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Evidence of Paleogene subduction in the Western Mediterranean is scattered throughout high-pressure (HP) events in polymetamorphic basement terrains of disputed and differing provenance exposed along the margins of deep basins formed during Miocene to Quaternary slab retreat. The reconstruction of the original subduction geometry is often hindered by pervasive Miocene high-temperature (HT) ductile overprinting of earlier HP events. Here, we report rutile U¿Pb ages, EBSD-determined microstructures and thermodynamic modeling in eclogites from the upper-plate domain of the Betics (Ojén nappe, Alpujárride complex). These data show that the Ojén eclogite peak mineral assemblage formed during HP (1.3 ±0.15 GPa) and HT (700 ± 25 °C) ductile flow in the early Oligocene (30 ± 2.5 Ma). We interpret this event as a collisional phase linking Ojén eclogites to the Paleogene subduction of the western Tethys. Contrasting P¿T gradients of eclogites and arc volcanism between Corsica¿Calabria and Kabylies¿Betics point to a highly segmented orogenic system. NW¿SE-oriented transform faults separated a continental collision domain to the South from an oceanic subduction to the NE, with two subducting slabs ¿Calabrian and Algerian¿ retreating respectively towards the E and SE. Early Eocene inversion of the European and Maghrebian margins and ensuing early Oligocene collision resulted in (U)HP¿HT metamorphism in the Alpujárride and Kabylies. This orogen underwent extensional collapse in the late Oligocene-Aquitanian, before further shortening and the intracrustal emplacement of the Ronda peridotite. The upper plate Ojén eclogites and orogenic peridotites drifted westwards following the retreating Betics¿Rif Tethys slab in the early Miocene, after transform collapse that induced HP subduction of the SE Iberian margin below the Alpujárrides.

Cenozoic extension in the Western Mediterranean has been related to the dynamics of back-arc domains. Although, in most of its orogenic belts extension propagated into the fore-arc nappe domains. Here we revisit the structure, metamorphism and radiometric ages of the Tunisian Tell, where HP/LT rocks (350°C at 0.8 GPa), were exhumed by the sequential activity of extensional detachments after heating and decompression (410°C¿440°C at 0.6¿0.3 GPa) in a plate convergent setting. Normal faults thinning the Tunisian Tell detached at two different crustal levels. The shallower one cuts down into the Atlas Mesozoic sequence, involving Tellian Triassic evaporites in the hanging-wall forming halokinetic structures in the Mejerda basin late Miocene. The deeper-detachment bounds metamorphic domes formed by marbles and metapsammites from the Atlas domain. Illite crystallinity on Triassic rocks shows epizonal to anchizonal values, at deep and intermediate structural depths of the Tell-Atlas nappe belt, respectively. New U-Pb 49.78 ± 1.28 Ma rutile ages from Tellian metabasites, together with existing phlogopite 23¿17 Ma K-Ar ages in Atlas marbles from the footwall of the deepest detachment, indicate a polymetamorphic evolution. The Tell rocks underthrusted the Kabylian flysch in the early Eocene. Further, early Miocene shortening thrusted the metabasites over lower-grade sediments, producing HP/LT metamorphism and ductile stretching at the base of the Atlas belt. The exhumation of midcrustal roots of Western Mediterranean nappe belts after tectonic shortening is a common feature related to tearing at the edges of the subduction systems and inboard delamination of their subcontinental lithospheric mantle.

Paleogeographic reconstructions of the Western Mediterranean are often based on the present location of sedimentary outcrops. However, most geodynamic and biogeographic models for the region have highlighted the importance of up-to-hundreds of km of horizontal displacements of the terrains forming the western Mediterranean orogenic arcs since the early Miocene until the Pliocene. Here we update the known paleogeographic evolution for the westernmost Mediterranean, considering published biogeographic and recent new geological constraints, including paleontological, stratigraphic, tectonic kinematic data, seismic reflection lines, lowtemperature thermochronological dating, detrital zircon age populations, among others. During the Burdigalian to Langhian the rocks of the Betic hinterland, corresponding to the Alboran domain, where exhumed in a forearc setting as far East as Mallorca, now located 450 to 700 km of their present outcrops. Those exhuming rocks floored sedimentary basins among an island archipelago. The land connection between Mallorca and Alboran domains continued until the Serravallian as attested by the shared fossils of vertebrate insular fauna and biogeographic data of different taxa including trap-door spiders, beetles and fresh-water planarians. The westward migration of the Alboran forearc archipelago and its overlying basins (currently forming the Betic intramontane and western Alboran basins) was concomitant to the Langhian to Tortonian opening of the Algero-Balearic back-arc basin and the retreat of the Betic-Rif subducted slab. At a smaller scale, the Granada supra-detachment intramontane basin moved > 100 km between the Tortonian and Present, implying that previously interpreted, emerged domains, like the Sierra Nevada island where either inexistent or in a different location during the Tortonian. Sediment interpreted to represent marine gateways around and through the Alboran archipelago in the westernmost Mediterranean, may have being partial

[EN] The western Mediterranean hosts the plate boundary between the Eurasian and Nubian plates. These plates have a NW-SE convergence of 4.5 mm/year that currently controls the active deformation of the marine basins. In the westernmost basin, the Alboran Basin, the plate boundary has traditionally been understood as a zone of diffuse deformation in which there is no major structure accommodating most of the convergence. However, studies of the deep basin structure with multichannel seismic data reveal that the main submarine fault system in this basin, formed by the Alboran Ridge frontal thrust and the Yusuf strike-slip fault, accommodates at least half of the total plate convergence since the Miocene-Pliocene boundary, when they began their activity. This result challenges the diffuse deformation model, and has major implications for the assessment of the seismic and tsunamigenic hazard in the coastal areas, [ES] En el Mediterráneo occidental se encuentra el límite de placas entre las placas Eurasia y Nubia. Estas placas tienen una convergencia NO-SE de 4,5 mm/año, que actualmente controla la deformación activa de las cuencas marinas. En la cuenca más occidental, la cuenca de Alborán, el límite de placas tradicionalmente se ha entendido como una zona de deformación difusa en la que no había una estructura principal acomodando la deformación. Sin embargo, el estudio de la estructura profunda de la cuenca con datos de sísmica multicanal revelan que el principal sistema de fallas submarino en esta cuenca, formado por el frente de cabalgamiento del Alboran Ridge y la falla en dirección de Yusuf, acomoda un deslizamiento total superior a la mitad de la convergencia de placas desde el límite Mioceno-Plioceno, cuando comenzaron su actividad. Este resultado contradice el modelo de deformación difusa, y tiene grandes implicaciones para el análisis de riesgo sísmico y tsunamigénico de las zonas costeras

The Alboran Basin is located in the westernmost Mediterranean Sea. This basin was formed during the Miocene, and since the late Miocene, has been deformed due to the Iberia – Africa tectonic plates convergence, producing the contractive reorganization of some structures at the basin. Thus, the Alboran Basin is a seismically active area, which hosts the plate boundary between the European and African tectonic plates. This plate boundary has been traditionally considered a wide deformation zone, in which several small faults are accommodating the deformation. Based on a modern set of active seismic data, we were able for the first time to quantify the total slip accommodated by the most prominent tectonic structures of the area, late Miocene - early Pliocene in age. Our results show that the estimated total slip accommodated by the main fault systems may be similar (with error bounds) to the estimated plate convergence value since the Messinian time (~24 km). Thus, slip on that faults may have accommodated most of the Iberian – African plate convergence during the Plio-Quaternary, revealing that the contractive reorganization of the Alboran basin is focused on a few first-order structures that act as lithospheric boundaries, rather than widespread and diffuse along the entire basin. These results have implications not only for kinematic and geodynamic models, but also for seismic and tsunami hazard assessments. Using the most complete dataset until the date, we performed a revision of the geometry and characteristics of the main fault systems offshore. Based on this data, we perform a first appraisal of the seismogenic and tsunamigenic potential of the main fault systems offshore. Our simulations show that the seismogenic and tsunamigenic potential of the offshore structures of the Alboran Basin may be underestimated, and a further characterization of their associated hazard is needed

The Alboran Basin is located in the westernmost Mediterranean Sea. This basin was formed during the Miocene, and since the late Miocene, has been deformed due to the Iberia – Africa tectonic plates convergence, producing the contractive reorganization of some structures at the basin. Thus, the Alboran Basin is a seismically active area, which hosts the plate boundary between the European and African tectonic plates. This plate boundary has been traditionally considered a wide deformation zone, in which several small faults are accommodating the deformation. Based on a modern set of active seismic data, we were able for the first time to quantify the total slip accommodated by the most prominent tectonic structures of the area, late Miocene - early Pliocene in age. Our results show that the estimated total slip accommodated by the main fault systems may be similar (with error bounds) to the estimated plate convergence value since the Messinian time (~24 km). Thus, slip on that faults may have accommodated most of the Iberian – African plate convergence during the Plio-Quaternary, revealing that the contractive reorganization of the Alboran basin is focused on a few first-order structures that act as lithospheric boundaries, rather than widespread and diffuse along the entire basin. These results have implications not only for kinematic and geodynamic models, but also for seismic and tsunami hazard assessments. Using the most complete dataset until the date, we performed a revision of the geometry and characteristics of the main fault systems offshore. Based on this data, we perform a first appraisal of the seismogenic and tsunamigenic potential of the main fault systems offshore. Our simulations show that the seismogenic and tsunamigenic potential of the offshore structures of the Alboran Basin may be underestimated, and a further characterization of their associated hazard is needed

[EN] This Thesis analyses the tectonic evolution of Northern Tunisia from the Late Miocene to Present, using multiscale and multisource data analyses involving new technologies and approaches. Two orthogonal extensional systems with ENE- and SE-directed transport produced the extensional collapse of the Tell and Atlas thrust belts in northern Tunisia during the Late Miocene to Pliocene in a context of NW-SE plate convergence between Africa and Eurasia. This new hypothesis suggests for the first time the importance of crustal extension in the denudation of the Tunisian Atlas and Tell foreland thrust belts, which we related to deep mantle tectonic mechanisms, known as a common feature in other FTB´s in the western Mediterranean, i.e. Betics, Rif, Calabria and Apennines. Low-angle normal faults have extended and reworked the Tunisian Tell external foreland thrust belt, exhuming midcrustal epizonal Triassic metapelites and forming Late Miocene basins. This extension was followed by later Pliocene to Present tectonic inversion, developing the active shortening structures in Northern Tunisia. The main shortening structure is formed by different reverse and strike-slip fault segments, linked forming the 130 km long Alia-Thibar shear zone. Restored Plio- Quaternary deformation observed on reflection seismic lines indicates deformation rates around 0.6-0.8 mm/yr in the studied segments and larger amounts of shortening to the West of Northern Tunisia (16%) than to the East (7%), which suggests that tectonic inversion started earlier to the West and later propagated eastwards, reaching Northeastern Tunisia in the Late Pliocene. Due to the young age of tectonic this inversion, the present relief of Northern Tunisia is characteristic of a young thrust and fold belt, with dominating axial valleys along synforms and an incipient transverse drainage development propagating from West to East. New topographic development is favouring slope instabilities. Thus, in addition, we used a, [ES] En la presente Tesis doctoral analizamos la evolución tectónica del Norte de Túnez desde el Mioceno Superior hasta el presente, usando una metodología multidisciplinar que incluye el análisis tectónico y morfométrico de la región. El cinturón de pliegues y cabalgamientos del Tell tunecino fue adelgazado por dos sistemas extensionales ortogonales con transporte hacia el ENE y ESE, respectivamente, entre el Mioceneo Superior y el Plioceno en un contexto de convergencia NW-SE entre las placas Africana y Euroasiática. Esta nueva hipótesis sugiere por primera vez la importancia de la denudación extensional en el cinturón orogénico del Tell tunecino, en relación con mecanismos tectónicos profundos, como delaminación del manto litosférico subcontinental, descritos en otros cinturones de pliegues y cabalgamientos del Mediterráneo occidental como las Béticas, Rif, Calabria o los Apeninos. Fallas normales de bajo ángulo han extendido el cinturón de cabalgamientos exhumando rocas metamórficas situadas a la base del prisma orogénico a profundidades de corteza media, concomitántemente al desarrollo de cuencas sedimentarias del Mioceno Superior. Esta extensión fue seguida de una inversión tectónica contractiva desde el Plioceno, formándose las presentes estructuras transcurrentes y fallas inversas activas en el norte de Túnez. El principal zona de falla transcurrente de la region es la zona de falla de Alia-Thibar, con una longitud total de 130 km y compuesta por hasta 5 segmentos unidos, con diferente cinemática. La restauración del acortamiento observado en diversas lineas de sísmica de reflexión paralelas a la dirección de acortamiento indica tasas de acortamiento de 0,6-0,8 mm/año en los segmentos estudados y valores de acortamiento mayores al oeste de Tunez (16%) que hacia el este (7%). Esto podría indicar que la inversión tectónica se inició antes hacia el oeste y se ha propagado posteriormente hacia el este, afectando al NE de Túnez a partir del Plioceno superior. El

[ES] Nuestros estudios modifican sensiblemente y añaden mayor complejidad a los anteriores trabajos geodinámicos centrados en los relieves de la isla de Mallorca, focalizados casi exclusivamente en una fase compresiva oligo-miocena y en una posterior fase extensional en el Mioceno Medio como resultado de la relajación de la anterior., [EN] Our work significantly modifies and adds to the previous geodynamic studies focused on the tectonic evolution of the island of Mallorca.

Widespread overprinting of early high-pressure/low-temperature (HP/LT) subduction stages due to subsequent collisional or late-orogenic tectono-metamorphic events is a common feature affecting the interpretation of geochronologic data from HP/LT orogens. The Betic-Rif orogen is exemplary in this connection as a great majority of published radiometric ages are found to cluster around 20 Ma. This clustering is commonly interpreted as reflecting a short, yet complex, succession of tectono-metamorphic events spanning only over a few Myr, including back-arc extension and overthrusting of the Internal Zones on the External Zones. An alternative explanation consists in the poor preservation of a much earlier HP/LT metamorphic event, presumably Eocene, coeval with subduction and crustal thickening in the Internal Zones, and particularly the Alpujárride Complex. However, this age is vividly debated due to widespread resetting by the Early Miocene HT/LP overprint. In this study, we provide new Ar/Ar evidence from white micas selected along an E-W section of the Internal Betics, from the central to the eastern Alpujárride Complex. Our new data show (a) that exceptionally well-preserved HP/LT parageneses in this unit retain a well-defined Eocene age around 38 Ma, and (b) that widespread 20 Ma ages recorded all along the section correspond to a regional stage of exhumation, coeval with a major change in the kinematics of back-arc extension. Our study provides conclusive evidence that Ar/Ar dating of carefully targeted HP/LT associations can overcome the problem of extensive late-orogenic overprinting, testifying for an Eocene HP event around 38 Ma in the Betic-Rif orogen.

The current diffuse-strain model of the collision between Africa and Eurasia in the western Mediterranean predicts a broad region with deformation distributed among numerous faults and moderate-magnitude seismicity. However, the model is untested because most deformation occurs underwater, at poorly characterized faults of undetermined slip. Here we assess the diffuse-strain model analysing two active offshore fault systems associated with the most prominent seafloor relief in the region. We use pre-stack depth migrated seismic images to estimate, for the first time, the total Plio-Holocene slip of the right-lateral Yusuf and reverse Alboran Ridge structurally linked fault system. We show that kinematic restoration of deformational structures predicts a slip of 16 ± 4.7 km for the Alboran Ridge Fault and a minimum of 12 km for the Yusuf Fault. Thus, this fault system forms a well-defined narrow plate boundary that has absorbed most of the 24 ± 5 km Plio-Holocene Africa-Eurasia convergence and represents an underappreciated hazard

We study the structure of the Llevant ranges in Mallorca with special emphasis on the Cenozoic extensional evolution of the island, which we integrate in a new geodynamic model for the Westernmost Mediterranean. Mallorca underwent two Cenozoic rifting phases in the Oligocene and Serravallian, before and after the development of its Foreland Thrust Belt (FTB). The first extensional event produced Oligocene semigrabens (≈29–23 Ma) that were inverted during the Early-Middle Miocene (19–14 Ma) WNW-directed FTB development. The second rifting event produced the extensional collapse of the Mallorca FTB during the Serravallian (≈14–11 Ma). This later rifting was polyphasic, with two orthogonal extensional systems, producing first NE-SW, and then NW-SE extension. The Oligocene extension affected a major part of the Western Mediterranean, opening the Liguro-Provençal and other basins after the collapse of the Palaeogene AlKaPeCa orogen, and Mallorca, its former hinterland. Continued plate convergence nucleated a new subduction system in the Early Miocene that initiated along the Ibiza transform, producing the Mallorca WNW-directed FTB and subduction of the South-East Iberian passive margin. This process individualized the Betic-Rif slab and initiated its westward retreat. Serravallian extension occurred at the northern edge of the subduction system coeval to the Algero-Balearic basin opening. Extension initiated toward the SW direction of slab tearing and later rotated to a NW-SE direction, probably in response to flexural and isostatic rebound. Through these processes the Alboran domain archipelago was driven toward the southwest until the Late Miocene, contributing to the present isolation of Mallorca from its Betic hinterland.

Based on more than 4,500 km of new and re-processed multichannel seismic lines, high-resolution seafloor bathymetry, available well data, and basement dredge samples, we have re-evaluated the entire stratigraphy and the tectonic evolution of the Alboran and western Algerian basins. We have correlated the sediment units deposited since the beginning of the formation of the different sub-basins, and we present for the first time a coherent stratigraphy and large-scale tectonic evolution of the whole region. The results provide the information to test and refine models of the geodynamic evolution of the westernmost Mediterranean. The data analysis supports an independent evolution of the sub-basins through the latemost Oligocene and Miocene, and a common Plio-Holocene evolution. The latemost Oligocene and Miocene evolution was controlled by the evolution of the Gibraltar subduction system. The oldest sedimentary unit is restricted to the West Alboran and Malaga basins depocenter that during the latemost Oligocene and early Miocene connected to some smaller marine basins currently uplifted and located onshore on the Betics range. Later, during the middle Miocene, the Habibas and Pytheas sub-basins formed a second depocenter on the North African margin. The different sedimentary units found in both depocenters, together with their different deformation patterns, support that the West Alboran-Malaga and the Habibas-Pytheas depocenters were separated by a major tectonic boundary. The early Tortonian initial arc magmatic activity produced the formation of new areas floored by a volcanic basement by the end of the late Tortonian, when the first sedimentary units deposited in the East Alboran sub-basin, and probably during the late Tortonian-early Messinian in the South Alboran sub-basin. Extension of the back-arc setting created oceanic crust flooring the Algero Balearic Basin. The extensional formation of the westernmost Mediterranean basins ended in the latemost Miocene. T

Exploration of territories not previously analyzed by landslide experts provides interesting findings. The Chgega landslide, in northern Tunisia, represents a paradigmatic mass movement. It can be classified as a complex landslide, or more specifically as vast rock spreading that evolved into a block slide. It involves a great block of limestone—about 900 m long and 400 m wide—sliding over ductile clays and marls. The viscoplastic creep of the clays drives the landslide and creates, in its crown, a graben ~800 m long and ~120 m wide that breaks the summit of Chgega Mountain. Using Interferometric Synthetic Aperture Radar (InSAR) technologies, we demonstrate that this complex landslide is currently active and moreover shows progressive movement without clear episodic accelerations. The velocity of the limestone block is just above 2 mm/yr. The occurrence of gravity-induced joints indicates that the movement has an orientation towards 333° of azimuth on average, conditioned by the landscape around Chgega. These results were obtained through the analysis of a 3D model and a high-resolution orthoimage created from photographs acquired by an Uncrewed Aerial Vehicle (UAV). We may conclude that the landslide movement is determined by normal faults with directions N060°E and N140–150°E. This characterization of the Chgega landslide can serve as the basis for future studies about the origin of this slope movement. Furthermore, the data provided here may support the recognition of Chgega as a singular geological point that deserves to be declared a geosite.