes Peninsula, SW Iceland, where one dike became arrested only 5 m below the surface of an active volcanic system, without inducing any brittle deformation at the surface. In the same outcrop, at a distance of 30 m, a feeder dike is exposed. Both dikes are associated with the Younger Stampar eruption (1210–1240 CE). We reconstructed a high-resolution 3D model, through drone surveys and Structure from Motion (SfM) techniques, on which we collected detailed structural data combined with field surveys. These data, integrated with petrographic and geochemical analyses, became inputs to Finite Element Method (FEM) numerical models, made using the COMSOL Multiphysics® software. Our results indicate that compression exerted by the intrusion of the feeder dike (inferred to have been emplaced first) can explain the arrest of the second dike and the absence of induced brittle deformation even if the dike tip is only 5 m below the surface. Furthermore, the contrasting mechanical properties of the layers that constitute the outcrop, with alternating stiff lavas and compliant tuffs, raise (concentrate) the compressive stresses in the lava flows ahead of the second dike, thereby encouraging its arrest. Both the dikes are basaltic, but the earlier emplaced feeder dike is crystal poor and slightly more evolved than the later emplaced arrested dike. The results throw a new light on the conditions for dike arrest and (the lack of) dike-induced brittle deformation at very shallow depths in active rift zones, with important implications for volcanic-hazard assessments.

The study of selected logs from the Central-Eastern Iran Microplate (CEIM; area of Arusan) and Sanandaj–Sirjan Zone (SSZ; areas of Esfahan east and Tiran) constrains timing and evolution of the Cretaceous successions, resting unconformably on older sediments or non-conformably on the metamorphic basement. The Cretaceous marine transgression occurred almost synchronously on a levelled topography, documenting a previous deep erosion. Above a basal siliciclastic unit, rudist- and orbitolinid-rich lower Aptian limestone (“Orbitolina Limestone”, Shak Kuh Formation, Taft Formation) were deposited. Later, the stratigraphic evolution of the three studied areas differentiates, documenting changes in the depositional environments, reflecting different subsidence rates. In the Tiran area, marls and cherty limestones covering shallow-water limestones record a deepening trend. A differentiation of depositional environment is observed at Arusan, where conglomerates to the west pass to basinal sandstone and marls to the east. Here, a Coniacian-Campanian reprise of the carbonate production (with skeletal limestones rich in rudists, ostreids, and abundant orbitoidids) is covered by cherty marls. In the Esfahan north area, glauconitic hardground marls covered by chert record important deepening during the early Cenomanian, followed by the reprise of shallow-water carbonate production (middle Cenomanian). The synchronous deposition of Aptian carbonate successions on large parts of the CEIM, SSZ and North-Iranian domains suggests a rapid regional transgression controlled by a sea-level rise. Stratigraphic differentiation occurring in late Aptian–Cenomanian times, recording the onset of tectonic events differently affecting the aforementioned domains, likely related to the opening of oceanic seaways in the CEIM and the SSZ.

The central Southern Alps (N Italy) preserve stratigraphic evidence of the Early Jurassic rifting related to the opening of the Alpine Tethys, despite its later involvement in the Alpine orogeny. Here, the extensional tectonics produced rapid facies and thickness changes of the Liassic succession, interpreted as syn-rift deposits, documenting a horst and graben architecture postdating a Rhaetian shallow-water homogeneous succession. Despite the identification of several extensional syn-depositional faults bordering structural highs, no geochronological constraints were until now available to confirm the Early Jurassic age of these faults. In this work geochronological constraints obtained by LA-ICP-MS U-Pb dating on syn-tectonic carbonate veins associated with extensional faults are presented for the first time. Field work (Seriana Valley, N Italy) led to the identification of N-S trending syn-depositional faults, the Amora Fault System, that borders a deep half-graben filled with Lower Jurassic cherty limestones (Moltrasio Limestone). The syn-depositional activity of these faults is documented by stratigraphic evidence, different thickness of the hangingwall and footwall successions, and facies association (such as abundant slump overfolds and mass flow deposits). In the study area, clear cross-cutting relationships between structures and middle Eocene magmatic bodies document three main tectonic events: 1) the E-W oriented extensional phase; 2) a N-S oriented extensional phase characterized by the emplacement of andesitic dikes; 3) the N-S oriented Alpine compression. The relative age constraints permitted to focus on the E-W extensional phase, related to the opening of the Lombardian basin. Carbonate syn-tectonic veins and slickenfibers were sampled in the Norian to Lower Jurassic successions, both in the footwall and in the hangingwall of the Amora Fault System. O-C stable-isotopes analyses and U-Pb dating were performed on 21 samples, based on previous microstr

The Vinschgau Shear Zone (VSZ) is one of the largest and most significant shear zones developed under plastic conditions within the Austroalpine domain, juxtaposing the Ötztal and the Texel units to the Campo, Scharl and Sesvenna units during the building of the Eo-Alpine Orogen. The VSZ dominates the structural setting of a large portion of the central Austroalpine Late Cretaceous thrust stack. In order to fully assess the evolution of the VSZ, a multi-faceted approach based on detailed multiscale structural and petrochronological analyses has been carried out across representative transects of the shear zone in the Vinschgau Valley. The research has been performed with a view to characterizing kinematics, P-T conditions and timing of motion of the VSZ. Our fieldwork-based analyses suggest that the dip angle of mylonitic foliation increases from west to east with an E-W-trending stretching lineation which dips alternatively to the west and to the east, due to later folding related to the Cenozoic crustal shortening. The dominant top-to-W shear sense of the mylonites recognized in the field and confirmed by microstructural analyses led to exhumation of the upper Austroalpine nappes in the hanging wall of the shear zone; the Texel unit with Late Cretaceous eclogites and the Schneeberg and Ötztal units were all affected by Eo-Alpine amphibolite-facies metamorphism. Chemical and microstructural analyses suggest deformation temperatures of ca. 350-400C during shearing. Timing of deformation along the VSZ has been constrained for the first time through 40Ar/39Ar dating of syn-shearing micas, which reveal a Late Cretaceous age of the VSZ mylonites with ages ranging between 80 and 97Ma. A systematic younging age of deformation occurs towards the central part of the shear zone in the studied transects. Vorticity analysis shows a clear decrease in the simple shear component correlated to the younging of mica ages towards the core of the shear zone. This evolution is consis

Le Ande Meridionali e Patagoniche costituiscono una barriera orografica ai venti occidentali del Pacifico, condizionando così il clima e la distribuzione di acqua e ghiaccio nel Sud America meridionale. L'orogenesi andina si verifica almeno dal Cretaceo, guidata dalla subduzione di litosfera oceanica sotto il continente sudamericano. Le loro altezze elevate a latitudini extra-tropicali condizionano l’erosione fluvio-glaciali che condiziona, almeno in parte, il loro sollevamento, l'esumazione delle rocce e la localizzazione di deformazioni e vulcanismo. Le Ande Patagoniche meridionali (a sud di 46°S) sono caratterizzate da cinture di pieghe e sovrascorrimenti dal tardo Cretaceo al Miocene e da complessi magmatici attualmente situati sopra una finestra astenosferica. Nella zona orogenica interna affiorano rocce metavulcaniche sedimentarie del bacino di Rocas Verdes (RVB) del tardo Giurassico-inizio Cretaceo. La modellizazione termodinamica metamorfica, la geocronologia U-Pb su zircone e 40Ar/39Ar su fengiti nelle rocce del RVB ci permettono di determinare l'inizio dell'orogenesi andina tra ca. 83 e 70 Ma attraverso il loro sottoscorrimento tettonico fino a ~23 km. Questa fase è stata seguita dalla subsidenza dell'avampaese nel tardo Cretaceo e da compressione, plutonismo e subduzione della dorsale oceanica nel Miocene. La modellizazione inversa dei dati (U-Th-Sm)/He su apatite e zircone provenienti dalle rocce dei massicci di Torres del Paine (TdP, 51 °S) e del Fitz Roy (FzR, 49 °S) permette di quantificare la suddivisione tra le forzanti tettoniche e climatiche sul sollevamento regionale e sull’esumazione delle rocce. Un episodio di esumazione rapida nel FzR tra ca. 10,5 e 8,5 Ma è interpretato come forzato dalla risalita del mantello durante la subduzione della dorsale a quella latitudine. Un episodio condiviso di esumazione rapida a ca. 6,5 Ma in entrambi i massicci registra l'inizio delle glaciazioni patagoniche, seguito da una quiescenza dell'esumazione fino a, The Southern and Patagonian Andes constitute an orographic barrier to Pacific westerly winds, thus conditioning the climate and water/ice distribution in southern South America. Andean orogeny occurs since at least the Cretaceous, driven by oceanic subduction beneath the South American continent. Their high elevations in extra tropical latitudes condition the occurrence of fluvio-glacial erosion that control, at least partially, the surface uplift, the rock exhumation, and the localization of deformation and volcanism. The southern Patagonian Andes (south of 46 °S) are characterised by Late Cretaceous to Miocene fold-and-thrust belts and magmatic complexes currently located above an asthenospheric window. Meta-volcano-sedimentary rocks from the Late Jurassic-Early Cretaceous Rocas Verdes Basin (RVB) outcrop in the internal orogenic zone. Metamorphic thermodynamic modelling, zircon U-Pb, and and phengite 40Ar/39Ar geochronology in RVB rocks allow us to determine the onset of the Andean orogeny between ~83 and 70 Ma through their tectonic underthrusting down to ~23 km. This phase was followed by Late Cretaceous foreland subsidence, and Miocene compression, plutonism, and ridge subduction. We also perform inverse modelling of apatite and zircon (U-Th-Sm)/He data from the rocks of the Torres del Paine (TdP, 51 °S) and the Fitz Roy (FzR, 49 °S) massifs. The newly produced data allows us to quantify the partitioning between the tectonic and climate forcing on the regional uplift and rock exhumation. An episode of fast exhumation in the FzR between 10.5 and 8.5 Ma is interpreted as forced by mantle upwelling during ridge subduction at that latitude. A shared episode of fast exhumation at ~6.5 Ma in both massifs records the onset of Patagonian glaciations, followed by a quiescence of exhumation up to 2 Ma. The last acceleration of the exhumation from 2 Ma to present-day is likely linked to a shift in the glacial-interglacial cyclicity. In the Southern Andes Volanic Zone (33

The most common way of magma transfer towards the surface is through dyking. Dykes can generate stresses at their tips and the surrounding host rock, initiating surficial deformation, seismic activity, and graben formation. Although scientists can study active deformation and seismicity via volcano monitoring, the conditions under which dykes induce grabens during their emplacement in the shallow crust are still enigmatic. Here, we explore through FEM numerical modelling the conditions that could have been associated with dyke-induced graben formation during the 1928 fissure eruption on Mt. Etna (Italy). We use stratigraphic data of the shallow host rock successions along the western and eastern sections of the fissure that became the basis for several suites of numerical models and sensitivity tests. The layers had dissimilar mechanical properties, which allowed us to investigate the studied processes more realistically. We investigated the boundary conditions using a dyke overpressure range of 1–10 MPa and a local extensional stress field of 0.5–2 MPa. We studied the effect of field-related geometrical parameters by employing a layer thickness range of 0.1–55 m and a variable layer sequence at the existing stratigraphy. We also tested how more compliant pyroclastics, such as scoria, (if present) could have affected the accumulation of stresses around the dyke. Also, we explored how inclined sheets and vertical dykes can generate grabens at the surface. We propose that the mechanical heterogeneity of the flank succession and the local extensional stress field can largely control both the dyke path and dyke-induced graben formation regardless of the tested dyke overpressure values. Similarly, soft materials in the stratigraphy can greatly suppress the shear stresses in the vicinity of a propagating dyke, encouraging narrow grabens at the surface if only the fracturing condition is satisfied, while inclined sheets tend to form semigrabens, respectively. Finally, we p

Durante il Permiano Inferiore, l’evoluzione post-Varisica dell’attuale regione Alpina è stata caratterizzata da una importante estensione crostale combinata con intensa attività magmatica, che ha favorito lo sviluppo di bacini estensionali intra-continentali con deposizione di sedimenti vulcanoclastici (e.g. Bacino Orobico). Nel settore centrale delle Alpi Meridionali, l’apertura di questi bacini era controllata da complessi sistemi di faglia, attivi contemporaneamente con l’intrusione di plutoni e l’attività vulcanica in superficie. Il seguente progetto di dottorato si focalizza sullo studio di queste caratteristiche, con l’intento di approfondire i processi geologici attivi durante il Permiano. Diverse faglie di età Permiana sono state indagate nel Bacino Orobico, con particolare enfasi sul riconoscimento dei loro tratti originali, poiché esse sono eccezionalmente sfuggite alla deformazione Alpina. Nel passato, l’architettura dei bacini Permiani era stata descritta con strutture a horst-graben, formatesi in risposta ad una tettonica transtensiva controllata da una zona di taglio che ha portato alla trasformazione da Pangea B a Pangea A. Tuttavia, studi più recenti hanno indicato un diverso setting di faglie che hanno controllato l’apertura dei bacini Permiani: si tratta di una combinazione di faglie normali a basso e alto angolo. Le faglie normali a basso angolo identificate lungo il Bacino Orobico rappresentano il miglior luogo in cui osservare l’interazione tra attività tettonica e magmatismo, poiché i loro nuclei di faglia sono caratterizzati da cataclasiti sigillate da livelli di tormaliniti. Queste ultime testimoniano la circolazione di fluidi arricchiti in boro e incanalati lungo importanti zone di faglia correlate all’apertura del Bacino Orobico. Simili brecce a tormalina affiorano anche in Val Trompia (BS): molti autori hanno suggerito che le tormaliniti delle Alpi Orobie, quelle della Val Trompia unitamente alla mineralizzazione di uranio del dist, During the Early Permian, the post-Variscan evolution of the present-day Alpine region was characterized by crustal extension combined with strong magmatic activity at different crustal levels, which finally led to the development of intracontinental extensional basins filled with volcanoclastic sediments (e. g. the Orobic Basin, N Italy). In the central Southern Alps (cSA), the opening of these basins was controlled by complex fault system that were active at the same time of plutons intrusion and volcanic activity at the surface. Relationships among magmatism, tectonics and hydrothermal activity related to the formation of ore deposits in the Early Permian so far have been only briefly addressed. This Ph.D. research project focuses on the investigations of the above described features, trying to consider the geological processes active in the Early Permian in an integrated scenario. Several Early Permian faults of the Orobic Basin have been investigated with special emphasis on the recognition of their original features, as they have exceptionally escaped most of the Alpine deformation. In the past, the architecture of Permian basins was described as horst-and-graben structures, formed in response to wrench tectonics developed during the activity of a megashear zone that led to the Pangea B to Pangea A transformation after the collapse of the Variscan orogen. However, thanks recent studies, a different fault architecture has been suggested to had controlled the opening of the Permian basins: a combination of Low-Angle Normal faults and High-Angle Normal Faults. The identified LANFs of the Orobic Basin represent the best site to study the interplay among tectonics and magmatism, as they are characterized by cataclastic bands sealed with cm to dm thick layers of dark, aphanitic tourmalinites. These latter are proof of fluids circulation channelled along higher permeability fault zones related to opening of the Orobic Basin. Such tourmaline breccias also crop out in

Low-Angle Normal Faults (LANFs) represent in the central Southern Alps area (N Italy) the main structures along which the Variscan basement is in contact with the Upper CarboniferousPermian volcanic-sedimentary succession. Tourmalinites frequently occur along LANFs, usually replacing former cataclasites. The mineralogy and chemical composition of tourmalinites point to a metasomatic origin. LANFs, together with high-angle faults, controlled the opening of the Permian Orobic Basin and likely acted as a preferred pathway for hydrothermal fluids that triggered the Boron-metasomatism. Along the Aga-Vedello LANF, tourmalinites appear to have formed after the cessation of fault activity, as no brittle post-metasomatism deformation overprint has been observed. These relationships suggest that the circulation of B-rich fluids occurred after the opening of the Orobic Basin that is broadly constrained to the Early Permian. At the same time, ca. 285–270 Ma, a strong magmatic activity affected all the Southern Alps, ranging in composition from mafic to acidic rocks and from intrusions at deep crustal levels to effusive volcanic products. The Early Permian magmatism was likely the source of the late-stage hydrothermal fluids that formed the tourmalinites. The same fluids could also have played a significant role in the formation of the Uranium ore deposit of the Novazza-Vedello mining district, as the ore bodies in the Vedello valley are concentrated along the basement-cover contact.

The physical processes that operate within, and beneath, a volcano control the frequency, duration, location and size of volcanic eruptions. Volcanotectonics focuses on such processes, combining techniques, data, and ideas from structural geology, tectonics, volcano deformation, physical volcanology, seismology, petrology, rock and fracture mechanics and classical physics. A central aim of volcanotectonics is to provide sufficient understanding of the internal processes in volcanoes so that, when combined with monitoring data, reliable forecasting of eruptions, vertical (caldera) and lateral (landslide) collapses and related events becomes possible. To gain such an understanding requires knowledge of the material properties of the magma and the crustal rocks, as well as the associated stress fields, and their evolution. The local stress field depends on the properties of the layers that constitute the volcano and, in particular, the geometric development of its shallow magma chamber. During this decade an increasing use of data from InSAR, pixel offset and structure-from-motion, as well as dense, portable seismic networks will provide further details on the mechanisms of volcanic unrest, magma-chamber rupture, the propagation of magma-filled fractures (dikes, inclined sheets and sills) and lateral and vertical collapse. Additionally, more use will be made of accurate quantitative data from fossil and active volcanoes, combined with realistic numerical, analytical and machine-learning studies, so as to provide reliable models on volcano behaviour and eruption forecasting.

Innovations in virtual reality (VR) technology have led to exciting possibilities in teaching earth sciences, allowing students to experience complex geological sites that, due to cost and logistical reasons, they would not normally be able to experience. The need for high quality online digital learning resources and blended learning was brought to the forefront during the SARS-CoV-2 pandemic, as courses with a traditional physical field work component were forced to move online and provide alternatives to students. While it is unlikely that virtual field trips (VFT) would be accepted by students as a replacement of real-world fieldwork moving out of the pandemic, research shows promise that using IVR experiences can lead to enhanced learning outcomes in geosciences, warranting its inclusion on the curricula. This paper presents the outputs of a project to improve student learning in complex geological environments using VR. Here we outline a workflow that was developed to collect high resolution imagery using remote sensing to create digital outcrop models (DOM) of complex geological sites. Using this framework, this paper will then explore the use of VR for an investigation of the Husavik Triple Junction, a complex structural site in northern Iceland, explaining how the drone data was converted to a 3D DOM and demonstrating how VR can be used to simulate real world field mapping. Finally, we describe how these IVR activities have been integrated into taught modules at postgraduate level and discuss how the use of IVR experiences can complement existing geoscience curriculum design.

Collecting quantitative and extensive datasets in the field is fundamental in structural geology, stratigraphy, and sedimentology, rock mechanics, and in other fields of the Earth and planetary sciences. Digital Outcrop Models (DOMs) provide a 3D framework for collecting these large datasets and can be obtained from laser scanning or photogrammetric surveys, carried out either with an avionic platform (airplane, helicopter, drone) or with terrestrial methods. In this chapter we review best-practice methods for collecting DOMs, focusing particularly on terrestrial and drone photogrammetric surveys and on critical issues that determine their efficiency, reliability, and accuracy. Then we compare the two main formats for DOMs: point clouds (PC-DOMs) and textured surfaces (TS-DOMs). Finally, we outline typical goals and workflows for the geological interpretation of DOMs on PC- and TS-DOMs, either from laser scanning or photogrammetric surveys.

Collecting quantitative data to support geological analysis and modelling is nowadays a fundamental requirement in all geology disciplines, including structural geology, stratigraphy, and geomorphology, on the Earth and on planetary bodies of the Solar System. In many cases the answer to this need is a Digital Outcrop Model (DOM), a Digital Elevation Model (DEM), or a Shape Model (SM): this can be a digital representation of an outcrop or topographic surface, or of a whole small body (asteroid or comet nucleus) for an SM, generally combined with imagery, that can be quantitatively visualized and studied in 3D, with the goal of obtaining quantitative measurements. 3D datasets and models for geological purposes include different complementary products: DEMs, DOMs, SMs, and subsurface models. The main differences among these different products are: (i) their nature, since DEMs, DOMs, and SMs represent relief surfaces showing outcropping geological structures that are completely accessible to characterization (up to some precision/resolution), while subsurface models reproduce inaccessible subsurface geological structures with some unavoidable level of uncertainty (hence they are models); and (ii) their topology/dimensionality, as DEMs are actually 2.5D surfaces, generally covering large areas, DOMs are truly 3D surfaces, including multivalued reliefs (e.g. complex or overhanging reliefs, cliffs, caves, etc.), but are generally limited to smaller-scale outcrops, and SMs are closed surfaces covering a whole small body, where subsurface models are essentially volumetric. In this volume we collect various examples of methods and techniques used to collect, analyze, and model 3D datasets, based on one or more supports (DEM, DOM, SM, subsurface model), and on different software tools, remote sensing, and modelling techniques. Reading the chapters authored by experts in different fields, it will become apparent that (i) the fundamental techniques allowing the production of DE

The exhumation of the Lepontine Dome in the Central Alps was mainly driven by extensional shear zones at its borders. The Simplon Shear Zone (SSZ), formed as a consequence of east-west lateral extrusion perpendicular to north-south convergence between Adria and Europa plates, has been the leading structure in the exhumation of the western sector of the Lepontine Dome where the deepest rocks of Central Alps are nowadays exposed. We present here a multidisciplinary study of the SSZ combining fieldwork, microstructural analyses, vorticity estimates, quartz c-axis fabric analysis, quartz paleopiezometry and 40Ar/39Ar geochronology. The SSZ evolved from epidote-amphibolite to greenschist facies and then brittle conditions during shearing. A decrease of simple shear component from 88% to 37% towards the top of the shear zone is observed, with mylonites displaying ages within the 12-8 Ma time interval. Differential stress (59–78 MPa) and strain rate (10−11-10−12 s−1) estimates are in agreement with values obtained for crustal-scale low-angle normal faults developed at medium to shallow crustal levels. Our multiscale and multidisciplinary approach points out that the SSZ experienced a complex evolution, with shear strain heterogeneously distributed across the shear zone in the frame of a decrease of the simple shear component and increase of the differential flow stress toward the top of the shear zone.

Despite that many field studies on joint attribute statistics are available in the literature, there is still an ongoing debate on the most effective statistical treatment to properly describe the distribution of a fundamental parameter like joint spacing. This may also relate to the objective difficulty of collecting very large datasets from single linear scanlines directly in the field, because of limited exposures. To overcome such a limitation, we selected a spectacular outcrop of the Miocene Marnoso-Arenacea Formation turbidite sandstones located near the Coniale village, in the Northern Apennines (Italy), where a vertical cliff provides a 100% continuous outcrop about 90 m high and 280 m long, with well-accessible exposures at its base, along the Santerno River. This setting allows combining data acquisition on a photogrammetric DOM (digital outcrop model) covering a representative sector of the outcrop, with ground truthing by direct measurements in the field. More than 2000 joints were identified in 9 linear scanlines traced in the DOM along mechanical layers with different thickness. Comparison with field data indicates that both joint orientation and spacing data from the DOM are very reliable. The scanlines include between 549 and 37 joints, depending on layer thickness, allowing to perform robust statistical analysis. The Kolmogorov-Smirnov (K–S), Cramer-von Mises (CvM) and Anderson-Darling (A-D) nonparametric tests were used to identify the probability density function(s) that best fit spacing data among exponential, Gamma, log-normal and normal distributions. The Gamma distribution turned out as the most probable in most cases. In some specific sectors along all scanlines, joint density is significantly greater than the average for the presence of joint clusters. In some cases, joint clusters are vertically aligned with those in underlying and/or overlying scanlines, thus resulting in thoroughgoing joint corridors. Comparison of spacing statistics insi

Understanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.

The Middle–Upper Triassic Aghdarband Basin, NE Iran, consists of a strongly deformed marine and non-marine stratigraphic succession, deposited along the southern margin of Asia in a highly complex tectonic context related to a back-arc setting. The youngest deformed units of the Aghdarband area consist of a rather monotonous sequence of brown-colored shales, with intercalations of siltstones and fine-grained sandstones forming the Miankuhi Formation. The shale-dominated Miankuhi Formation rests on an unconformity surface, separating it from the underlying Sina Formation. A multidisciplinary study based on sedimentological, palynological, and paleobotanical data permits to reconstruct the depositional environments, sedimentary evolution, and paleoclimate conditions of the upper Sina and the lowermost Miankuhi formations. The palynological association of the lowermost part of the Miankuhi Formation yielded sporomorphs of the latest early Carnian to early late Carnian age. Qualitative and quantitative analyses document a shift from xerophytic associations in the upper Ladinian (upper Sina Formation) to hygrophytic assemblages in the Carnian (lower Miankuhi Formation). This increase in hygrophytic elements is also observed in coeval Tethyan outcrops at the same latitudinal belt, suggests a more humid climate in the lower part of the Miankuhi Formation, and correlates this part of the succession with a record of the Carnian Pluvial Episode. The sedimentological and stratigraphical analyses show an evolution from prodelta to delta setting in the upper Sina Formation, then an unconformity enhanced by an interval of fluvial deposits with histosol levels in the basal Miankuhi Formation, in correspondence with the hygrophytic assemblages. The unconformable boundary between the Miankuhi and the Sina formations is, consequently, interpreted as a result of the sea-level fall associated with the humid climate shift, occurring in close association with the first effects of the Eo

Peridotites of Ulten Zone (Eastern Alps, N Italy) show a transition from coarse protogranular spinel lherzolites to fine-grained amphibole + garnet peridotites, recorded by the crystallization of garnet coronas around spinel. Pyroxenite veins, transposed along the peridotite foliation, show a similar metamorphic evolution from coarse-grained (garnet-free) websterites to fine-grained garnet websterites. In both peridotites and websterites, garnet previously exsolved from porphyroclastic high-temperature pyroxenes and later crystallized along the foliation. This evolution has been interpreted to reflect cooling and pressure increase of websterites and host peridotites from spinel- to garnet-facies conditions. Microstructures and crystallographic orientation data indicate that the re-equilibration of garnet websterites in the garnet stability field occurred during deformation. Porphyroclastic pyroxenes have been interpreted to deform by dislocation glide and creep. In particular, TEM observations indicate the activation of the (100)[010] slip system in orthopyroxene. Core-and-mantle microstructures also suggest that dislocation creep was aided by subgrain rotation recrystallization, leading to the formation of neoblastic pyroxenes. These recrystallized grains deformed by diffusion-accommodated grain boundary sliding, as indicated by the occurrence of quadruple junctions and straight, aligned grain boundaries. The transition from dislocation creep to diffusion creep in websterites was accompanied by the crystallization of garnet along foliation, which triggered the pinning of the recrystallized matrix and stabilized the fine-grained microtexture for diffusion creep, promoting rheological weakening. Garnet websterites of Ulten Zone thus offer a unique opportunity to investigate the effects of reaction softening during the corner flow in the supra-subduction lithospheric mantle induced by the descending slab.

In the present work, we test the application of boat-camera-based photogrammetry as a tool for Virtual Outcrops (VOs) building on geological mapping and data collection. We used a 20 MPX camera run by an operator who collected pictures almost continuously, keeping the camera parallel to the ground and opposite to the target during a boat survey. Our selected target was the northern part of Santorini's caldera wall, a structure of great geological interest. A total of 887 pictures were collected along a 5.5-km-long section along an almost vertical caldera outcrop. The survey was performed at a constant boat speed of about 4 m/s and a coastal approaching range of 35.8 to 296.5m. Using the Structure from Motion technique we: i) produced a successful and high-resolution 3D model of the studied area, ii) designed high-resolution VOs for two selected caldera sections, iii) investigated the regional geology, iv) collected qualitative and quantitative structural data along the vertical caldera cliff, and v) provided a new VO building approach in extreme logistic conditions.

Fratture parallele a zone di rift con componenti di movimento trascorrente e obliquo, sviluppate in superficie e all’interno dei primi dieci chilometri della crosta, sono state documentate in contesti vulcano-tettonici estensionali attraverso il calcolo di meccanismi focali e la raccolta di dati di terreno di età olocenica. L’origine e lo sviluppo di queste strutture sono tuttora indefiniti: la presenza di componenti trascorrenti lungo fratture estensionali e faglie normali è infatti incompatibile con lo stato di stress all’origine di zone di rift, e, inoltre, una cinematica trascorrente lungo piani paralleli a faglie normali, come quella individuata, non risulta compatibile con i processi estensionali all’origine della formazione di un rift. Quest’anomalia è di estremo interesse per la comunità scientifica internazionale: infatti, interpretare correttamente dati geofisici associati alla risalita di magma, che causa la formazione di faglie e fratture estensionali in superficie, è fondamentale per un corretto monitoraggio di aree vulcaniche attive. Questa ricerca di dottorato si focalizza in particolare sul plateau vulcanico di Yellowstone, negli Stati Uniti occidentali, e sui rift del Theistareykir e Krafla, all’interno della Northern Volcanic Zone in Islanda nordorientale. Gli obiettivi principali sono l’individuazione di piani di faglia con diversa cinematica, lo studio delle relazioni temporali tra faglie trascorrenti/transtensive e faglie normali e tra faglie trascorrenti/transtensive ed intrusioni magmatiche, e l’analisi della variazione di cinematica con la profondità. Gli obiettivi sopra descritti sono stati raggiunti attraverso un approccio multidisciplinare, che consiste nell’integrazione tra nuovi dati sismologici e dati geologico-strutturali di terreno raccolti attraverso metodi classici e su ortomosaici e modelli digitali del terreno (DSMs) costruiti tramite tecniche di fotogrammetria applicate a rilievi con droni, e modelli numerici incentrati sul, Fractures with transcurrent and oblique components of motion, parallel and coeval to rift zones, which developed at the surface and in the upper ten kilometers of the crust, have been recently documented in extensional volcano-tectonic contexts through earthquake focal mechanisms and Holocene field data. Their origin and development is still undefined, due to the fact that transcurrent motions both along normal faults and extensional fractures are incompatible with the stress field associated with rift zones and, furthermore, transcurrent movements along planes parallel to normal faults are not compatible with the extension required to form a rift. This anomaly is an issue of international interest for the scientific community: in fact, interpreting correctly geophysical data associated with magma upwelling, which also influences the genesis of faults and extension fractures at the surface, is a key point when monitoring active volcanic zones. The present research focuses on the Yellowstone volcanic plateau, in the western United States, and the Theistareykir and Krafla Fissure Swarms, the westernmost rifts of the Northern Volcanic Zone, in northeast Iceland. Main aim is to define the partition of fault motions at planes with different kinematics, to study the temporal relations between transcurrent/transtensional faults and normal faults, to evaluate the relations between transcurrent/transtensional faults and magmatic intrusions and to analyze the variations of fault kinematics with depth. A multidisciplinary approach has been adopted, that consists in the integration of new geological-structural field data acquired through classical methods, quantitative data collected on Orthomosaics and on Digital Surface Models (DSMs) elaborated through Structure from Motion photogrammetry techniques (SfM) applied to Unmanned Aerial Vehicles (UAVs) surveys, seismic data regarding both earthquakes of magmatic and tectonic origin and numerical models on sill and dyke-induced def

A new, crustal-scale structural model aimed at illustrating the recent geometry of the western Greater Caucasus, has been built based on surface and subsurface data, in agreement with the theory of fault-related folds. The crustal-scale, structural cross-section shows that the western Greater Caucasus has a double vergence with a pro- and a retro-wedge actively propagating towards the Rioni foreland basins to the south and the Terek basin to the north. The retro-wedge and the Terek foreland basin developed on the upper plate, whereas the pro-wedge and the Rioni foreland basin developed on the lower, subducting plate. The formation of an antiformal stack in the axial zone of the western Greater Caucasus is related to reactivation of pre-existing normal faults during the orogeny. The main style of deformation within the pro-and retro-wedge is a series of fault-propagation and fault-bend folds, duplexes and structural wedges. Within the frontal part of the pro-and retro-wedge, a series of thrust-top basins developed.

In this paper, we describe the active kinematics of the Greater Caucasus (territories of Georgia, Azerbaijan and Russia) through an integrated analysis of seismological, geological-structural and GPS data. Alignments of crustal earthquake epicentres indicate that most seismic areas are located along the southern margin of the mountain belt and in its north-eastern sector, in correspondence of major, active WNW-ESE faults, parallel to the mountain range. Focal Mechanism Solutions (FMS) delineate dominant reverse fault kinematics in most sectors of the mountain belt, though swarms of strike-slip FMS indicate the presence of active transcurrent faulting, especially along the southeastern border of the Greater Caucasus. The mountain belt is characterized by dominant NNE-SSW-oriented P-axes. In the central-southern sector, in correspondence of the local collision between the Lesser and Greater Caucasus, P-axes are mainly NNW-SSE oriented. GPS data show dominant motions to the NNW, with rates increasing in eastward direction. All observations are consistent with a component of eastward escape of the central-eastern part of the Greater Caucasus.

We hereby provide an overview of four multi-year projects on geohazard assessment and mitigation, carried out under the umbrella of the North Atlantic Treaty Organization (NATO), with the involvement of more than 80 scientists coming from several countries, among which the US, Georgia, Italy, Russia, Azerbaijan. The projects have been aimed at enhancing the security of people and the safety of vital infrastructures as well as facilitating cooperation between scientists from NATO and non-NATO countries. The study areas are located in the Caucasus (Georgia), in Central Asia (Kyrgyzstan) and Northeast Asia (Kamchatka). Our work clearly demonstrates how Earth Science can contribute to improving scientific collaboration among countries that are politically in tension; moreover, geoscience can play a key role in preventing situations that may escalate into conflicts. This paper showcases the main results of the NATO-funded projects, both in terms of their scientific relevance and their geopolitical importance.