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The Zagros Fold and Thrust Belt (ZFTB) is an outstanding orogen running from eastern Turkey to the Makran area. It is formed as a consequence of the convergence between the Arabian and the Eurasian plates that occurred in the Neogene. This still active and long-lasting process generated a topographic configuration dominated by a series of parallel folding structures which, at places, isolate internal basins. The topographic configuration has, in turn, profoundly influenced the river network evolution, which follows a trellis pattern with the main valleys developed in the synclines and rivers that occasionally cut into anticlines. The peculiar climate, characterised by arid and semi-arid conditions, makes most of the rivers ephemeral, alimented only by short rainfall events. For this reason, the sediments are transported over short distances and deposited in huge alluvial fans. Although the Zagros is one of the most studied belts in the world, its tectonic evolution is far from being fully understood. Debated, for example, are the beginning of collision, the primary deformation mechanism, the evolution of the drainage system, the formation process of the alluvial fans, and the interrelations between landscape, tectonics, and climate. This paper, focusing on the geodynamic, geological, stratigraphic, and topographic configuration of the Zagros belt, is intended to be a compendium of the most up-to-date knowledge on the Zagros and aims to provide the cognitive basis for future research that can find answers to outstanding questions.

Widespread wrench tectonics have been described along the northern Andes. The Bucaramanga fault, described as sinistral strike-slip, bounds the high Santander Massif. We combine structural and thermochronological data from the central-southern portion of the fault to investigate the vertical displacement. The structural survey data show old phases of activity preserved in the host rocks along the fault trace, with the superimposition of different generations of slickenlines, and both strike-slip and dip-slip kinematics indicators. New and previous thermochronological data show that differential exhumation of the fault walls has been ongoing for the last 50 Ma. The hanging wall, the Santander Massif, records, in the central portion, decreasing exhumation rates from the early Miocene to the mid- to late Miocene and, in the southern portion, constant rates from the Late Oligocene to the Pliocene. Combining such observations, the thermochronological offset resulting from the relative motion of the two fault walls is comparable with the observed drop in elevation across the fault, suggesting that the present topography of the Santander Massif is related to vertical movement along the Bucaramanga fault. We infer that the fault has a significant Neogene reverse component, consistent with the present day horizontal global positioning system vector data, long-term exhumation rates and the structural assemblage. Supplementary Material: The Supplementary Materials contain methodological information on the thermochronological procedures, a compilation of the previously published data used in this study and the structural geology dataset, https://doi.org/10.6084/m9.figshare.c.4620140 [ABSTRACT FROM AUTHOR]

The Nile is the longest river on Earth and has persisted for millions of years. It has been suggested that the Nile in its present path is ~6 million years old, whereas others argue that it may have formed much earlier in geological history. Here we present geological evidence and geodynamic model results that suggest that the Nile drainage has been stable for ~30 million years. We suggest that the Nile’s longevity in essentially the same path is sustained by the persistence of a stable topographic gradient, which in turn is controlled by deeper mantle processes. We propose that a large mantle convection cell beneath the Nile region has controlled topography over the last 30 million years, inducing uplift in the Ethiopian–Yemen Dome and subsidence in the Levant Sea and northern Egypt. We conclude that the drainage system of large rivers and their evolution over time can be sustained by a dynamic topographic gradient.

Unraveling the evolution of supradetachment basins developed in the hanging wall of low‐angle detachment faults may be an invaluable tool in reconstructing the tectonic evolution of highly extended terrains. These basins may record major regional tectonic events related to the exhumation of metamorphic core complexes, and the reconstruction of their evolution helps to quantify the amount of extension accommodated by such processes. Here we present stratigraphic and structural field evidence and micropaleontological constraints to the Neogene‐to‐Quaternary evolution of the supradetachment Gediz Graben that developed on top of the exhuming Central Menderes Massif (SW Turkey). This basin displays three different structural styles during its evolution: (i) it initiated as a ramp basin following the activation of the Gediz Detachment in the Middle Miocene, (ii) evolved as a half graben during the late Miocene following the activation of high‐angle brittle faults at its southern margin, and (iii) reached its final symmetric graben configuration in Late Pliocene (?)‐Quaternary times following the activation of its northern margin. New micropaleontological data document a short‐lived upper Tortonian marine episode in the basin, and major along‐strike variations in exhumation are documented on its southern margin. Our reconstruction shows how sedimentary basins originally formed in the hanging wall of detachment faults may eventually end up in tectonic contact with the mylonitic footwall. Finally, we highlight the importance of magmatism in localizing the deformation in highly extended terrains and in controlling the evolution of supradetachment systems. The spatiotemporal ductile‐to‐brittle evolution of the Gediz detachment controls the tectonostratigraphic evolution of the Gediz GrabenAn upper Tortonian marine transgression is recorded in the sedimentary fill of the Gediz GrabenBasins developed in the hanging wall of detachment faults may eventually end up in tectonic contact with the mylonitic footwall

The study of slab‐slab interactions has come to the front of geodynamics researches to explain geological and geophysical observations from tectonically complex areas. Here we aim to better understand the geodynamics of the Central Mediterranean, where the Adria plate subducts on its two opposite sides. Additionally, the slab below the Central South Apennines has been progressively breaking off during the last 3 Myr. The role of a slab window in a single slab or in an outward dipping double‐sided subduction system is addressed by analog models at the scale of the upper mantle, realized using glucose syrup and silicone putty, to model the interaction between the Earth's mantle and the lithosphere. Our results show that the presence of a slab window modifies the pattern of mantle circulation, as well as the trench geometry and kinematics. In particular, the opening of the slab window induces the formation of two arcs flanking the window, while the mantle flows through it and turns toward the arcs, creating a small‐scale toroidal flow. The effect of a slab window is more pronounced on double subduction systems, as the outflow through the window is amplified, while internal deformation is induced in the plate by the opposite slab pull force. These experimental results suggest that the origin of the Apenninic and the Calabrian arcs is the result of the formation of a slab window, providing a new interpretation of the surface deformation and the SKSshear wave splitting pattern of the Adria microplate. The Adria microplate in the Central Mediterranean is an important part of the tectonic puzzle between the converging Africa and Eurasia plates. The heavy lithosphere sinks into the underlying mantle on two sides of the Adria plate, under the Apennines in the west and under the Dinarides in the east. During the most recent few millions of years, the lithosphere started to detach from the surface in the Central South Apennines while sinking into the mantle. This opened a slab window, an additional escape route for the mantle, which is squeezed by the two subducting lithospheres. We scaled down and simplified this setting in order to model and investigate the role of the dual subduction and the opening slab window in the evolution of the Central Mediterranean by means of analog models. Our results show that the two opposite subduction zones have a regional tectonics effect via the complex subduction‐induced mantle circulation. Furthermore, the detaching lithosphere modifies the geometry of the subduction zone, which results in a double‐arc geometry resembling the Northern Apennines and Calabria. The combination of slab‐slab interactions and an opening slab window defines the recent tectonic evolution of the Central MediterraneanOutward dipping double‐sided subduction drives the mantle to flow from below the Adria plate toward the Alps and the Pannonian BasinThe opening of a slab window under the Central Apennines changes the trench geometry and the subduction‐induced mantle flow pattern

The formation of mountain belts or rift zones is commonly attributed to interactions between plates along their boundaries, but the widely distributed deformation of Asia from Himalaya to the Japan Sea and other back‐arc basins is difficult to reconcile with this notion. Through comparison of the tectonic and kinematic records of the last 50 Ma with seismic tomography and anisotropy models, we show that the closure of the former Tethys Ocean and the extensional deformation of East Asia can be best explained if the asthenospheric mantle transporting India northward, forming the Himalaya and the Tibetan Plateau, reaches East Asia where it overrides the westward flowing Pacific mantle and contributes to subduction dynamics, distributing extensional deformation over a 3,000‐km wide region. This deep asthenospheric flow partly controls the compressional stresses transmitted through the continent‐continent collision, driving crustal thickening below the Himalayas and Tibet and the propagation of strike‐slip faults across Asian lithosphere further north and east, as well as with the lithospheric and crustal flow powered by slab retreat east of the collision zone below East and SE Asia. The main shortening direction in the deforming continent between the collision zone and the Pacific subduction zones may in this case be a proxy for the direction of flow in the asthenosphere underneath, which may become a useful tool for studying mantle flow in the distant past. Our model of the India‐Asia collision emphasizes the role of asthenospheric flow underneath continents and may offer alternative ways of understanding tectonic processes. The collision of India with Asia has induced the propagation of continent‐scale faults to large distances from the Himalayas, all the way to the margins of Asia where back‐arc basins, such as the Japan Sea, formed above the subductions of the Pacific and Indian Oceans. The respective roles of collision and subduction in controlling the deformation of Asia at such long distances are not well understood. Based on a comparison of kinematic trajectories of lithospheric plates and blocks since 50 Ma with mantle flow directions inferred from seismological data, we propose that the connection between collision and back‐arc extension is made by the asthenosphere flowing underneath. This flowing mantle comes from an upwelling zone below South Africa and has pushed India inside Asia along more than 3,000 km after the first collision. The flow then invaded Asia all the way to the subduction trenches where it followed the retreat of the subducting lithospheres, controlling the geometry and kinematics of the major strike‐slip faults and back‐arc basins. This possible control of continental deformation by the asthenosphere flowing underneath is a different view of continental deformation and may offer a way of studying mantle flow below continents in the distant past. Coeval India‐Asia collision and Pacific back‐arc extension explained by asthenospheric flowMantle flow correlates with long‐term kinematics from India to Pacific borderIndian mantle reaches Pacific border and Asian lithosphere spreads above ponding slabs

Active and fossil subduction systems consisting of two adjacent plates with opposite retreating directions occur in several areas on Earth, as the Mediterranean or Western Pacific. The goal of this work is to better understand the first‐order plate dynamics of these systems using the results of experimental models. The laboratory model is composed of two separate plates made of silicon putty representing the lithosphere, on top of a tank filled with glucose syrup representing the mantle. The set of experiments is designed to test the influence of the width of plates and the initial separation between them on the resulting trench velocities, deformation of plates, and mantle flow. Results show that the mantle flow induced by both plates is asymmetric relative to the axis of each plate causing a progressive merging of the toroidal cells that prevents a steady state phase of the subduction process and generates a net outward drag perpendicular to the plates. Trench velocities increase when trenches approach each other and decrease when they separate after their intersection. The trench curvature of both plates increases linearly with time during the entire evolution of the process regardless their width and initial separation. The interaction between the return flows associated with each retreating plate, particularly in the interplate region, is stronger for near plate configurations and correlates with variations of rollback velocities. We propose that the inferred first‐order dynamics of the presented analog models can provide relevant clues to understand natural complex subduction systems. Mantle flow induced by opposed adjacent plates is asymmetrical showing a progressive merging of the toroidal cells when trenches approachTrench retreat velocities are not steady and increase/decrease while trenches approach/separateThe first‐order consequences of the dynamics of double subduction systems are relevant in natural scenarios

The Apennines is a well‐studied orogeny formed by the accretion of continental slivers during the subduction of the Adriatic plate, but its deep structure is still a topic of controversy. Here we illuminated the deep structure of the Northern Apennines belt by combining results from the analysis of active seismic (CROP03) and receiver function data. The result from combining these two approaches provides a new robust view of the structure of the deep crust/upper mantle, from the back‐arc region to the Adriatic subduction zone. Our analysis confirms the shallow Moho depth beneath the back‐arc region and defines the top of the downgoing plate, showing that the two plates separate at depth about 40 km closer to the trench than reported in previous reconstructions. This spatial relationship has profound implications for the geometry of the shallow subduction zone and of the mantle wedge, by the amount of crustal material consumed at trench. Depicting the structure of the Earth is a goal for all Earth scientists. Knowledge of the Earth's properties is fundamental for a number of societal challenges, from locating georesources to the mitigation of seismic risk. We investigate the structure of the Earth's crust beneath a well‐studied subduction orogeny, the Apennines (Italy), analyzing together different seismic data sets. The Apennines mountain chain were the locus of a number of middle‐ to high‐magnitude seismic sequences in the last few years. Our findings will be a necessary step forward in defining the active processes in the Earth's interior and in defining the seismic risk of the area. The combination of passive and active seismic data provides a robust image of the deep structure of crust and lithosphereBeneath the N. Apennines, the mantle wedge is located beneath the topography divide, 40 km eastward with respect to previous estimateOnly one third of the Adriatic crust is accreted in the orogenic wedge, while the rest descend down to deeper depth

Transpressional margins are widespread, and their dynamics are relevant for plate boundary evolution globally. Though transpressional orogen evolution involves a topographic response to deformation, many studies focus only on the structural development of the system ignoring surface processes. Here, we present a new set of analog models constructed to investigate how tectonic and surface processes interact at transpressive plate boundaries and shape topography. Experiments are conducted by deforming a previously benchmarked crustal analog material in a meter‐scale plexiglass box while controlling erosion through misting nozzles mounted along the transpressional wedge. To analyze the experiments, we generate digital elevation models from laser scans and conduct image correlation analysis on photos taken during experiments. We focus on three experiments that cover a range of erosional conditions and shortening stages (two end‐member erosion models and a dry reference). In all experiments, a bivergent wedge forms, and strain partitioning broadly evolves according to previously established models. Regarding drainage networks, we find that the streams in our models develop differently through feedback between fault development and drainage rearrangement processes. Differences between end‐member erosional models can be explained by the varying response of streams to structure modulated by rainfall. Additionally, erosion may influence the structural evolution of transpressional topography, leading to accelerated strike‐slip partitioning. From these results, we create a model for developing structures, streams, and topography where incision and valley formation along main structures localize exhumation. We apply insights from the models to natural transpressional systems, including the Transverse Ranges, CA, and the Venezuelan Andes. Feedback between fault and drainage network development regulates the deformation, exhumation, and morphology of transpressional systemsIncreased erosion accelerates the progression from distributed deformation to complete strike‐slip strain partitioningDue to heightened rock uplift and incision, the maximum exhumation in a transpressional wedge is along the master fault and axial valley Feedback between fault and drainage network development regulates the deformation, exhumation, and morphology of transpressional systems Increased erosion accelerates the progression from distributed deformation to complete strike‐slip strain partitioning Due to heightened rock uplift and incision, the maximum exhumation in a transpressional wedge is along the master fault and axial valley

Orogenic plateaus of continental collision zones exhibit landforms and fluvial networks that retain first‐order information on their topographic evolution and vertical growth. The inversion of river longitudinal profiles allows to reconstruct the base level fall history of plateaus, supporting the study of landscape evolution in the frame of geodynamic models. The Eastern Anatolian Plateau (EAP) of the Arabia‐Eurasia collision zone is a plateau at an early stage of development. It stands at ∼2,000 m, presents endorheic basins, and is drained by three main river networks. Seismic data indicate a thinned lithospheric mantle that explains the late Cenozoic volcanic activity. Despite the number of studies on the EAP uplift, its history is still debated. In this study we investigated the EAP hydrography and topography, and we inverted the longitudinal profile of one of the main rivers: the Arax River. The results describe a high‐standing, low‐relief plateau drained by a hydrography, controlled by active tectonics. Longitudinal profiles and χ‐plots illustrate rivers in disequilibrium with channel steepness increasing downstream. The elevation of marine deposits indicates a surface uplift of ∼2,000 m, ∼500 m of which are of residual topography. This upheaval occurred by two increases: the first one at 10–11 Ma with the opening of a slab window and the arrival of a mantle flow from Arabia and the second one at ∼5 Ma with the continued inflow coupled with isostasy. Our results describe the early stage of collisional plateau development, distinguishing the contribution of deep processes and isostasy to the topographic growth. The Eastern Anatolian Plateau (EAP) is a continent‐continent collisional plateau at an early stage of developmentThe EAP was affected by a surface uplift of ∼2,000 m according to geologic and geomorphic data; ∼500 m of it are dynamically supportedThe base level fall history of EAP documents a three steps increase in uplift rate due to the contribution of deep and crustal processes The Eastern Anatolian Plateau (EAP) is a continent‐continent collisional plateau at an early stage of development The EAP was affected by a surface uplift of ∼2,000 m according to geologic and geomorphic data; ∼500 m of it are dynamically supported The base level fall history of EAP documents a three steps increase in uplift rate due to the contribution of deep and crustal processes

Collision with and subduction of an oceanic plateau is a rare and transient process that usually leaves an indirect imprint only. Through a tectonostratigraphic analysis of pre‐Oligocene sequences in the San Jacinto fold belt of northern Colombia, we show the Late Cretaceous to Eocene tectonic evolution of northwestern South America upon collision and ongoing subduction with the Caribbean Plate. We linked the deposition of four fore‐arc basin sequences to specific collision/subduction stages and related their bounding unconformities to major tectonic episodes. The Upper Cretaceous Cansona sequence was deposited in a marine fore‐arc setting in which the Caribbean Plate was being subducted beneath northwestern South America, producing contemporaneous magmatism in the present‐day Lower Magdalena Valley basin. Coeval strike‐slip faulting by the Romeral wrench fault system accommodated right‐lateral displacement due to oblique convergence. In latest Cretaceous times, the Caribbean Plateau collided with South America marking a change to more terrestrially influenced marine environments characteristic of the upper Paleocene to lower Eocene San Cayetano sequence, also deposited in a fore‐arc setting with an active volcanic arc. A lower to middle Eocene angular unconformity at the top of the San Cayetano sequence, the termination of the activity of the Romeral Fault System, and the cessation of arc magmatism are interpreted to indicate the onset of low‐angle subduction of the thick and buoyant Caribbean Plateau beneath South America, which occurred between 56 and 43 Ma. Flat subduction of the plateau has continued to the present and would be the main cause of amagmatic post‐Eocene deposition. We linked Upper Cretaceous to Eocene tectonostratigraphic evolution of the San Jacinto fold belt of NW Colombia with plate kinematicsEocene major change in plate kinematics caused to the onset of flat subduction and cessation of arc magmatism in northwest ColombiaThe existence of a tear or STEP fault in the Caribbean Plate, located toward the western end of the Oca‐San Sebastián‐El Pilar Fault System is proposed

Recent modeling shows that surface processes, such as erosion and deposition, may drive the deformation of the Earth's surface, interfering with deeper crustal and mantle signals. To investigate the coupling between the surface and deep process, we designed a three‐dimensional laboratory apparatus, to analyze the role of erosion and sedimentation, triggered by deep mantle instability. The setup is constituted and scaled down to natural gravity field using a thin viscous sheet model, with mantle and lithosphere simulated by Newtonian viscous glucose syrup and silicon putty, respectively. The surface process is simulated assuming a simple erosion law producing the downhill flow of a thin viscous material away from high topography. The deep mantle upwelling is triggered by the rise of a buoyant sphere. The results of these models along with the parametric analysis show how surface processes influence uplift velocity and topography signals. Understanding coupling and feedback between mantle and surface dynamicsNew experimental procedure to scale mantle convection and surface erosionEffect of surface unloading and loading on rock uplift history

Back‐arc basins such as the ones behind the island‐arcs of the Western Pacific Ocean or the ones in the Mediterranean Sea are ubiquitous structures of the Earth. They are extensional basins forming in the overriding plate behind subduction zones and similarly to continental rifts, they can exhibit different structural styles from narrow, localized rifting to wide‐rift extension. While these different structural styles have been long recognized, the factors controlling the style of extension in these basins have not been explored properly. We use thermo‐mechanical models to investigate how the relative rates of progressive build‐up of slab‐pull force and of convective thinning and thermal weakening of the overriding plate control the style of back‐arc rifting. Following subduction‐initiation, a high subducting plate velocity results in rapid build‐up of the slab‐pull force. The relatively low rate of convectively thinning and associated moderate weakening of the overriding plate require slab‐pull to build up to close to its maximum value to overcome the high back‐arc integrated strength resulting in a narrow back‐arc rift. In turn a low subducting plate velocity in comparison with the timescale of convective thinning of the overriding plate allows for significant back‐arc weakening before the slab‐pull force becomes large enough to drive back‐arc extension. In this case, the back‐arc exhibits a wide rifting style as extension occurs at significantly reduced overriding plate integrated strength. Our model results provide an explanation why some subduction zones exhibit wide, distributed extension in the overriding plate such as for instance observed in the Pannonian basin. The relative pace of slab‐pull force build‐up and overriding plate weakening has a crucial role in setting the style of back‐arc riftingOur slowly converging subduction model with narrow oceanic basin and weak back‐arc reproduce first order features of the Pannonian basin The relative pace of slab‐pull force build‐up and overriding plate weakening has a crucial role in setting the style of back‐arc rifting Our slowly converging subduction model with narrow oceanic basin and weak back‐arc reproduce first order features of the Pannonian basin

We use 2.5 to 14 years long position time series from >800 continuous Global Positioning System (GPS) stations to study vertical deformation rates in the Euro‐Mediterranean region. We estimate and remove common mode errors in position time series using a principal component analysis, obtaining a significant gain in the signal‐to‐noise ratio of the displacements data. Following the results of a maximum likelihood estimation analysis, which gives a mean spectral index ~ −0.7, we adopt a power law + white noise stochastic model in estimating the final vertical rates and find 95% of the velocities within ±2 mm/yr, with uncertainties from filtered time series ~40% smaller than from the unfiltered ones. We highlight the presence of statistically significant velocity gradients where the stations density is higher. We find undulations of the vertical velocity field at different spatial scales both in tectonically active regions, like eastern Alps, Apennines, and eastern Mediterranean, and in regions characterized by a low or negligible tectonic activity, like central Iberia and western Alps. A correlation between smooth vertical velocities and topographic features is apparent in many sectors of the study area. Glacial isostatic adjustment and weathering processes do not completely explain the measured rates, and a combination of active tectonics and deep‐seated geodynamic processes must be invoked. Excluding areas where localized processes are likely, or where subduction processes may be active, mantle dynamics is the most likely process, but regional mantle modeling is required for a better understanding. We show a first synoptic view of vertical GPS rates for the Euro‐MediterraneanVertical velocity gradients occur at different spatial scalesCorrelation between vertical velocities and topography is apparent in many areas

The fate of a convergent continental margin is investigated. We perform a set of 2D numerical models to study how and why continental collision can evolve in different scenarios. Since the rheology of continental lithosphere has a major control on the dynamics of subduction, we explore a range of different lithosphere and lower crust viscosity values to understand their sensitivity on the possible scenarios. We find that with a rheologically layered crust both delamination and break‐off are feasible. We identify three modes: (1) slab detachment, in which the lithospheric mantle and the crust are strongly coupled, subduction slows down and the slab eventually breaks; (2) delamination of the lithospheric mantle that separates from the crust and continue to subduct and (3) an intermediate mode where the lithospheric mantle and the crust remain partially coupled, resulting in an initial stage of delamination followed by the slow down and cessation of subduction. Delamination and break‐off are both feasible with a rheologically layered crustA low viscosity lower crust, suitable for young continents, favours delaminationExamples of observed subduction modes are showed for Mediterranean subduction

The East Tenda Shear Zone is the regional structure that marks the Alpine overthrusting of the Ligurian-Piedmontese ocean onto the Variscan Corsica. We present the first report of a Na-pyroxene (acmite)- rutile-bearing assemblage from a phyllonitic shear zone that occurs within the gneissic lithologies of the East Tenda Shear Zone. Acmite hosts inclusions of Na-amphibole and titanite, and is rimmed by retrogressive biotite. Forward modelling of the shear zone assemblages in the NCKFMASTho chemical system indicates a cold burial-exhumation path (palaeogeothermal gradient <10 °C km-1) and a metamorphic climax with minimum pressure of 1.2 GPa and temperatures of 350-400 °C. U-Pb thermal ionization mass spectrometry analyses on synkinematic rutile yield a 3D array with an age of 48 ± 18 Ma (MSWD 7.3), whereas coexisting acmite-phengite and coatings of oxides or sulphides provide an intercept at 54 ± 8 Ma (MSWD = 48). The scatter of the arrays is considered to reflect secondary disturbances of the system and the age provided by acmite-phengite and the coatings at 54 ± 8 Ma is considered the most reliable estimate for shear zone formation. Implications of these new metamorphic and geochronological data are discussed in the regional framework of the Alpine geology and integrated in the plate-tectonic scenario of the central Mediterranean. [ABSTRACT FROM AUTHOR]

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While there has been a lot of work focusing on improving our understanding of divergent and convergent plate boundaries, the intricate nature of back‐arc extension, where subduction and large‐scale extension occur and interact in close, is yet to be explored properly. It has long been proposed that the strength of the subduction interface, which depends among others on the amount of subducted sediments, plays a pivotal role in subduction dynamics. Here, we investigate the role of back‐arc rheology and subduction interface strength on the deformation style of the overriding plate. Using two‐dimensional thermomechanical model experiments, we demonstrate, that the presence of a weak mantle–lithospheric domain in the overriding plate can result in back‐arc breakup even during the subduction of narrow, land‐locked oceanic basins such as those found in the Mediterranean region. The thinning of the back‐arc mantle–lithosphere results in a weaker overriding plate, hence a lower slab‐pull force is sufficient to initiate back‐arc extension. Convective thinning at the subduction interface also reduces the length of the interface, reducing the portion of slab‐pull lost as energy dissipation. A weak plate interface, can also reduce the energy dissipated along the subduction zone, leading to earlier extension. A detailed analysis of the forces shaping the overriding plate stress field shows that transmission of slab‐pull force has a predominant role while viscous basal drag has a negligible effect in our experiments. Our results compare favorably with large‐scale characteristics of land‐locked Mediterranean back‐arc basins such as the North Tyrrhenian basin and the Pannonian basin. Subduction interface strength has important role in back‐arc stress stateBack‐arc extension in 2D is facilitated by weak overriding plate rheologyThe subduction of narrow oceanic domains can generate enough slab‐pull to create back‐arc breakup Subduction interface strength has important role in back‐arc stress state Back‐arc extension in 2D is facilitated by weak overriding plate rheology The subduction of narrow oceanic domains can generate enough slab‐pull to create back‐arc breakup

Relations between normal faults and pre-existing thrust faults are classically described in terms of three basic situations: normal faults can cross-cut thrust faults; they can branch out from thrust faults at depth on a de´collement level, or they can entirely reactivate thrust planes. The mechanical aspects of these types of interaction were studied by analogue modelling in which sand simulates the ‘brittle’ rocks and silicone putty an interlayered de´collement. The models underwent compression, producing thrust faults with variable dips, followed by extension. Three possible ways of interaction are described here: (a)no interaction occurs in the case of low-dip thrust faults (<32 ° ± 1 °) and normal faults are developed independently, displaying a listric geometry; (b)branching at depth on the de´collement level occurs when dip of the thrust faults reaches 32 ° ± 1°. In this case, the dip of the normal faults, whose geometry becomes planar, decreases with increasing thrust dip. We suggest that this change in dip of normal faults depends upon the rotation of stress tensor axes along the pre-existing fault zone, where a drop in the friction coefficient is likely to occur; (c)reactivation occurs in brittle material when dip of the pre-existing fault exceeds 41° ± 1°.

Back‐arc regions are usually punctuated by pulses of tectonic deformation, lasting for few tens of millions of years. Yet, the origin of those short‐lived deformation episodes is disputed. Here, we compile structural, stratigraphic, geochemical, and geochronological data from Iran and we combine them with a kinematic reconstruction to show that the back‐arc region of the Central Neotethys subduction zone was affected by alternating pulses of extension and compression, linked to episodes of trench retreat and advance, respectively. To back‐up these observations and investigate the causes of such a trench behavior, we run 2D numerical models exploring (i) the dynamics of subduction into a viscously stratified mantle, and (ii) the deep slab deformation induced by mineral phase changes at the mantle transition zone. Our results indicate that episodes of trench retreat and trench advance, like those observed in the Central Neotethys domain, emerge spontaneously by slab folding, and penetration into the mantle transition zone. We propose a coupled mantle‐surface tectonic evolution model of the Central Neotethys slab that reconciles back‐arc deformation and short‐lived pulses of upper‐plate vertical motion in a unique, dynamically self‐consistent model of deep mantle subduction. The upper plate of the Neotethys subduction system has been deformed by alternating episodes of compression and extension since the CretaceousThe alternating episodes of deformation are due to the episodes of advancing and retreating trenchNumerical models simulate the episode of trench migration and upper‐plate deformation by slab folding in the mantle transition zone The upper plate of the Neotethys subduction system has been deformed by alternating episodes of compression and extension since the Cretaceous The alternating episodes of deformation are due to the episodes of advancing and retreating trench Numerical models simulate the episode of trench migration and upper‐plate deformation by slab folding in the mantle transition zone

In typical subduction systems, plate convergence is subperpendicular to the trench. The Gibraltar Arc System is exceptional, with its narrow subduction arc oriented N‐S and laterally “squeezed” by the NNW‐SSE tectonic convergence between Nubia and Iberia. The extent to which the slab is still coupled to the surface and how it interacts actively with the surrounding mantle is a matter of ongoing debate. Here, we analyze new densely spaced GPS data, together with crustal and mantle observations, to better understand the slab kinematics, plate dynamics, and mantle flow. In light of previous and current research, we find that subduction below the Gibraltar Arc is currently in the middle of a disruption process, with parts of it already detached and others yet coupled to the surface. In particular, the slab seems to be detached to the north of the Gibraltar Strait, with a small portion still attached to the surface or in the process of detaching below the western Betics. South of Gibraltar, the slab is still coupled to the overriding plate, although the subduction seems to be very slow or stopped. Flow of mantle material around the detached portions of the slab causes most of the surface uplift and a positive residual topography anomaly. Our findings show that the interplay between slab dynamics, mantle flow, and plate convergence explains much of the observed residual topography, surface motion, seismicity, and mantle structure. The Gibraltar subduction is undergoing a phase of progressive lateral disruption, with some segments still attached to the surface in the Rif and western BeticsThe slab appears segmented into two domains, one north and the other south of the Gibraltar strait; the segmentation is likely driven by Eurasia‐Nubia convergenceMantle flow around the slab seems still active and causing most of the surface uplift, although the slab is not retreating anymore

The dynamic topography links with the mantle structures at various temporal and spatial scales. However, it is still unclear how it relates to the dynamics of subducting lithosphere when plates reach the mantle transition zone and lower mantle. Seismic tomography images show how slab morphologies vary from sinking subvertically into the lower mantle, to lying flat above the upper‐lower mantle discontinuity, to thickening in the shallow lower mantle. These slab shapes have been considered to be the result of variable interaction of the slab with the upper‐lower mantle discontinuity at ~670 km depth. Previous studies show that periodic deep slab dynamics can explain a variety of enigmatic geological and geophysical observations such as periodic variations of the plate velocities, trench retreat and advance episodes, and the scattered distribution of slab dip angle in the upper mantle. In this study, we use two‐dimensional subduction models to investigate the surface topography expression and its evolution during slab transition zone interaction. Our models show that topography does not depend on slab morphology; indeed, the dynamic topography cannot distinguish between a slab sinking straight into the lower mantle and slab stagnation at the upper‐lower mantle boundary. However, topographic oscillations are related to episodes of the trench advance and retreat, which in turn are linked to the slab folding behavior at transition zone depths. Our results suggest that the surface transient signal observed by geological studies could help to detect deep subduction dynamics. Our results suggest that surface transient signal can help to detect deep subduction dynamics

The E-W-opening Tyrrhenian Sea developed after the Cretaceous-Palaeogene Alpine collision, nearly perpendicular to the motion of the African plate, as a back-arc of the Adria-Ionian westward subduction. Three driving mechanisms have been proposed to explain the dynamic evolution of the Tyrrhenian-Apennine system: (1) the northward indentation of the African plate; (2) the retreating subduction of the Adria-Ionian lithosphere; and (3) the gravitational collapse of the Alpine post-collisional wedge. In order to define the relative contribution of each of these mechanisms in the Neogene dynamic of the Tyrrhenian-Apennine system, we performed 3-D laboratory experiments, in which we simulated a retreating subduction process in a compressional regime oriented perpendicularly to the direction of subduction; in this framework we also tested the influence of the gravitational collapse of the overriding plate. Experiments were constructed using dry sand and silicone putties to simulate brittle upper crust and ductile lower crust/upper mantle, respectively; these layers floated on a high-density, low-viscosity glucose syrup which simulated the asthenosphere. The main conclusion of our experiments is that large-scale continental extension, similar to that observed in the Tyrrhenian area, could be reproduced perpendicular to the shortening direction induced by the indentation of the African plate; in this framework, extensional processes are indeed possible if the trench retreat velocity is higher than the rate of shortening induced by the advancing African plate. Our experimental results indicate that this high trench retreat velocity could be explained by the coexistence of the gravitational collapse of the post-Alpine wedge with a slab-pull process, linked to the retreating subduction of the Adria-Ionian plate. While the first mechanism is predominant in the Northern Tyrrhenian area, the second one seems to be important in the latest stage of extension and oceanic accretion of the Southern Tyrrhenian area.