Tectonics of the wedge-top Epiligurian basins and implications for the syn-to-post orogenic evolution of the Northern Apennines fold-and-thrust belt (Italy)

This thesis has the aim to give an overview about the tectonic history of the Epiligurian units, which crop out in the axial portion of the Northern Apennines fold-and-thrust belt, from a structural and thermal point of view, through a multiscalar and multitecnique approach. I focused on a key example of Epiligurian wedge-top basin, (Marzabotto Basin) proceeding from macro-to-microscale approach. The study started from a remote sensing analysis of the lineaments and morphostructures which affected the study area to obtain the regional faulting pattern and an overview about the main tectonic structures, used as basis for the structural investigation at the mesoscale. On the basis of this, it was possible to reconstruct the succession of tectonic events that affected the Marzabotto Basin, consisting in: i) two sets of thrusts indicating a NE-SW and NW-SE shortening of the sedimentary succession; ii) NE-SW-left lateral transtensional faults related to a strike-slip tectonic phase; iii) three main sets of extensional structures which cut and displace the previous thrusts. Normal faults are related to the post-orogenic evolution and have been dated with U-Th method, getting an age of Middle-Late Pleistocene. From a thermal point of view, apatite fission-tracks and (U-Th)/He analyses of detrital minerals and thermal modelling on the middle-upper Eocene siliciclastic deposits allowed me to better constrain the local exhumation history and correlate it with the large-scale tectonic evolution of the Northern Apennines. In particular, the Marzabotto Basin experienced a complex burial-exhumation history, consisting in two cooling cooling phases related to the growth of the Northern Apennines belt (Oligo-Miocene in age) and a later cooling which tracks the accretion in the orogenic wedge concomitant with rollback-driven extension (late Miocene-Pliocene in age). In conclusion it is possible to affirm that the study shed new light on poorly constrained elements of fold-and-thrust belt.

Deep geometry of subduction below the Andean belt of Colombia as revealed by seismic tomography

In this study new tomographic models of Colombia were calculated. I used the seismicity recorded by the Colombian seismic network during the period 2006-2009. In this time period, the improvement of the seismic network yields more stable hypocentral results with respect to older data set and allows to compute new 3D Vp and Vp/Vs models. The final dataset consists of 10813 P- and 8614 S-arrival times associated to 1405 earthquakes. Tests with synthetic data and resolution analysis indicate that velocity models are well constrained in central, western and southwestern Colombia to a depth of 160 km; the resolution is poor in the northern Colombia and close to Venezuela due to a lack of seismic stations and seismicity. The tomographic models and the relocated seismicity indicate the existence of E-SE subducting Nazca lithosphere beneath central and southern Colombia. The North-South changes in Wadati-Benioff zone, Vp & Vp/Vs pattern and volcanism, show that the downgoing plate is segmented by slab tears E-W directed, suggesting the presence of three sectors. Earthquakes in the northernmost sector represent most of the Colombian seimicity and concentrated on 100-170 km depth interval, beneath the Eastern Cordillera. Here a massive dehydration is inferred, resulting from a delay in the eclogitization of a thickened oceanic crust in a flat-subduction geometry. In this sector a cluster of intermediate-depth seismicity (Bucaramanga Nest) is present beneath the elbow of the Eastern Cordillera, interpreted as the result of massive and highly localized dehydration phenomenon caused by a hyper-hydrous oceanic crust. The central and southern sectors, although different in Vp pattern show, conversely, a continuous, steep and more homogeneous Wadati-Benioff zone with overlying volcanic areas. Here a "normalthickened" oceanic crust is inferred, allowing for a gradual and continuous metamorphic reactions to take place with depth, enabling the fluid migration towards the mantle wedge.

The effect of osmolytes on protein fold stability at the single-molecule level

By pulling and releasing the tension on protein homomers with the Atomic Force Miscroscope (AFM) at different pulling speeds, dwell times and dwell distances, the observed force-response of the protein can be fitted with suitable theoretical models. In this respect we developed mathematical procedures and open-source computer codes for driving such experiments and fitting Bell’s model to experimental protein unfolding forces and protein folding frequencies. We applied the above techniques to the study of proteins GB1 (the B1 IgG-binding domain of protein G from Streptococcus) and I27 (a module of human cardiac titin) in aqueous solutions of protecting osmolytes such as dimethyl sulfoxide (DMSO), glycerol and trimethylamine N-oxide (TMAO). In order to get a molecular understanding of the experimental results we developed an Ising-like model for proteins that incorporates the osmophobic nature of their backbone. The model benefits from analytical thermodynamics and kinetics amenable to Monte-Carlo simulation. The prevailing view used to be that small protecting osmolytes bridge the separating beta-strands of proteins with mechanical resistance, presumably shifting the transition state to significantly higher distances that correlate with the molecular size of the osmolyte molecules. Our experiments showed instead that protecting osmolytes slow down protein unfolding and speed-up protein folding at physiological pH without shifting the protein transition state on the mechanical reaction coordinate. Together with the theoretical results of the Ising-model, our results lend support to the osmophobic theory according to which osmolyte stabilisation is a result of the preferential exclusion of the osmolyte molecules from the protein backbone. The results obtained during this thesis work have markedly improved our understanding of the strategy selected by Nature to strengthen protein stability in hostile environments, shifting the focus from hypothetical protein-osmolyte interactions to the more general mechanism based on the osmophobicity of the protein backbone.

Characterization of fold-related fractures in the carbonate rocks of the Cingoli anticline, northern Apennines, Italy

Thrust fault-related folds in carbonate rocks are characterized by deformation accommodated by different structures, such as joints, faults, pressure solution seams, and deformation bands. Defining the development of fracture systems related to the folding process is significant both for theoretical and practical purposes. Fracture systems are useful constrains in order to understand the kinematical evolution of the fold. Furthermore, understanding the relationships between folding and fracturing provides a noteworthy contribution for reconstructing the geodynamic and the structural evolution of the studied area. Moreover, as fold-related fractures influence fluid flow through rocks, fracture systems are relevant for energy production (geothermal studies, methane and CO2 , storage and hydrocarbon exploration), environmental and social issues (pollutant distribution, aquifer characterization). The PhD project shows results of a study carried out in a multilayer carbonate anticline characterized by different mechanical properties. The aim of this study is to understand the factors which influence the fracture formation and to define their temporal sequence during the folding process. The studied are is located in the Cingoli anticline (Northern Apennines), which is characterized by a pelagic multilayer characterized by sequences with different mechanical stratigraphies. A multi-scale analysis has been made in several outcrops located in different structural positions. This project shows that the conceptual sketches proposed in literature and the strain distribution models outline well the geometrical orientation of most of the set of fractures observed in the Cingoli anticline. On the other hand, the present work suggests the relevance of the mechanical stratigraphy in particular controlling the type of fractures formed (e.g. pressure solution seams, joints or shear fractures) and their subsequent evolution. Through a multi-scale analysis, and on the basis of the temporal relationship between fracture sets and their orientation respect layering, I also suggest a conceptual model for fracture systems formation.

Understanding block rotation of strike-slip fault zones: Paleomagnetic and structural approach

This thesis is focused on the paleomagnetic rotation pattern inside the deforming zone of strike-slip faults, and the kinematics and geodynamics describing it. The paleomagnetic investigation carried out along both the LOFZ and the fore-arc sliver (38º-42ºS, southern Chile) revealed an asymmetric rotation pattern. East of the LOFZ and adjacent to it, rotations are up to 170° clockwise (CW) and fade out ~10 km east of fault. West of the LOFZ at 42ºS (Chiloé Island) and around 39°S (Villarrica domain) systematic CCW rotations have been observed, while at 40°-41°S (Ranco-Osorno domain) and adjacent to the LOFZ CW rotations reach up to 136° before evolving to CCW rotations at ~30 km from the fault. These data suggest a directed relation with subduction interface plate coupling. Zones of high coupling yield to a wide deforming zone (~30 km) west of the LOFZ characterized by CW rotations. Low coupling implies a weak LOFZ and a fore-arc dominated by CCW rotations related to NW-sinistral fault kinematics. The rotation pattern is consistent with a quasi-continuous crust kinematics. However, it seems unlikely that the lower crust flux can control block rotation in the upper crust, considering the cold and thick fore-arc crust. I suggest that rotations are consequence of forces applied directly on both the block edges and along the main fault, within the upper crust. Farther south, at the Austral Andes (54°S) I measured the anisotropy of magnetic susceptibility (AMS) of 22 Upper Cretaceous to Upper Eocene sites from the Magallanes fold-thrust belt internal domains. The data document continuous compression from the Early Cretaceous until the Late Oligocene. AMS data also show that the tectonic inversion of Jurassic extensional faults during the Late Cretaceous compressive phase may have controlled the Cenozoic kinematic evolution of the Magallanes fold-thrust belt, yielding slip partitioning.

Subsidence history, thermal maturity, and structural inversion of the Greater Caucasus-Kura-Adjara-Trialeti basin system of central-eastern Georgia

This study aims at defining the tectonic evolution of a portion of the Caucasian region, in Georgia, which experienced a complex pattern of deformation events throughout Mesozoic and Cenozoic times. An integrated approach was applied to unravel the thermo-tectonic history of three inverted sedimentary basins from burial to exhumation. Additionally, this dissertation provides examples of structural inversion of sedimentary basins in response to far-field transmission of compressional stresses away from collision zones, contributing to elucidate the dynamics of stress partitioning during continental collisions. The Adjara-Trialeti fold-and-thrust belt in south-western Georgia results from the structural inversion of a Middle Eocene continental back-arc rift basin opened as a consequence of the Northern Neotethys slab rollback. This study quantitatively defines the subsidence and exhumation history of the Adjara-Trialeti basin, constraining its Middle Miocene inception of structural inversion. The western Kura Basin is a flexural foreland basin trapped between the Lesser Caucasus to the south and the Greater Caucasus to the north. This study constrains successive and competing episodes of flexural subsidence during Oligocene-Miocene times, followed by partial inversion through thick- and thin-skinned tectonics in response to continued convergence between the adjacent, oppositely verging orogenic belts. The Greater Caucasus results from the structural inversion of a Jurassic continental back-arc basin, but the timing of its growth is still debated. An across-strike transect in its southern central domain was studied, indicating that this sector of the Greater Caucasus experienced two phases of structural inversion during Late Cretaceous-Paleocene and Late Miocene times. Overall, the dataset presented in this dissertation points to a complex and episodic history of incremental deformation, characterised by successive phases of extensional and compressional tectonics which developed in response to sequential terrane accretion at the southwestern margin of Eurasia since Late Cretaceous times, eventually determining the current configuration of the Arabia-Eurasia collision zone.

Landslide susceptibility in the Belt and Road Initiative

The Belt and Road Initiative (BRI) is a project launched by the Chinese Government whose main goal is to connect more than 65 countries in Asia, Europe, Africa and Oceania developing infrastructures and facilities. To support the prevention or mitigation of landslide hazards, which may affect the mainland infrastructures of BRI, a landslide susceptibility analysis in the countries involved has been carried out. Due to the large study area, the analysis has been carried out using a multi-scale approach which consists of mapping susceptibility firstly at continental scale, and then at national scale. The study area selected for the continental assessment is the south-Asia, where a pixel-based landslide susceptibility map has been carried out using the Weight of Evidence method and validated by Receiving Operating Characteristic (ROC) curves. Then, we selected the regions of west Tajikistan and north-east India to be investigated at national scale. Data scarcity is a common condition for many countries involved into the Initiative. Therefore in addition to the landslide susceptibility assessment of west Tajikistan, which has been conducted using a Generalized Additive Model and validated by ROC curves, we have examined, in the same study area, the effect of incomplete landslide dataset on the prediction capacity of statistical models. The entire PhD research activity has been conducted using only open data and open-source software. In this context, to support the analysis of the last years an open-source plugin for QGIS has been implemented. The SZ-tool allows the user to make susceptibility assessments from the data preprocessing, susceptibility mapping, to the final classification. All the output data of the analysis conducted are freely available and downloadable. This text describes the research activity of the last three years. Each chapter reports the text of the articles published in international scientific journal during the PhD.