Andrea Sembroni

We present the main results of a multidisciplinary study assessing geological, geophysical and geomorphological signals induced by lithosphere and/or deep mantle dynamics on the morphotectonic evolution along a ca. 700 km-long traverse stretching from the Greater Caucasus, across the Lesser Caucasus and eastern Anatolia, into the Arabia-Eurasia suture zone and the northernmost Arabian platform. The results define a complex history punctuated by sequential terrane accretion and incremental deformation culminating in the Arabia-Eurasia collision and the coeval deformation of a wide swath of the European hinterland.The inversion of the prominent positive linear anomalies of the regional gravity field defines discrete crustal density inhomogeneities, which can be interpreted as related to specific tectonic events, thus placing cogent constraints on the accretionary history and the overall anatomy of the eastern Anatolian-Caucasian lithospheric agglomerate. Three linear belts of intracrustal increased density mark the presence of suture zones along (i) the Greater Caucasus, (ii) the Lesser Caucasus, and (iii) a previously unidentified parallel belt ca. 80 km south of the Lesser Caucasus. The latter gravity anomaly delineates the southwestern margin of the South Armenian Block, a lithospheric element (microplate) whose existence has long been a matter of debate.In the Caucasian domain intraplate deformation was triggered by far-field propagation of plate-margin collisional stress which focused preferentially along rheologically weak zones such as the Greater Caucasus and the adjacent Adjara-Trialeti fold-and-thrust belt of Georgia, two intraplate orogens produced by structural inversion of parallel continental rift zones located on the Eurasian plate. The integration of multiple thermochronometric techniques and peak-temperature determinations shows that structural inversion was punctuated by two incremental steps starting in the Late Cretaceous and the mid-Miocene. The two episodes of intraplate structural inversion, exhumation, and sediment generation are chronologically and physically correlated with the docking of (i) the South Armenian microplate and the Anatolide-Tauride-Armenian terrane (Late Cretaceous - Paleocene) and (ii) Arabia (Miocene hard collision) against the southern Eurasian plate margin.As to the Lesser Caucasus of Armenia and Azerbaijan, the thermochronologic record of the Late Cretaceous cooling/exhumation event is still present only in a relatively small area of the upper plate of the Amasia-Sevan-Akera (ASA) suture zone where later exhumation has been thermochronologically insignificant. More commonly, rapid cooling/exhumation, which occurred in the Early-Middle Miocene in both the lower and upper plates of the ASA suture zone, has overprinted and obscured previous thermochronologic signatures. Miocene contractional reactivation of the ASA suture zone occurred contemporaneously with the main phase of shortening and exhumation along the Bitlis suture zone marking the Arabia-Eurasia hard collision.The elevation of marine deposits across the eastern Anatolian Plateau indicates a post-collisional surface uplift of ∼2,000 m. This uplift occurred in two steps: (i) at 10–11 Ma with the opening of a slab window and the concomitant arrival of a mantle flow from Arabia, both processes supporting dynamically the topography, and (ii) at ∼5 Ma with the continued inflow coupled with the isostatic response to the ongoing crustal shortening.

Magmatism is an important driver of topographic change. However, our understanding of its long-term impact on topographic evolution remains incomplete. In the framework of the MIGRATE project, we investigate the potential surface response to magmatic intrusions in the active Larderello-Travale geothermal field, in the northern Italian Apennines. Here, multiple igneous bodies have intruded since the late Pliocene causing at least 500 meters of large-wavelength surface uplift. We combine available stratigraphic information with a new set of morphological analyses and river inversion models to quantify, the magnitude, rate, and spatial distribution of surface uplift throughout over the last 3.5 Ma. In describing the style of the uplift, we report a temporal and spatial correlation between rock uplift pulses and middle crust magma injections. For the first time in this area, we document the positive feedback between different magma injections and local surface responses (e.g. river incision). We use a surface evolution model to suggest a potential scenario of magma emplacement over time. In this sense, we suggest that at the very beginning, uplift rates were higher to the north of the current thermal anomaly, and only over the last 2 Ma the uplift migrated further south. This could indicate that the deep source of the Larderello-Travale geothermal field might not be precisely located underneath the current thermal anomaly. This would allow undocumented plutons (deep enough such that they are not evidenced by shallow thermal anomalies) to be tracked, leading to more conscious and effective strategies for geothermal exploration.

Plate tectonics and mantle dynamics drove the continental collision and topographic evolution in the Eastern Mediterranean – Tethyan realm leading to the closure of the Tethys Seaway, which once linked the Atlantic and Indo-Pacific oceans. The closure led to reorganizations in ocean circulation, diversification and migration of marine and terrestrial species, and climatic changes. In this Review, we evaluate the causes and consequences of closing the Tethys Seaway and quantify the processes generating topography in this region for the last 66 million years. We discuss how the arrival of the Afar Plume and northward mantle flow influenced dynamic topography and caused regional uplift and volcanic activity. Mantle convection ultimately established a permanent land bridge between Africa and Asia in the Miocene, enabling one of the greatest faunal interchanges of the Cenozoic.

The East Africa - Arabia topographic swell is an anomalously high-elevation region of ~4000 km long (from southern Ethiopia to Jordan) and ~1500 km wide (from Egypt to Saudi Arabia) extent. The swell is dissected by the Main Ethiopian, Red Sea, and Gulf of Aden rifts, and characterized by widespread basaltic volcanic deposits emplaced from the Eocene to the present. Although most agree that mantle plumes play a role in generating the swell, several issues including the number and locations of plumes and the uplift signatures remain debated. We seek to address these questions and provide a general evolutionary model of the region. To this end, we conduct a quantitative analysis of topography to infer isostatic and dynamic contributions. When interpreted jointly with geological data including volcanic deposits, the constraints imply causation by a single process which shaped the past and present topography of the study area: the upwelling of the Afar superplume. Once hot mantle material reached the base of the lithosphere below the Horn of Africa during the Late Eocene, the plume flowed laterally toward the Levant area guided by pre-existing discontinuities in the Early Miocene. Plume material reached the Anatolian Plateau in the Late Miocene after slab break-off and the consequent formation of a slab window. During plume material advance, buoyancy forces led to the formation of the topographic swell and tilting of the Arabia Peninsula. The persistence of mantle support beneath the study area for tens of million years also affected the formation and evolution of the Nile and Euphrates-Tigris fluvial networks. Subsequently, surface processes, tectonics, and volcanism partly modified the initial topography and shaped the present-day landscape.

Landslides are among the most dangerous natural hazards impacting on human life claiming lives and affecting economy and society. For this reason, the cost of the repeated occurrence of landslides could become unsustainable for a country. In this respect, the assessment of the susceptibility to landslide of a region becomes crucial to mitigate the economic and societal implications and to save lives. A typical approach starts from the inventory of landslides by field survey coupled with database consulting. This activity could assess the discriminating and predisposing factors, defining the weight of each of them on the slope stability. Overlaying resulting maps in GIS environment, a susceptibility map of each type of landslide could be produced. At local scale, the field survey allows to identify properly the past events and the factors that contributed to the instability. Unfortunately, sometimes managers and policy makers ask for landslide prediction regarding areas that are too large for a detailed field survey. As a consequence it is necessary to work out methods that start from available database. The main problem is to check the quality of the data and to eliminate possible errors. Starting from a classical susceptibility analysis based on landslide inventory derived from filed survey, we propose a modified method applicable to database on regional scale area. In detail, we check the quality of the database with respect to landslide locations eliminating unproper sites according to hillslope interval or rock-type, i.e. the two main discriminating factors. Our results show how this kind of approach allows to produce maps that are useful for general landscape management indicating the areas susceptible to each type of landslide. These preliminary maps are the basis for identifying the areas where more detailed studies are needed.

Post-subduction tectonics can involve a wide range of spatiotemporal processes associated with regional and large-scale upper mantle forces. To better understand the interaction between these forces in collisional settings, we focus on active mantle dynamics beneath the East Anatolian Plateau, a well-documented segment of the Arabian-Eurasian continental collision zone. In detail, we use state-of-the-art instantaneous thermomechanical models by combining the advantages of 3D numerical modeling with high-resolution imaging techniques. We analyze the model’s outputs, such as 3D stress-strain and temperature variations of upper mantle convection and reconcile them with numerous geological and geophysical observations. Our results show prominent northward-directed channel flow in the mantle that cuts across the plateau and surroundings, from the Arabian foreland to the Greater Caucasus domain. This result reproduces and elucidates the proposed ~SW-NE-oriented Anatolian Background Splitting pattern and recent seismic low-ultra low-velocity anomalies. We argue that this large-scale upper mantle flow constitutes the engine for the long-wavelength dynamic topography (~400 m) in the region and promotes the relatively small-scale convection pattern by supporting intraplate rift tectonics in the extensional Van Lake zone.

The spatiotemporal interaction of large‐ and regional‐scale upper mantle forces can prevail in collisional settings. To better understand the role of these forces on post‐subduction tectonics, we focus on mantle dynamics in the East Anatolian Plateau, a well‐documented segment of the Arabian‐Eurasian continental collision zone. Specifically, we analyze multiple forces in the upper mantle, which have not been considered in previous studies in this region. To this end, we use a state‐of‐the‐art 3D instantaneous geodynamic model to quantify the dynamics of thermally defined upper mantle structures derived from seismic tomography data. Results reveal a prominent SW‐NE‐oriented mantle flow from the Arabian foreland to the Greater Caucasus–a plumelet–through a lithospheric channel under the East Anatolian Plateau. This plumelet induces localized dynamic topography (∼500 m) around the extensional Lake Van province, favoring NE‐directed compression and westward escape of the Anatolian plate. We suggest that the Lake Van region is an active magma‐rich intraplate rift in the Africa‐Arabia‐Anatolian plume‐rift system. The rift zone was probably initiated by Neotethyan subduction‐related forces and has been reactivated and/or sustained by the plumelet‐induced convective support. Our findings are consistent with numerous observations, including the recent low‐ultralow seismic velocities with a SW‐NE splitting anisotropy pattern, geochemical and petrological studies, and local kinematics showing upper mantle‐induced extensional tectonics in the collisional region.

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.