The Mediterranean domain has been and continues to be a test bed for new imaging and geodynamic modelling techniques. While significant progress has been made in understanding the tectonic processes in the region, important questions regarding the driving forces, the three-dimensional lithospheric stress field, seismic coupling, and magma ascent remain unanswered. The integration of 3D geophysical imaging with geologic observations and modelling allows us to bridge spatial and temporal scales, providing an overview of the entire crust-mantle system.
In this session, we intend to create an interdisciplinary platform to present recent results and new concepts, as well as to highlight open questions and methodological challenges. Our focus will be on the evolution of Mediterranean tectonics and geodynamics, covering a time span from the Permian to the present.
We invite contributions from all disciplines and scales in the earth sciences including, but not limited to, field geology, geochemistry, petrochronology, volcanology, geophysical methods, geodesy, seismology, sedimentology, geodynamic modeling, and marine geology.
Tunisia occupies a critical position at the eastern termination of the Atlas system, within the central Mediterranean plate boundary zone. The oblique convergence between the Nubian and Eurasian plates is here accommodated by a network of strike-slip and thrust faults that characterize transpressio tectonics. Moderate but persistent seismicity marks the occurrence of destructive historical earthquakes (Utique 408 AD, Kairouan 859 AD) and damaging instrumental events such as Metlaoui 2023 (Mw 5) and Meknassy 2025 (Mw 4.8) underscoring the need to quantify present-day deformation for seismic hazard assessment.
To address this need, the collaborative ONM-ITES project has built a multi-scale GNSS network. It integrates data from 21 stations of the OTC (Office de Topographie et Cadastre) network with 6 days of record per year from 2012 to 2019, an expanded national campaign grid of 24 TU stations (with 3 days of record per campaign 2019, 2021, 2023 and 2025), five new permanent stations strategically installed since June 2023, and two dense temporary networks of 16 stations each on the Gafsa-Metlaoui (TG) and Kairouan (TK) fault zones (with 3 days of record per campaign each year from 2021 to 2025) totaling 82 GNSS stations with known precise velocities in Tunisia. Processing is done in ITRF2020 with respect to a fixed Eurasia reference frame yields a robust horizontal velocity field.
Our velocity field reveals a non-linear south-to-north decreasing gradient, with rates ranging from 5.8 mm/yr in the south to as low as 0.8 mm/yr in the far north. This pattern reflects the partitioning of Nubia-Eurasia convergence across Tunisia's distinct tectonic domains. The derived strain rate field shows a striking spatial correlation between areas of high strain concentration and zones of intense historical and instrumental seismicity. The strain pattern provides independent validation and precise location of major deformation boundaries.
Building on this, we present a first order block model developed to interpret the observed velocity field and active tectonics. This model delineates the main tectonic blocks and strain distribution of Tunisia based on residual velocity analysis and quantifies the slip rates along their bounding faults. It provides the first geodetically-derived estimates of long-term slip rates in agreement with key seismogenic fault systems in Tunisia.
This integrated analysis synthesizes the geodetic deformation and related seismic cycle from the derived slip rates and localized strain concentrations. It provides critical constraints to assess the seismic potential and seismic hazard evaluation in Tunisia.
How to cite: Kristou, H., Masson, F., Bahrouni, N., Meghraoui, M., and Ulrich, P.: GNSS velocities and kenematic block model in Tunisia : quantifying present-day active deformation along the Africa-Eurasia plate boundary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17352, https://doi.org/10.5194/egusphere-egu26-17352, 2026.
The Gibraltar Arc, comprising a northern branch in southern Spain and a southern limb in northern Africa separated by the back-arc Alboran Sea basin, is a key sector of the plate boundary between Africa and Eurasia, which represents the most tectonically active region of the western Mediterranean. In this region, plate convergence is accommodated through a complex pattern of deformation involving compressional and extensional regimes. In the central Betic Cordillera, deformation is dominated by WSW-directed extension and normal faulting, producing moderate seismicity in the Granada basin. In contrast, NNW–SSE compression prevails in the northern Alboran Sea. The interaction and mechanical coupling between these contrasting deformation styles occur across a structurally complex zone defined by two major antiforms, the Sierra Nevada to the north and the coastal Sierra de Lújar–Contraviesa–Gádor to the south, separated by a synformal domain, whose roles in stress transfer and seismicity remain poorly understood. Seismicity propagates onshore northward from the marine faults, yet no major surface structures have been identified on land that could account for this activity. To the west, significant seismicity is absent until reaching the southernmost normal faults of the Granada Basin, located approximately 50 km away. In this sector, the Padul fault accommodates most of the WSW extension, characterized by a significant creep component.
In this study, magnetic data have been collected along several N-S profiles, revealing a prominent regional E-W elongated dipole, consistent with existing aeromagnetic data. Moreover, a well-defined N-S dipole suggests the existence of a shallower conductive body. Preliminary processing and modelling of long-period magnetoteluric data from a dense survey of 20 sites further indicate the existence of conductive bodies at multiple crustal depths. Incipient field reconnaissance identifies widely spread NW-SE trending joints affecting marble lithologies, consistent with dominant regional extension NE-SW. Peridotite bodies crop out in the central-western Betic Cordillera, suggesting that similar lithologies and their associated high conductivity may also be present in depth in the study area. Our results point to the existence of a hidden crustal structure, expressed as conductive anomalies at different crustal levels, which localize brittle deformation and act as a mechanical link between these contrasting deformation styles. This hidden structure plays a key role in focusing deformation and controlling the propagation of seismicity onshore, despite the absence of major mapped surface faults, with important implications for seismic hazard assessment in the region.
Acknowledgements
This publication is part of the PID2022-136678NB-I00 project, funded by Spanish Ministry of Science, Innovation and Universities/State Research Agency MICIU/AEI (10.13039/501100011033) and by the European Regional Development Fund (ERDF), EU. In addition, the author V.M.B. gratefully acknowledges the pre-doctoral fellowship associated with grant PREP2022-000591, financed by MICIU/AEI (10.13039/501100011033) and by the European Social Fund (ESF+).
How to cite: Mora-Bajén, V., Galindo-Zaldívar, J., Ercilla, G., Baena-Ortola, S., and González-Castillo, L.: Unveiling the crustal structure of the central-eastern Betic Cordillera, Southern Spain: a potential geological hazard?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13747, https://doi.org/10.5194/egusphere-egu26-13747, 2026.
The Western Mediterranean is constituted by a series of back-arc basins that opened in response to the African slab rollback throughout the Alpine orogenies. The Ligurian Basin occupies the northeastern termination of this realm and resulted from the rifting and subsequent drift of the Corsica-Sardinia block, between Oligocene and Burdigalian-Langhian times, coevally with the neighbouring Western Alpine collision. The nature of its basement, beneath thick sedimentary deposits, has long remained elusive. The SEFASILS cruise acquired deep penetrating wide angle seismic data from densely deployed ocean bottom sensors, as well as long offset reflection and gravity data. The obtained tomographic images unequivocally reveal a large expanse of exhumed mantle flooring the northern half of the basin beneath basinal deposits. Further south, intermediate crustal velocities are found and the nature of the basement is more ambiguous. Using satellite-derived gravity measurements and taking into account the documented kinematics of the main phase of the Ligurian opening, we show that most of the seafloor—if not all—is indeed of oceanic origin and that the observed mantle tract was emplaced from an accretion centre inside the basin rather than from under the flanking margin. In particular, the extinct spreading axis is revealed by free-air gravity anomalies. These results thus show that, albeit significant opening rates of ~4 cm/yr or more are inferred here, seafloor spreading consisted essentially in mantle unroofing with little to no melt production. Moreover, a domain of ultrathinned continental crust is also evidenced at the toe of the northern margin, that is evocative of some ductile-dominant deformation immediately prior to breakup. Mantle exhumation seems to have occurred successively and somewhat continuously throughout the basin formation on opposite-verging continental and oceanic detachment systems, active prior to and after breakup respectively.
How to cite: Dessa, J.-X., Chamot-Rooke, N., Canva, A., Delescluse, M., Alessandra, R., Marie-Odile, B., Laure, S., Riccardo, A., Isabelle, T., and Cédric, B.: The opening of the Ligurian Sea seen through combined deep seismic, gravity and kinematic analyses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12040, https://doi.org/10.5194/egusphere-egu26-12040, 2026.
The Alpine–Apennine–Dinaric system records the complex interaction between continental collision, subduction, slab rollback, and lithospheric deformation involving the Eurasian and Adriatic plates. While isotropic seismic velocity models have significantly advanced our understanding of Alpine deep structure, they often fail to uniquely resolve deformation styles, slab geometry, and crust–mantle coupling. Here we use seismic radial anisotropy as a tool to investigate how deformation is distributed from the upper crust to the upper mantle across the Alpine collision zone.
Using the AlpRA25 model, a new high-resolution 3-D shear-wave velocity and radial anisotropy model derived from joint inversion of Rayleigh and Love surface waves, we image systematic variations in the radial anisotropy parameter ξ = Vsh²/Vsv² from 5 to 250 km depth. The AlpRA25 model reveals spatially coherent variations in radial anisotropy that correlate with major tectonic features and deformation domains.
In the upper crust, negative radial anisotropy (ξ < 1) spatially correlates with major fold-and-thrust belts, steeply dipping fault systems, and the Eurasian–Adriatic plate interface, indicating the dominance of subvertical fabrics produced by shortening and tectonic stacking. Similar signatures are observed in regions of extended or oceanic crust in the western Mediterranean, consistent with steep faults and dyke intrusions formed during rifting and back-arc extension. In the Northern Apennines, radial anisotropy in the upper crust reflects the overprint by extensional structures in the Tyrrhenian domain (ξ > 1), and the compressive tectonic structures in the Adriatic domain (ξ < 1).
The lower crust beneath much of the Alps and Northern Apennines is characterized by strong positive radial anisotropy (ξ > 1) likely of Eurasian origin, indicating pervasive subhorizontal fabrics and ductile deformation, consistent with lower-crustal flow and, locally, with crustal thickening related to delamination.
In the upper mantle, pronounced negative radial anisotropy is imaged within the subvertical segments of recent Eurasian and Apenninic slabs, consistent with vertically oriented olivine fabrics produced by slab descent. Surrounding mantle domains including the western Alps, are dominated by positive radial anisotropy.
Overall, radial anisotropy provides independent constraints on deformation geometry, slab dynamics, and crust–mantle coupling in the Alpine region, demonstrating that anisotropy is essential for discriminating between competing geodynamic models of continental collision that cannot be resolved using isotropic velocities alone.
How to cite: Berger Roisenberg, H., Eckel, F., El-Sharkawy, A., Rosenberg, C., Boschi, L., Meier, T., and Cammarano, F.: What does radial anisotropy tell us about the Alpine collision?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4097, https://doi.org/10.5194/egusphere-egu26-4097, 2026.
The Central Mediterranean region is characterized by a wide diversity of geodynamic processes in the context of the long-term plate convergence between Africa and Eurasia during the entire Alpine Cycle. The Adria microplate, deformed amid the two major converging plates of Africa and Eurasia, results in a key piece for the reconstruction of this complex tectonic region. Adria is surrounded by highly deformed converging margins involving three plate subductions with different polarity and with Adria acting as both upper plate in the Alps and lower plate in the Apennines and Dinarides. One of the striking aspects of these subducted/delaminated slabs is their conspicuous segmentation at depth, as observed in tomographic studies, separated by lithospheric gaps that have been commonly interpreted as occurring during the subduction processes. Moreover, the NW-dipping Ionian subduction under the Calabrian Arc seems to be connected with the SE termination of the slab beneath the Apennines. Unveiling the lithospheric structure of the Calabrian subduction zone, one of the narrowest arcs on Earth, is crucial for understanding the geodynamic evolution of the Mediterranean and adjacent marginal seas.
In this presentation, we will show our findings of a geophysical-geochemical model of the lithosphere and uppermost sublithospheric mantle of the Adria microplate and its surroundings. We will present the lithospheric structure of the Adria microplate and the two opposing mantle slabs along its NE and SW margins. The modeling shows the presence of two asthenospheric mantle wedges aligning with the Apennine and Dinaride continental mantle slab rollback, along with cold sublithospheric anomalies beneath the NE and SW margins of Adria. The structure of the northern Adria region, is consistent with the northeastward rollback of the SW Adriatic slab (beneath Northern Apennines), leading to subsequent delamination of the continental mantle. In the southern Adria region (southern Apennines), the complex deep structure results from the variably oriented lithospheric slabs, and nearly 90-degree shift of the tectonic grain between the southern Apennines and the Calabrian Arc. At the SW Adria margin, beneath the northern Apennines, we interpret the subducting slab attached to the shallower lithosphere, while a slab gap is modeled in the southern Apennines. Our studies suggest that they may represent inherited segments of the Mesozoic Adria plate margins. Underneath the Ionian Sea, our results show a thick crust and a relatively deep Lithosphere-Asthenosphere Boundary (LAB), contrasting with the thinner magmatic crust and lithospheric mantle of the Tyrrhenian Basin. The sharp change in lithosphere thickness, from the Calabrian accretionary wedge to the Tyrrhenian back-arc basin, contrasts with the greater lithosphere thickening below the subduction zone. Our results confirm the presence of an attached Ionian slab beneath the Calabrian Arc. The slab is colder and denser than the surrounding mantle and has a more fertile composition than the lithospheric mantle of the Southern Tyrrhenian.
This research is funded by the GEOADRIA (PID2022-139943NB-I00) project from the Spanish Government
How to cite: Jiménez Munt, I., Verges, J., Zhang, W., Negredo, A. M., Najafi, M., Gómez-García, A. M., García-Castellanos, D., Viaplana-Muzas, M., Ortega-Gelabert, O., Cruset, D., and Torné, M.: The lithosphere and upper mantle of Adria microplate from integrated geophysical-geochemical and geodynamic modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13720, https://doi.org/10.5194/egusphere-egu26-13720, 2026.
As one of Europe’s most active volcanoes, Mount Etna poses a significant geohazard, with recurrent eruptive activity directly affecting a population of over a million in eastern Sicily. Accordingly, Mount Etna has been the in the focus of enduring scientific research concerning the relation of the volcano to the subduction of the Ionian Sea beneath the Calabrian Arc. Contrary to its famous neighbors in the Aeolian archipelago like Stromboli or Vulcano, Mount Etna is not a back-arc volcano. However, during the Holocene its overall intraplate-type geochemical composition has increasingly been influenced by subduction-related magma geochemistry. Its location and compositional anomalies have been explained with asthenospheric flows at the Ionian slab edge, slab windows in the region or oceanic slab brake-offs beneath Sicily.
This research is based on a combined inversion of ambient noise and earthquake-derived data to develop a comprehensive 3D shear-wave velocity model for the broader southern Central Mediterranean resolving the crust and upper mantle. The inversion utilizes an extensive dataset comprising 95,000 Rayleigh wave phase velocity dispersion curves and 40,000 Love wave curves from ambient noise and teleseismic earthquake measurements. Azimuthally anisotropic phase velocity maps were generated using a regularized least-squares approach and then inverted for depth using a stochastic inversion.
The resulting radially anisotropic 3D velocity model reveals a segment of delaminated but still attached African continental mantle lithosphere beneath Western and Central Sicily. A vertical tear beneath Mount Etna separates the delaminated lithosphere from the Ionian slab in the East. These two lithospheric units form a funnel allowing asthenospheric mantle to flow towards the crust beneath Mount Etna, picking up the subduction related contamination of its geochemical composition on its way. Where the mantle flow connects to the crust, we can evidence – together with local seismicity – the crustal pathways of magmatic fluids fueling Mount Etna. Our model not only explains the particular geochemical signature of Mount Etna but also relevant tectonic processes in the crust as surface expressions of the delamination and tearing processes like deep-seated thrusting in Central Sicily or observed uplift in northern Sicily.
How to cite: Eckel, F., El-Sharkawy, A., Scarfì, L., Barberi, G., Barreca, G., Langer, H., Hansteen, T., Lebedev, S., and Meier, T.: Delamination of Continental Mantle Lithosphere driving volcanism at Mount Etna, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14050, https://doi.org/10.5194/egusphere-egu26-14050, 2026.
The Mediterranean constitutes a complex plate boundary between converging continental plates marked by a wide range of deformation mechanisms, the presence of multiple micro-blocks, and extensional and compressional tectonics. While seismicity and surface kinematics from geodesy highlight (onshore) active plate boundaries and faults, we mostly rely on bathymetry to identify offshore tectonic segmentation. In this work, we explore the potential of automatic detection of maximum gravity gradients to complement our existing seismotectonic databases.
We present a holistic examination of the Mediterranean that integrates gravity, seismology and geodesy to localize weak zones and how they align with the current seismicity and highly-strained areas. We first extracted linear geological features and calculated the Moho depth from Bouguer and free-air anomaly gravity data through gradient computations and minimum-structure inversion modelling, respectively. Then, we synthesized published seismic catalogs, focal mechanisms and surface deformation rates to qualitatively assess the state of crustal stress/strain. We also included a quantitative approach that makes use of clustering. Areas bounded by large-scale gravitational lineaments that agree with large-scale faults and potential kinematic boundaries were classified as tectonic units.
Seismicity, geodesy and delineated maximum gravity gradients agree – to first order – well in highlighting the tectonic boundaries in the region. The maximum gravity gradients showed high potential in accentuating some overprinted/inherited geological structures in the eastern Mediterranean and particularly identified the fault system separating the West Anatolian Graben System and the Cyprian unit, the Aksu-Dinar fault system, which was found to extend to Samsun, Northern Türkiye. We also reproduce the full stretch of the South Levantine Sea fault system whose western end only was previously identified as the North Cyrenaica fault system. While more prominent in Northern Türkiye, the North Anatolian Fault zone was found to extend from Kermanshah, Iran to Vasilevo, Macedonia, covering about 2473 km.
This project has received funding from the European Union's Horizon Europe research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 101180812.
How to cite: Balogun, O. B., Agius, M., Metzger, S., and D'Amico, S.: Combining automatic detection of maximum gravity gradients with seismology and geodetic data to illuminate the crustal architecture of the Mediterranean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18953, https://doi.org/10.5194/egusphere-egu26-18953, 2026.
The Main Marmara Fault - a segment of the active North Anatolian Fault Zone - poses significant seismic hazard to the metropolitan area of Istanbul, where a potentially hazardous earthquake of M>7 is overdue. This part of the larger strike slip system extends across the northern Sea of Marmara and exhibits a still poorly understood segmentation along‐strike, with creeping and locked parts. Continuous research in the recent years using data collected in the GONAF observatory initiated by the ICDP and results obtained in the frame of the DFG-ICDP priority program enabled the construction of a new 3D lithospheric‐scale model of the Sea of Marmara. We combined gravity modelling and seismic tomography analysis with thermal and rheological modelling to derive the crustal density structure to gain insights into the temperature and density configuration of the uppermost mantle, and the geometry of the 1330°C isotherm. We find a lower‐density crust over the western and creeping part of the Main Marmara Fault, and a denser crust below the locked part of the Main Marmara Fault at the Istanbul Zone and analyse and discuss the implications of these structural heterogeneities.
How to cite: Scheck-Wenderoth, L., Fernandez, N., Cacace, M., and Rodriguez Piceda, C.: Thermal and rheological characteristics of the Main Marmara Fault - a segment of the North Anatolian Fault - and its surrounding regions in the Eastern Mediterranean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6464, https://doi.org/10.5194/egusphere-egu26-6464, 2026.
The Eastern Mediterranean marks a region of ongoing ocean closure, starting when Arabia collided with Eurasia around Eocene-Oligocene time, but the modern tectonic configuration has only been established since ca. 4 to 5 Ma. To identify the main drivers of this tectonic evolution and explain delays between apparent drivers and responses, we review evidence for how crustal deformation, surface elevations, and volcanism in the upper plate spanning the Dinarides-Hellenides to Eastern Anatolia evolved in the context of plate reconstructions. We also use geophysical observations to guide a reconstruction of the modern slab geometries and the positions of oceanic-continental lithosphere transitions within the slabs. We then infer how the slabs evolved through time in three dimensions, using the plate reconstructions and geologic history as guides for changes in slab geometry. From this review, we reconstruct a series of paleographic maps (15, 9, and 5 Ma) and cartoons illustrating the 3D geometry of slabs at the same time frames.
Following break-off of the Bitlis slab at least 20 million years ago, the next major event in establishing the modern tectonic regime was the acceleration of Hellenic Trench retreat around 15 Ma, likely associated with the initiation of a trench-orthogonal tear along the east side of the Aegean slab. We show that initiation of the tear could relate to entrance of the Ionian oceanic lithosphere into the subduction zone, as well as the presence of Pindos oceanic lithosphere at greater depths within the slab. The trench-orthogonal tear in turn induced accelerated Hellenic Trench retreat, faster extension in the Aegean, and the start of a “proto-escape” phase of Anatolia. At 5 to 4 Ma, segmentation of the slab beneath the Kefalonia Transfer Fault Zone and further acceleration in Hellenic Trench retreat likely facilitated the localization of the North Anatolian Fault western Turkey, the formation of the East Anatolian Fault, and independent motion of the Adria plate, establishing the modern tectonic regime. Our reconstructions highlight the role of slab dynamics in driving not only the long-term, progressive tectonic evolution of the region, but also sudden plate reconfigurations.
How to cite: Schildgen, T., Faccenna, C., Jolivet, L., Ballato, P., Şengül, E., Yıldırım, C., and Cosentino, D.: Slab Evolution in the Early Pliocene Establishment of the Modern Tectonic Regime in the Adria-Aegean-Anatolian Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11321, https://doi.org/10.5194/egusphere-egu26-11321, 2026.
Accurate understanding of the tectonic architecture from early in the evolution of orogenic belts is important for charting how they amplify into modern-day structures. However, this understanding is hampered by this subsequent deformation. But, as collision mountain belts generally initiate underwater, early synorogenic turbidite systems can reveal this architecture as represented not only by the connectivity and relative bathymetry ahead and across orogens but also by detecting deformation ahead of the main orogenic “front”. This presentation shows how sand fairway mapping is a key, but under-used, tool for understanding basin configuration in evolving convergent plate boundaries. It is underpinned by a simple statement: turbidity currents go downhill. Arguably the most useful are turbidite systems developed early in the evolution of orogenic belts where sand, derived external to the orogen, is flushed across substrates largely comprising pre-orogenic limestones and basinal marls and clays. This allows detection of potential contamination by entrained substrate particles and hence justify long-range correlations along fairways that are subsequently deformed during progressive orogenesis. Modern research has shown that turbidity currents, when confined by seafloor bathymetry, can run out for hundreds of km along rather low bathymetric gradients. The application of modern depositional understanding of confined turbidites provides a diagnostic suite of observations and facies associations to test correlations and detect active basin-floor deformation structures. Two examples are discussed from circum-Mediterranean orogens – the Numidian (early Miocene) of the Maghreb-Apennine orogen and the Annot-Champsaur (early Oligocene) of the Western Alps.
The Numidian sand fairway, derived from North Africa, extends for over 300 km in the central Mediterranean into modern-day central Italy. Turbidites deposited along confined sinuous corridors created by active submarine thrusting. Palaeobathymetry across the submarine thrust belt increased northwards into the future Apennines. The sands overlying various substrate facies, from deep-water clays to platform carbonates – indicating the designations of Mesozoic blocks and basins are unreliable guide for subsequent intra-Mediterranean palaeogeography. It is the down-system palaeobathymetry that benchmarks the water-depth back up-system. The composite Apennine–Calabrian–Maghrebian orogen with its submarine thrust belt had occluded deep-water Tethyan connections through the central Mediterranean by early Miocene times.
The Annot system can be mapped northwards from its source (Corsica-Maures-Esterel) around the Alpine arc, along what is generally interpreted to be a foredeep ahead of the orogen. However, the turbidites are confined by active basin-floor structures, indicating their setting as thrust-top. Both the Ecrins and Argentera basement massifs were over-flowed by Annot turbidites. They are indicative of active crustal shortening partitioned ahead of the main orogen while other tracts of European continental crust were being subducted. This challenges conventional over-simplified descriptions of orogens as “foreland-migrating” and the use of transgressive unconformities in charting this migration.
Although both case-studies are classically-described orogenic “flysch” systems, their deformed segments now caught up in the orogens have, until now, been under-represented. These studies illustrate the utility of turbidite sedimentology, especially reconstructing sand fairways, in building the palaeogeographical reconstructions necessary to characterise the complex, early tectonic regimes of Mediterranean orogens. The results challenge convention.
How to cite: Butler, R.: Early orogenic turbidite systems as tectonic tracers – examples from circum-Mediterranean orogens , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3521, https://doi.org/10.5194/egusphere-egu26-3521, 2026.
The eastern Provence in southeastern France comprises a complex fold-thrust system developed in a Mesozoic sedimentary cover detached above ductile Triassic evaporitic-carbonate levels. The timing of deformation is difficult to constrain due to the absence of syntectonic sedimentary strata. In this study, we investigate the Cannet-des-Maures structure, a key example of the eastern Provence fold-thrust belt, by integrating a balanced, sequentially restored cross-section with U-Pb calcite dating to reconstruct its structural evolution and quantify the time-dependent vertical partitioning of shortening. The present-day geometry of the structure is characterized by a large-scale NE-verging overturned anticline, with second-order SW-verging thrusts developed in its forelimb, that were subsequently tilted and sheared by anticline growth. This architecture reflects limited frontal propagation and strong internal strain localization, kinematically linked to the presence of Triassic evaporitic-carbonate layers in the core of the structure. Theses ductile units acted as décollement levels promoting vertical partitioning of the shortening (from 0.14 to 2.7km) and disharmonic folding between the basement and the overlying Jurassic cover. Structural restoration reveals that the current geometry results from the inversion of an inherited Jurassic rollover structure initially shaped by listric normal fault rooted in Triassic evaporitic-carbonate layers. The basement displays a reactivated, south-dipping extensional fault, which originally controlled the development of the rollover geometry. U-Pb ages of syn-kinematic calcite range from 94 to 4 Ma, providing a robust temporal framework linking Cretaceous extension to Provençal and Alpine compressions. These absolute ages validate the structural interpretation of inverted extensional geometries and demonstrate a long-lived deformation from Provençal to Alpine tectonic regimes. Based on these deformation ages, we propose a five-stage kinematic model identified through sequential restoration between the Late Cenomanian to the Eocene. This reconstruction highlights that the highest shortening rate occurred during the Eocene. Kinematic relationships reveal a combination of thin- and thick-skinned tectonic styles during the Provençal orogeny, later overprinted by reactivation of the Triassic décollement levels during the Alpine phase. By integrating absolute geochronology with structural restoration, this study refines the timing and mechanical understanding of tectonic inversion processes and emphasizes the long-term control of inherited basement structures and ductile Triassic units. The results further indicate southwestward propagation of Alpine deformation into the European foreland, expressed in Provence as a far-field Alpine overprint.
How to cite: Mskine, M. A., Espurt, N., beccaletto, L., Marçot, N., Matonti, C., Guihou, A., Deschamps, P., Lahfid, A., and Parizot, O.: Sequential restoration of a thrust system constrained by cross-section balancing and U-Pb calcite dating: the Cannet-des-Maures structure, Eastern Provence, France, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9565, https://doi.org/10.5194/egusphere-egu26-9565, 2026.
The structural and thermal architecture of the Ligurian Flysch Nappes in the southwestern Alps remains poorly constrained, despite their key role in late Alpine wedge construction. Reconstructing their burial history and kinematic evolution requires an integrated approach combining structural geometry, independent thermal constraints, and physically consistent numerical modeling. Here, we couple balanced and restored geological cross-sections with Raman Spectroscopy of Carbonaceous Material (RSCM) thermometry to tightly constrain 1D thermo-kinematic modeling of nappe emplacement. Three NE-SW-trending balanced cross-sections (30 to 46.5 km long) were constructed across the para-autochthonous Subalpine foreland, the four main Ligurian Flysch Nappes (Sanremo, Moglio-Testico, Borghetto-Colla Domenica, and Albenga), and the internal Briançonnais domain. Structural restorations provide quantitative constraints on nappe geometries, burial depths, shortening, and kinematics, which are used as boundary conditions for thermal modeling. RSCM thermometry performed on 71 samples yields peak temperatures (TRSCM) ranging from 140 ± 20 °C to 341 ± 10 °C, systematically increasing with structural depth and toward internal domains. Maximum temperatures are recorded in the inner Subalpine footwall, the deeper nappes (notably the Albenga Nappe), and the Briançonnais units. The thermal overprint in the Subalpine Zone is interpreted as syn-orogenic tectonic burial, supported by the Eocene–Oligocene age of the sampled formations and the thermal continuity observed between nappes and para-autochthonous units. In contrast, a marked thermal inversion in the southwestern frontal sector, where a structural window exposes colder para-autochthonous rocks (~180 °C) beneath the warmer Sanremo Nappe (~250 °C), indicates inherited thermal contrasts during nappe emplacement. These structural and thermal constraints are used to parameterize a 1D thermo-kinematic model of nappe emplacement, in which geometries, thicknesses, and velocities are directly derived from the restored cross-sections. The model accounts for crustal heat production, conductive heat transfer, and basal shear heating. Model results show that the measured TRSCM values can be fully reproduced by syn-tectonic burial associated with thrust nappe emplacement, assuming a constant geothermal gradient of ~30 °C/km, consistent with independent estimates of paleo-burial depths and eroded overburden. Achieving a satisfactory fit between modeled and measured temperatures requires basal shear heating localized within a finite shear zone, with effective thicknesses ranging from ~4 to 35 m and systematically increasing toward the frontal parts of the orogenic wedge (foreland). The models imply up to ~11 km of eroded overburden in the hinterland and ~6 km in the foreland. Overall, this study demonstrates that structurally and thermally constrained 1D modeling provides a robust and internally consistent framework to quantify nappe emplacement, tectonic burial, and the kinematic architecture of the southwestern Alpine orogenic wedge.
How to cite: Tigroudja, L., Espurt, N., Scalabrino, B., Lahfid, A., Petit, C., and Fasentieux, B.: Reconstructing the Alpine crustal architecture of the Ligurian Flysch Nappes through integrated structural cross-sections, RSCM and constrained thermo-kinematic modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5396, https://doi.org/10.5194/egusphere-egu26-5396, 2026.
We present semi-automatically generated maps showing the variability of the stratigraphic thickness of the Helvetic Kieselkalk, a siliceous limestone-dominated geological unit which is widely exposed across different Helvetic nappes over more than 300 km along the Swiss Alps. The Helvetic Kieselkalk is commonly extracted to produce hard rock aggregates for the national road and railway infrastructure. The deposition of this unit onto the European (Helvetic) continental margin during the Early Cretaceous was affected by normal faulting, which lead to strong lateral thickness variations.
The Python and MATLAB approach used to create the thickness maps was developed as part of a Switzerland-wide mineral resource mapping project, funded by the Swiss Geological Survey (swisstopo). It is designed to rapidly generate large-scale map overviews of the stratigraphic thickness by analysing geological vector data such as the GeoCover dataset in Switzerland. The same approach is currently used in the framework of the swisstopo-funded Swiss Alps 3D project. There, automatically extracted and validated thickness data are used to improve the quality of the large-scale 3D geological model of the Swiss Alps.
Our results highlight an increase in thickness of the Helvetic Kieselkalk along the strike of the Alps from ca. 100 m in the western Helvetics (Wildhorn Nappe) to up to 1000 m in the eastern Helvetics (Drusberg and Säntis nappes). The depositional thickness was certainly affected by burial, folding and faulting during the formation of the Helvetic nappes. Nevertheless, two distinct thickness jumps indicate the presence of three sedimentary basins in east-west direction with a half-graben-like geometry. These thickness jumps coincide with present-day nappe boundaries and suggest that the inherited basin geometry influenced the formation of the Helvetic nappes.
The large-scale thickness maps and the improved undestanding of the paleogeography and tectonic evolution are helpful to identify stratiform mineral occurrences with favourable geometry and to refine 3D geological models.
How to cite: Nibourel, L., Galfetti, T., Musso-Piantelli, F., Furlan, M., and Heuberger, S.: Mapping large-scale thickness variations in the Helvetic domain (Switzerland) using a new semi-automated method, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12256, https://doi.org/10.5194/egusphere-egu26-12256, 2026.
The ALCAPA (Alps-Carpathians-Pannonia) megaunit, encompassing most of the Eastern Alps (Austroalpine units) and the Western Carpathians (Inner and Central part), has traditionally been interpreted to represent the Neo-Tethys-facing Permo-Triassic passive margin of Pangaea. Multiple tectonic units within the ALCAPA and wider Dinaridic-Balkanic domain have been regarded as continental sutures formed during the closure of the Neo-Tethyan Ocean. A long-standing debate concerns whether the Neo-Tethys comprised a single or multiple oceanic basins. In the ALCAPA region, the Neo-Tethys is commonly called the Meliata-Hallstatt Ocean and considered to represent an oceanic branch located south (in present-day coordinates) of the salt-rich Austroalpine-Carpathian passive margins. This interpretation assumes a simple and linear arrangement of Permo-Triassic facies, from shallow water platforms in the north to pelagic and bathyal deposits in the south. This facies scheme has been generally used as the basis to explain the distribution of Permo-Triassic units in the present-day fold-and-thrust belts.
Recent advances in the understanding of salt tectonics and passive margin geodynamics, however, calls this linear paleogeographic model into question. In this contribution we present new observations from the Inner Western Carpathians and a reevaluation of the Austroalpine domain and argue that the Permo-Triassic palegeography of ALCAPA was far more complex than previously assumed. We propose that the Permo-Triassic rift system formed an anastomosing network of rift branches, some of which remained aborted while others progressed to continental breakup and mantle exhumation. This evolution produced a complex mosaic of microcontinental blocks separated by rift basins and domains of exhumed subcontinental mantle, in stark contrast to the conventional linear continent-to-ocean model. This revised paleogeographic framework has significant implications for deciphering the distribution of Permo-Triassic facies in the pre-orogenic setting. Understanding the role of continental hyperextension in the ALCAPA also satisfactorily explains the frequent (and apparently incongruous) contacts of shallow crustal units on sub-continental mantle (e.g., evaporites or platform carbonates on serpentinized mantle).
We argue that Jurassic subduction nucleated preferentially along domains of Triassic exhumed mantle, and that recognizing the complex paleogeographic architecture substantially simplifies the tectonic interpretation of the subsequent Mesozoic evolution of the region. These observations further call for a redefinition of what is considered the Neo-Tethys Ocean within the ALCAPA domain.
How to cite: Fernandez, O., Köver, S., Fodor, L., Potočný, T., Csicsek, L. A., Ortner, H., Sanders, D., Molčan-Matejová, M., Plašienka, D., Mazur, S., Soni, T., Rowan, M. G., Muñoz, J. A., Manatschal, G., and Grasemann, B.: Revisiting the Late Permian – Jurassic paleogeography of the Eastern Alps and Western Carpathians and tectonic implications , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6587, https://doi.org/10.5194/egusphere-egu26-6587, 2026.
For decades, the Mesozoic geodynamics of the Balkan sector of the Alpine–Himalayan orogenic belt has been interpreted through contrasting geological and geodynamic models. Key debates have focused on the number of oceanic domains, the mode and timing of their closure, the mechanisms responsible for the emplacement of the Vardar Zone ophiolites, and the very existence of the enigmatic Sava-Vardar Zone (SVZ). In this contribution, we provide a synthesis of our recently published results together with ongoing numerical modelling efforts aimed at resolving the full complexity of Mesozoic Balkan geodynamics. To this end, we have used both 2D and 3D numerical geodynamic modelling based on the I2VIS and I3VIS codes, utilizing conservative finite-differences and marker-in-cell approach for solving the continuity, momentum and temperature equations.
While earlier models frequently invoked multiple oceanic basins, more recent studies have largely converged on a more parsimonious single-ocean scenario. Nevertheless, a major question persisted: how could compositionally and structurally distinct yet contemporaneous ophiolite belts have formed within a single Tethyan ocean? Our numerical models address this issue by demonstrating that a single NE-dipping subduction system can account for these contrasts, consistent with geological evidence indicating similar obduction ages on both the Europe- and Adria-derived continental units. In our models, this configuration leads to complete consumption of the ocean by the end of the Jurassic.
These results, however, stand in contrast to the widely held interpretation that a separate oceanic domain persisted into the Cretaceous – the so-called Cretaceous Sava Ocean. This idea came to prominence with the discovery of Upper Cretaceous basalts in the SVZ, initially interpreted as parts of ophiolite sequences. Subsequent work has shown this interpretation to be erroneous, leaving the subduction-like geochemical affinity of the Upper Cretaceous Apuseni–Banat–Timok–Srednogorie (ABTS) magmatic and metallogenic belt as the primary remaining argument. Our modelling demonstrates that the complex dynamics of an already-subducted Jurassic slab can generate this post-obduction magmatism, removing the need to invoke an active Cretaceous subduction zone. The model shows that in a post-obduction stage, a hydrated subducted slab undergoes detachment, rebound and subsequent partial melting, allowing for delayed subduction-like magmatism to occur after ocean closure.
The final unresolved issue concerns the origin of the Upper Cretaceous magmatism within the SVZ. We propose that these occurrences reflect localized reactivation of the suture in response to strike-slip motion between the European and Adriatic plates, producing zones of transtensional opening along the former plate boundary. New 3D numerical models support this interpretation, demonstrating that transtension can indeed reactivate a suture and generate mantle-derived magmatism within associated pull-apart basins.
How to cite: Stanković, N., Cvetković, V., Balázs, A., Prelević, D., Mladenović, A., Cvetkov, V., and Gerya, T.: Of slabs, sutures and ophiolites: Reinterpreting the Mesozoic geodynamics of the Balkan peninsula supported by numerical modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-425, https://doi.org/10.5194/egusphere-egu26-425, 2026.
The Cycladic Blueschist Unit (CBU) records Eocene-Oligocene high-pressure/low-temperature metamorphism across the Aegean, providing critical constraints on subduction-exhumation processes during Hellenic orogenesis. While extensively studied in the Cycladic islands, the CBU's northern continuation through the Olympos-Ossa-Pelion transect in mainland Greece remains poorly constrained, resulting in conflicting tectonic models regarding nappe emplacement mechanisms, thrust transport direction, and the timing of exhumation.
Multi-mineral Rb-Sr isochrons of syn-kinematic white mica allows us to link isotopic ages to specific deformation events. To resolve the four-dimensional tectonic evolution of the Olympos-Ossa-Pelion transect, we present 34 new Rb-Sr ages integrated with detailed structural and metamorphic analysis. Our results reveal three distinct episodes of high-pressure metamorphism with systematic along-strike variations: (1) In the Olympos-Ossa region, the Ampelakia Unit (CBU equivalent) records peak metamorphism at 48–41 Ma with top-to-SW kinematics and syn-orogenic exhumation at ~40 Ma, correlating with the Middle-CBU nappe in the Cyclades; (2) The underlying Olympos-Ossa Unit (Basal Unit equivalent) experienced high-pressure metamorphism at 34–26 Ma during continued SW-wards underthrusting, with syn-orogenic exhumation starting at ~28 Ma; (3) In the Pelion region, the Pelion Blueschist Unit (also a CBU equivalent) yields preliminary high-pressure metamorphic ages of ~27 Ma, followed by (sub)greenschist-facies top-to-NE shearing at 22 Ma and 14 Ma, potentially representing the equivalent of the Bottom-CBU nappe in the Cyclades. Exhumation of the CBU in the Olympos-Ossa-Pelion transect occurred in two stages: (1) Eocene to Oligocene syn-orogenic extrusion driven by simultaneous top-to-NE normal faulting above and top-to-SW out-of-sequence thrusting below; followed by (2) Miocene post-orogenic extension accommodated by top-to-the-NE detachment faults synchronous with Aegean-wide slab rollback. These findings bridge the geochronological gap of CBU nappes between mainland Greece and the Cyclades, providing direct age constraints on the timing of underthrusting and exhumation for the northern sector of the Hellenic high-pressure metamorphic belt.
How to cite: Hong, Y., Glodny, ., Romer, R., Skelton, A., Peillod, A., and Ring, U.: Resolving the chronological gap in the Olympos-Ossa-Pelion transect: New Rb-Sr constraints on Cycladic Blueschist Unit subduction and exhumation in mainland Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5855, https://doi.org/10.5194/egusphere-egu26-5855, 2026.
Miocene crustal extension in the Cyclades resulted in the development of major low-angle detachment systems, typically juxtaposing the Cycladic Blueschist Unit (CBU) in the footwall against the Pelagonian Unit (PU) in the hanging wall. Although the footwall CBU is well-documented, the PU hanging wall remains poorly understood in the western Cyclades due to extensive erosion. This study presents new geological, geochronological, and thermochronological data from two uninhabited islands, Makronisos and Agios Georgios, to better constrain the architecture and displacement of the West Cycladic Detachment System (WCDS). Our results demonstrate that Makronisos constitutes part of the WCDS footwall, with Raman spectroscopy of carbonaceous material temperatures of ~450°C indicating it belongs to the Lower Cycladic Nappe of the CBU. The island preserves intense top-to-SSW shear strain localized within marble ultramylonites, correlative with structures on neighboring Kea. New white mica 40Ar/39Ar ages indicate Middle to Late Miocene deformation, consistent with CBU exhumation documented elsewhere along the WCDS. Conversely, Agios Georgios represents a hanging-wall remnant situated structurally above the WCDS. It comprises Triassic granitic orthogneiss and metasediments that underwent upper greenschist to amphibolite facies metamorphism. New U-Pb zircon dating confirms an Early Triassic magmatic protolith, and 40Ar/39Ar and zircon (U-Th)/He data reveal a Late Cretaceous-Paleogene metamorphic overprint followed by cooling to shallow crustal levels by c. 20 Ma. The lithological and tectonometamorphic evolution of Agios Georgios closely matches the Vari and Akrotiri units of Syros and Tinos, respectively. This correlation extends the known distribution of Late Cretaceous-Paleogene Pelagonian domain remnants ~100 km westward. The divergent thermal histories, Miocene cooling in the footwall versus Paleogene cooling in the hanging wall, constrain a total WCDS displacement of 20-30 km between 20 Ma and 8 Ma, yielding an estimated slip rate of 1.5-2.5 mm/yr.
How to cite: Grasemann, B., Schneider, D. A., Soukis, K., Huet, B., Lindner, K., Loisl, J., Rice, A. H. N., Lozios, S., Draganits, E., and Rogowitz, A.: Don’t leave me hanging: Where is the hanging wall in the western Cyclades (Greece)?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5400, https://doi.org/10.5194/egusphere-egu26-5400, 2026.
In areas of prolonged extensional deformation, subsequent crustal thinning creates pathways for magma to ascend to shallow crustal levels, leading to a complex interplay between extensional deformation and magmatism with strong feedback. Numerical modeling can provide valuable insights into the involved processes and their temporal evolution.
The Attic-Cycladic Crystalline Complex (ACCC, central Aegean, Greece) formed as a result of prolonged syn- to late-orogenic exhumation, the latter associated with subduction zone retreat in the Neogene to recent. Late-orogenic exhumation was achieved through low-angle crustal-scale detachment systems rooted in the brittle-ductile transition. At present, the central part of the ACCC is generally aseismic, with major active faults and earthquake activity located along the north and, especially, the southern margins. The southern margin also hosts a large part of the modern volcanic arc, which has been established since the Pliocene. At the southeastern margin, the NE-SW Santorini–Amorgos basin represents a complex horst-and-graben structure with sediments exceeding 1000m in thickness. It is characterized by marginal and internal NE-SW oblique-slip normal faults with a significant dextral sense of motion, such as the Santorini–Amorgos Fault Zone, where the > 7 Mw 1956 Amorgos earthquake occurred. In January-March 2025, swarm-type earthquakes with magnitudes 1≤M≤5.2 were recorded, with hypocenters at depths mainly between 4 km and 15 km, concentrated along a narrow zone extending offshore of Santorini near the Columbo volcanic center towards the NE and south of Amorgos Island.
A plane-strain numerical model was constructed in the NW-SE extension direction to investigate the structural evolution of the region, driven by combined tectonic forces and magmatism. Simulations were performed using a large-strain finite-difference software in two stages. The first stage of the simulation aimed to recreate the basin's structure without interference from magmatic activity. In the second stage, a magmatic chamber was introduced at the weakest point within the obtained structural configuration of the first sequence. The application of this numerical model highlighted key aspects of the interplay between tectonics and magmatism. It successfully simulated the present structural configuration of the Santorini-Amorgos basin and the January-March 2025 swarm-type earthquakes resulting from the initiation and propagation of new cracks, above the brittle-ductile transition.
How to cite: Soukis, K., Maria, S., Haralambos, K., Emmanuel, S., and George, E.: The structure and evolution of the Santorini-Amorgos basin: numerical modelling simulation of the interplay between extensional deformation and magmatism, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18811, https://doi.org/10.5194/egusphere-egu26-18811, 2026.
Subduction dynamics in the Mediterranean realm is largely controlled by the Eurasia-Africa convergence and by the protracted accretion, since the late Cretaceous, of successive oceanic domains and microcontinents to the overriding Eurasian margin. Among these processes, basal accretion of coherent tectonic slices at the base of the forearc domain is one of the most difficult to investigate, as it occurs at high depth along the subduction interface and is only rarely preserved in the geological record. Yet, basal accretion is of prime importance, as it is suspected to remain active beneath active Mediterranean subduction zones and to contribute to the deformation and topographic signals monitored along them. To assess the spatial and temporal scales of the accretion-controlled forearc dynamics, it is therefore crucial to constrain the sequence of slicing episodes forming deep accretionary duplexes.
We address this issue through an integrated structural, petro-metamorphic and geochronological study of a high-pressure/low-temperature paleo-duplex exposed in western Crete and formed along the Hellenic subduction zone during the Oligocene–Miocene. We combine field-based structural mapping, petrological characterization, Raman spectroscopy on carbonaceous material, thermodynamic modelling, Rb/Sr multi-mineral geochronology and zircon (U–Th–Sm)/He thermochronology to identify distinct tectono-metamorphic slices, quantify their peak pressure–temperature conditions and constrain their timing of accretion and exhumation.
Our results reveal a dome-shaped nappe stack composed of five tectono-metamorphic units bounded by major shear zones, with a systematic down-stepping of peak temperatures (~450 to ~350 °C), pressures (17–18 to 7–8.5 kbar) and Rb/Sr ages (~26 Ma and ~15 Ma) toward lower structural levels. These indicate five basal-accretion episodes that successively migrated to shallower depths (~55–60 km to ~25–30 km) between the late Oligocene and middle Miocene. Subsequent fast exhumation of the duplex, with rates of ~3-11 mm/yr, decreasing to ~2-4 mm/yr at shallow levels, was mainly accommodated by top-to-the-N and subordinate top-to-the-S detachments associated with trench-perpendicular extension, intermittently overprinted by trench-parallel deformation.
This study further suggests a sequence of ~2-3-Myr-long deep slicing events, providing a critical timescale for trackingthe tectonic and topographic signatures of deep mass fluxes along active forearc margins in the Mediterranean region and beyond.
How to cite: Menant, A., Glodny, J., Angiboust, S., Sobel, E., Bessière, E., Jolivet, L., Augier, R., and Oncken, O.: Setting the sequence of deep slicing events along the Hellenic subduction zone from the P-T-t evolution of the HP-LT Cretan paleo-accretionary duplex (Greece), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13468, https://doi.org/10.5194/egusphere-egu26-13468, 2026.
Posters on site: Thu, 7 May, 10:45–12:30 | Hall X2
Creating data-driven realistic numerical models of certain regions on Earth is a challenging task, as a large number of input parameters are required to constrain the subsurface structure. These input parameters range from geometric parameters describing e.g. slab configurations to rheological input parameters.
With the advent of AdriaArray and related scientific initiatives, a large amount of geophysical, geodetic and geological datasets will become available. Interpreting these datasets together to create consistent interpretations and to facilitate meaningful data-driven numerical models remains problematic. This is due several issues: 1) formats of geoscientific datasets range from ASCII files to netCDF files, with the data often being ordered in different ways and 2) different datasets may have different spatial dimensions, depending on whether they relate to volume, surface or point data. With the julia-based open-source package GeophysicalModelGenerator.jl, a toolbox to merge and process such diverse datasets has been recently become available.
However, to interpret these merged datasets in an efficient manner, additional tools are required. Here we present the software package AdriaArrayGeometryPicker.jl that allows to visualize and interpret a large variety of datasets with a graphical user interface. We show how taking into account different datasets may help their interpretation, but also how different datasets may result in vastly different interpretations.
How to cite: Thielmann, M. and El-Sharkawy, A.: Tools for the joint interpretation of geoscientific datasets: the AdriaArray GeometryPicker, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17118, https://doi.org/10.5194/egusphere-egu26-17118, 2026.
The thermo-tectonic evolution of the Western Mediterranean realm reflects the superimposition of several orogenic phases inclusing the Pyrenean convergence, the Alpine collision and subsequent back-arc extension related to the opening of the Liguro-Provençal Basin. However, the long-wavelength geodynamic forcing driving this evolution remains debated. Most reconstructions rely either on basement-derived thermochronology or on basin-scale stratigraphic records, leading to segmented and sometimes conflicting interpretations. Here, we present a coupled thermochronological approach integrating crystalline basement massifs and their sedimentary cover to reconstruct the continuous geodynamic evolution of southeastern France within the Western Mediterranean realm from the Cretaceous to the Oligo-Miocene. We combine apatite and zircon fission-track and (U–Th)/He data from the Maures–Tanneron and Pelvoux crystalline massifs with new oxy-hydroxide (U–Th)/He constraints from karst-hosted bauxites and subalpine sedimentary systems of the Vocontian Basin. These datasets are jointly interpreted to derive regionally consistent time–temperature paths.
Results reveal a coherent lithospheric-scale thermal signal characterized by (i) mid-Cretaceous oxide crystallization related to Durancian Isthmus uplift, coeval with heating of the crystalline massifs, (ii) Late Cretaceous to Paleogene heating followed by cooling of bauxites driven by flexural and tectonic burial during Pyrenean convergence, synchronous with exhumation of adjacent crystalline massifs, and (iii) Oligo-Miocene heating and cooling associated with Liguro-Provençal back-arc rifting. These thermal trends are independently supported by U-Pb calcite ages documenting brittle deformation and fluid circulation within subalpine and Vocontian basins.
Basement and cover record synchronous thermal responses, while U-Pb calcite ages constrain the brittle response of sedimentary basins to the same lithospheric-scale deformation, indicating that sedimentary basins acted as passive recorders of lithospheric-scale forcing rather than isolated depocenters. This coupled approach demonstrates that long-wavelength geodynamic forcing controlled both exhumation of crystalline massifs and subsidence of adjacent basins, providing a unified thermo-tectonic framework for the Western Mediterranean realm.
How to cite: Boschetti, L., Mouthereau, F., Schwartz, S., and Rolland, Y.: Basement-cover thermochronological coupling reveals lithospheric-scale geodynamics in the Western Mediterranean realm (South-East France), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12576, https://doi.org/10.5194/egusphere-egu26-12576, 2026.
Abstract
The Simplon normal fault in the Western Alps caused tens of kilometers of orogen-parallel extension during convergence of the European and Adriatic plates, but the slip rate of the fault and the time when normal faulting ended are still debated. Here, we constrain the slip history of the Simplon fault with low-T thermochronology and thermo-kinematic modeling (Wolff et al. 2024). Closely spaced samples from an elevation profile in the center of the fault yield zircon (U-Th)/He ages (ZHe) that are nearly invariant over an altitude of 1.4 km and cluster around ~6 Ma. In contrast, apatite (U-Th)/He ages (AHe) increase with altitude from 3.4±0.3 to 4.6±0.7 Ma, while the AFT ages range from 4.4±0.7 to 5.8±1.5 Ma. In addition, recently published 40Ar/39Ar ages constrain that our samples moved through the brittle-ductile transition (i.e., ~300°C) at 8–10 Ma. Our thermo-kinematic inverse modeling shows that these age data can be explained by a single phase of normal faulting, which lasted from 19.8±1.8 to 5.3±0.3 Ma and caused 45±10 km of extension. The slip rate of the 30°-dipping model fault is 3.5±0.3 km/Myr and equivalent to an exhumation rate of ~1.8 km/Myr. Our modeling reveals that the altitude-dependent difference between ZHe and AHe ages reflects the thermal relaxation after faulting stopped at ~5.3 Ma. Since then, exhumation by erosion continued at a rate of ~0.5 km/Myr. Remarkably, the end of slip on the Simplon fault coincides with the cessation of reverse faulting at 6±2 Ma in the external crystalline massifs of the Alps (Aar, Mont Blanc, Aiguilles Rouges) and with a decrease in strain rate by one order of magnitude at 5-4 Ma in the Swiss molasse basin and the Jura mountains. This temporal coincidence suggests that normal faulting in the internal part of the Alps ceased when plate convergence waned and the under-thrusting of European continental lithosphere beneath the Adriatic plate came to an end.
References
Wolff, R., Hölzer, K., Hetzel, R., Dunkl, I., Anczkiewicz, A.A. 2024. Late-orogenic extension ceases with waning plate convergence: The case of the Simplon normal fault (Swiss Alps). Journal of Structural Geology 179, 105049. https://www.doi.org/10.1016/j.jsg.2024.105049
How to cite: Wolff, R., Hetzel, R., Hölzer, K., Dunkl, I., and A. Anczkiewicz, A.: Late-orogenic extension ceases with waning plate convergence: The case of the Simplon normal fault (Swiss Alps), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1729, https://doi.org/10.5194/egusphere-egu26-1729, 2026.
Within the Alpine nappe stack of the Western European Alps, the Zermatt-Saas Zone (ZSZ) is a remnant of the Piedmont-Ligurian Ocean. The oceanic lithosphere formed in Middle-to-Late Jurassic times and was subducted during the Alpine convergence up to UHP-to-HP metamorphic conditions, between the Late Cretaceous and middle Eocene. The ZSZ consists of serpentinite, metabasite, and metasedimentary rocks that are interpreted as a metamorphosed ophiolitic assemblage. This rock assemblage records multiple stages of ductile deformation that developed during the Alpine subduction, collision, and exhumation. In this assemblage, chaotic complexes consist of metasediments with a matrix containing variable amount of carbonatic and quarzitic components, including metabasite (some with gabbro texture) and ultramafite elements. In this kind of rocks, clear primary structures are hardly preserved due to intense transposition developed under UHP and HP conditions. However, we detected poorly preserved primary features that allow to define this metasedimentary matrix as a former sedimentary mélange. Additionally, we envisaged some primary genetic processes for the protoliths formation such as: tabular basalt flows disrupted within ocean floor sediments; mass transport at the ocean floor, possibly from serpentinite and gabbro exposed at structural highs; mass transport from the continental margins and/or interaction with trench sediments. Close to serpentinite, some portions of this metasedimentary matrix are interpreted as metasomatic products. Alpine transposition affected also serpentinite and metabasite and determined pervasive reorganization of the lithostratigraphy, with the formation of hectometer-sized meta-gabbro bodies forming lenses wrapped by the UHP/HP transposition foliation of serpentinite. Serpentinite also includes meter-sized rodingite lenses and layers that are variably folded and disrupted into the dominant foliation, deriving from former gabbro dykes metasomatized at the ocean floor. Serpentinite contains millimeter-sized clinopyroxene and micrometer-sized zircon porphyroclasts that are partially recrystallized during transposition. Clinopyroxene and zircon porphyroclasts show trace element composition consistent with gabbro protoliths and therefore are actually interpreted as remnants of mafic veinlets that percolated serpentinite during ocean floor evolution. On the other hand, serpentinite also preserves Ti-condrodite porphyroclasts that formed during UHP metamorphism predating the pervasive foliation development. In addition, the tectono-metamorphic history predating the dominant fabric at the regional scale is composite and variable in adjacent portions of the ZSZ. These lithostratigraphic, structural and metamorphic data are compatible with the existence of a tectonic mélange, in which the metasedimentary cover displays preserved original features that are consistent with various types of deformed and transformed primary sedimentary mélanges. Thus, the ZSZ can be regarded as an ophiolitic polygenetic mélange formed by HP pressure transposition, which almost completely obliterated primary and tectono-metamorphic features.
How to cite: Zanoni, D., Gusmeo, T., Luoni, P., Rebay, G., and Spalla, M. I.: Primary and tectonic mélange in the eclogitic Zermatt-Saas Zone, Western Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13695, https://doi.org/10.5194/egusphere-egu26-13695, 2026.
In the Tauern Window of the Eastern Alps, Miocene exhumation is commonly linked to erosion driven by relatively high topography coupled to structural doming, yet erosion alone cannot account for the observed magnitude of unroofing of the once deep-seated rocks. Recent work by our group in the eastern Tauern sub-dome identified the Eastern Tauern Detachment System (ETDS), an Oligo-Miocene crustal-scale extensional fault network, but its contribution to the overall exhumation remains unresolved. We report eleven new apatite fission track (AFT) ages from a north-south transect in the footwall of the Schuhflicker Detachment that yield three distinct age domains: i) early Miocene dates in the northern limb of the sub-dome, separating younger late Miocene dates in the ii) sub-dome core and iii) the northern edge of the window. Because AFT dates can be biased by partial annealing and kinetic heterogeneity, apatite grain-specific chemistry was quantified via electron microprobe to calculate rmr0, a proxy for fission track annealing kinetics. Thermal history models incorporating rmr0 were generated for one representative sample from each of the three domains. Models yield plausible cooling rates in the sub-dome core from c. 11-7 Ma at ~17°C/Myr, whereas the northern limb cooled earlier and slightly more slowly (c. 19-13 Ma at ~12°C/Myr). Although Miocene cooling in the sub-dome core fits the tectonic model of unroofing via erosion during doming, the older AFT ages in the northern limb record cooling associated with exhumation of the footwall of the Oligocene Schuhflicker Detachment, suggesting ductile thinning and east-directed extension contributed to tectonic exhumation prior to, and synchronous with, Miocene doming. Based on this model, 19-22 km of exhumation has occurred in the eastern Tauern sub-dome between 30 Ma and 19 Ma. Our model attempts to account for the proposed >20 km of exhumation since the Oligocene that has been proposed for parts of the Tauern Window, and supports accelerated unroofing during the Oligocene to earliest Miocene. These results indicate a complex exhumation history that involves tectonic unroofing and surface processes, and demonstrate both the utility and limitations of incorporating apatite chemistry into thermal history modeling.
How to cite: Spalding, J., Schneider, D., Huet, B., and Grasemann, B.: More than erosion: Oligo-Miocene tectonic unroofing of the eastern Tauern Window resolved via AFT thermal history models accounting for grain-specific annealing kinetics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13681, https://doi.org/10.5194/egusphere-egu26-13681, 2026.
A striking difference along the Alpine Orogen is the style of collisional tectonics during the Oligo-Miocene, with the onset of escape tectonics in the Eastern Alps. The indentation of the Adriatic Plate into the Eastern Alpine Orogen resulted in the formation of conjugate dextral and sinistral strike-slip faults in the vicinity of the Tauern Window. Moreover, major changes occurred in the foreland of the Eastern and Southern Alps in the Early Miocene, with the cessation of the northern Alpine front propagation and the onset of thrusting along the Southern Alpine Front. In this study, we present new results from structural, stratigraphic and subsidence analyses of the eastern North Alpine Foreland Basin (NAFB).
Our results show an initial phase of foreland sedimentation in the eastern NAFB between ca. 33-28 Ma, followed by a period of strong, tectonically driven subsidence between ca. 28-25 Ma, ending with a phase of erosion and formation of the basin-wide erosional unconformity, the Northern Slope Unconformity (NSU). During this time, the rift-related Mesozoic normal faults of the European platform were reactivated and then capped by the NSU. We interpret this phase as an increase in the flexure of the subducting European Plate under the growing Alpine Orogen. Between 25-19 Ma, the eastern NAFB remained in a deep-marine, underfilled state with a gentle increase in subsidence. A major shift took place around 19-17 Ma with tectonic uplift, ranging from 200 m (absolute minimum) to 1200 m depending on uncertainties on paleo-water depths, and rapid sedimentary infill of the basin. We discuss the possible causes for this major tectono-sedimentary shift in the eastern NAFB in relation to changes in collisional tectonics within the Eastern and Southern Alps, including a potential Early Miocene slab break-off event beneath the Eastern Alps.
How to cite: Le Breton, E., Bernhardt, A., Neumeister, R., Heismann, C., Hülscher, J., Sanders, R., Grunert, P., and Handy, M.: Early Miocene tectono-sedimentary shift in the eastern North Alpine Foreland Basin and its relation to changes in tectonic style of the Eastern Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14417, https://doi.org/10.5194/egusphere-egu26-14417, 2026.
The NW-SE-trending Malta Graben is one of the main extensional structures of the Sicily Channel, whose tectonic evolution within the broader Africa-Eurasia convergent setting remains debated. We reconstruct the tectono-stratigraphic evolution of the Malta Graben since the Pliocene through the interpretation of seismic reflection profiles, integrated with bathymetric, geodetic, and seismological data. The Plio–Pleistocene succession is organized into syn-extensional sequences, which are bounded by unconformities and record the progressive development of the rift above a Miocene–Mesozoic basement. The structural architecture is dominated by high-angle normal faults and negative flower structures, which controlled the growth of the graben. Moreover, some normal faults remain active today, while some have been locally inverted, producing folding and a prominent seafloor bulge in the northern part of the Malta Graben. The geometry and distribution of these inverted structures indicate that contractional reactivation occurred in recent geological times, since the Upper Pliocene-Lower Pleistocene. We propose that these coeval extensional and contractional structures reflect differential foreland deformation style within the Sicily Channel in response to the Africa–Eurasia plate convergence. The Malta Graben is therefore a valuable natural laboratory for better understanding how foreland region responds locally to competing tectonic forces at major plate boundaries.
How to cite: Artoni, A., Chizzini, N., Qadir, A., Bongiovanni, S., Palano, M., Polonia, A., Le Breton, E., Gasperini, L., Maiorana, M., and Sulli, A.: The Malta Graben: Insight into recent tectonic activity in the Sicily Channel (Central Mediterranean Sea) in response to Africa-Eurasia convergence , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21815, https://doi.org/10.5194/egusphere-egu26-21815, 2026.
Mantle dynamics beneath the Adria region are characterized by a complex interaction of lithospheric and sublithospheric processes, reflecting its role within the broader geodynamic framework of the Central Mediterranean. Seismic tomography provides valuable constraints on present-day mantle structure. On other hand, recent geophysical-petrological studies also inferred the slab geometry beneath the Apennines, Dinarides and Calabrian. However, linking these observations to mantle flow and surface expressions remains a challenging task.
In this study, we establish a numerical framework linking regional seismic tomography and geophysical-petrological models with simulations of instantaneous viscous flow of the mantle, to evaluate their contributions to present-day dynamic topography. Our approach consists of two main steps. First, isotropic shear-wave velocity anomalies from a selected tomographic model are converted into three-dimensional temperature and density fields. Second, these density anomalies, together with prescribed rheological laws, are used to compute instantaneous mantle flow by solving the Stokes equations, from which normal stresses at the surface are derived to estimate dynamic topography. In this second stage, we consider the previously modeled slab geometries to better define the viscosity boundaries.
The model domain is defined as a three-dimensional Cartesian volume extending from 30°N to 51°N in latitude, from 10°W to 36°E in longitude, and down to a depth of 660 km. The conversion from seismic velocities to temperature and density is performed using the V2RhoT_gibbs Python tool, which relies on Gibbs free-energy minimization and pre-computed thermodynamic lookup tables for a given mantle composition. Several material models are explored in order to better capture both lithospheric and asthenospheric structures.
The resulting density fields are implemented in the open-source geodynamic code ASPECT to compute the instantaneous mantle flow and its surface response. Different rheological scenarios are investigated, ranging from constant viscosity to temperature- and stress-dependent diffusion–dislocation creep laws. We present preliminary results illustrating the inferred mantle flow patterns and associated dynamic topography, and discuss their implications for the present-day dynamics of the Adria region.
How to cite: Ortega-Gelabert, O., Jiménez‐Munt, I., Kumar, A., García‐Castellanos, D., Bott, J., Najafi, M., Llorens, M.-G., and Zlotnik, S.: Dynamics of the Adria region using mantle tomography, geophysical-petrological modeling and mantle flow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19848, https://doi.org/10.5194/egusphere-egu26-19848, 2026.
The central Mediterranean’s complex tectonic evolution is driven by the geodynamic interplay of the Adriatic microplate within the Eurasian-African convergence. Adria plays a pivotal role in the development of the surrounding orogenic systems, including the Alps, Apennines, Dinarides, and Hellenides.
So far, the sparse seismic station coverage in the western Balkans and eastern Mediterranean has limited the resolution of the tomographic models throughout that area. Today, with the deployment of the dense, high quality, AdriaArray network, the improved seismic coverage affords an unprecedented opportunity to image the lithospheric and mantle structure beneath Adria. These images provide new constraints on the mechanisms governing the complex double-sided subduction of Adria, particularly beneath the Dinarides and the Albanides–Hellenides system, where several key geodynamic questions remain debated and unsolved.
Here, we present the results of a preliminary analysis of continuous seismic data recorded at more than 1,500 stations, with the aim of inferring a new three-dimensional shear-wave velocity model. Using SeisLib, a Python framework developed by Magrini et al. (2022), we extracted teleseismic and ambient noise surface-wave dispersion curves and then inverted them jointly to obtain phase velocity and group velocity maps for Rayleigh and Love waves over a wide time range (3–150 s). Through a Bayesian-probabilistic inversion approach (Magrini et al., 2025), the dispersion maps are converted into a large-scale, high-resolution 3D Vs model. In this framework, multiple data types with complementary sensitivity are inverted jointly, yielding a new image and a more robust characterization of the Adria lithosphere.
How to cite: Menichelli, I., Molinari, I., Cammarano, F., Boschi, L., Magrini, F., and Piromallo, C.: New Insights into the Adria lithosphere from Joint Inversion of Teleseismic and Ambient-Noise Surface-Wave Dispersion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9471, https://doi.org/10.5194/egusphere-egu26-9471, 2026.
Despite decades of extensive research, the precise lithospheric architecture and evolutionary trajectory of the Adria microplate, sandwiched between the converging Eurasian and African plates, remain subjects of intense geological debate. Although numerous paleotectonic models have been proposed over the last 100 years, the crustal evolution and dimensions of the Adria remain subjects of significant debate, often yielding conflicting results.
Conducted within the framework of the GeoAdria project, this study addresses existing tectonic uncertainties by integrating crustal-scale balanced and restored cross-sections with numerical lithospheric models. We investigate the structural architecture of the Apennine and Dinaride fold-and-thrust belts and their shared Adriatic foreland. Our numerical modeling results reveal a deep-seated lithospheric structure defined by two distinct lithospheric slabs with opposite dips. We interpret the slab beneath the Apennines as the western Adriatic continental lithosphere, which was originally contiguous with the Ionian Ocean. Conversely, the slab beneath the Dinarides represents the eastern continental margin of Adria, formerly adjacent to the consumed Vardar Ocean. These opposing slabs are interpreted as the products of continental delamination triggered at the end of oceanic subduction.
Quantitative analysis of a 758-km-long transect across southern Adria, indicates a minimum total shortening of 291 km (~28%). Of this total, 148 km (31%) was accommodated within the Southern Apennines, while 143 km (25%) occurred in the Southern Dinarides. Based on these numbers, we conclude that the Adria microplate had a minimum NE-SW width of 1050 km during the Jurassic, and thus between 126 and 621 km narrower than suggested by previous paleogeographic reconstructions.
By assuming basement area preservation, we calculated a restored Jurassic crustal thickness of 23–28 km for the central and eastern Adria domains. This crustal framework facilitated a paleogeography of shallow-water carbonate platforms limited from deep basins steep slopes analogous to the modern Bahamas Carbonate Platform.
In this geodynamic frame, we reconstruct the Adria microplate as an integral part of the African plate prior to the breakup of Pangea (~250 Ma). In this configuration, Adria was situated south of the subducting Paleo-Tethys Ocean, allowing for a direct connection between the shelf-basin systems of Southern Adria and the Pelagian Basin offshore Tunisia. Following the fragmentation of the African margin, Adria drifted toward the NNE, eventually reaching a position near the Eurasian margin as Paleo-Tethys subduction was almost consumed at this paleolatitude. This migration occurred during the Early–Middle Jurassic, preceding the Middle–Late Jurassic opening of the Ligurian-Tethys Ocean between Iberia-Eurasia and Africa.
This research is funded by the GEOADRIA (PID2022-139943NB-I00) project from the Spanish Government
How to cite: Vergés, J., Bravo-Gutiérrez, E., Torne, M., García-Castellanos, D., Negredo, A. M., Zhang, W., Cruset, D., Viaplana-Muzas, M., Najafi, M., and Jiménez-Munt, I.: Adria Microplate Structure and its Geodynamic History Since Early Mesozoic , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12737, https://doi.org/10.5194/egusphere-egu26-12737, 2026.
The Aegean arc represents the most prominent salient in the Mediterranean region and is characterized by large vertical-axis rotations along its limbs. Paleomagnetic studies along its western limb indicate that the external Ionian and Kruja zones of the Albano-Hellenides experienced ~40° of clockwise (CW) rotation relative to Africa/Adria, yet the timing of this rotation remains controversial. Previous interpretations have proposed either two (Miocene and Plio–Pleistocene) rotation episodes, or a single post mid-Miocene rotation accelerating along time. These uncertainties partly reflect the contribution of local thrust tectonics and/or strike-slip faults biasing the regional rotational trend.
We present new paleomagnetic data from 41 sites located in the virtually continuous Eocene-Early Pliocene sedimentary succession of the Tragjasi thrust sheet (Ionian zone, SW Albania). Sampled layers lie on the backlimb of a 50 km-long anticline subparallel to the regional orogenic trend and located away from major strike-slip faults. Eocene to early Early Pliocene sediments consistently record a 35°±9° CW rotation, demonstrating that rotation in the external Albanides began not earlier than the late Early Pliocene (~4 Ma).
Such new timing constraints were integrated into a quantitative kinematic reconstruction of the Aegean orocline over the last 20 Myr, developed in GPlates by combining paleomagnetic rotations with published kinematic models of the Peloponnese–Aegean domain. The reconstruction further integrates geophysical constraints on slab geometry and the amount of subducted oceanic lithosphere, allowing us to propose an updated kinematic evolution of the Aegean orocline.
Our results show that the post-Messinian tectonic evolution was characterized by synchronous CW rotation of the Albano-Hellenides and the Peloponnese, accompanied by a marked acceleration of subduction rates. We interpret this kinematic reorganization as due to multiple geodynamic processes, including (i) enhanced slab pull driven by the subduction of ~150 km of negatively buoyant Ionian (Neo-Tethys) oceanic lithosphere, (ii) mechanical coupling across the Kefalonia-Lefkada Fault, (iii) westward propagation of the North Anatolian Fault into the Aegean region, and (iv) the progressive development of a slab tear beneath the southern Dinarides. Together, these results highlight the tight coupling between slab dynamics and oroclinal bending in the late Cenozoic evolution of the Aegean orocline.
How to cite: Feriozzi, F., Speranza, F., Siravo, G., Le Breton, E., Cipollari, P., Faccenna, C., and Spagnuolo, L.: Timing of rotation and kinematic evolution of the Albano-Hellenides within the Aegean orocline, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6876, https://doi.org/10.5194/egusphere-egu26-6876, 2026.
The initiation of a subduction zone is commonly characterized by rapid dynamic refrigeration of the subduction channel, resulting in an inverted thermal gradient due to underthrusting of the cold oceanic slab. This rapid initial cooling after subduction initiation is recorded by metamorphic rocks, referred to as the metamorphic sole, that were progressively accreted along the base of the upper-plate mantle wedge. The metamorphic sole is often characterized by highly attenuated, discrete tectonic slivers of early underplated material commonly classified as an upper high-temperature granulite or amphibolite and a lower low-temperature greenschist. Determining the metamorphic ages of the different slivers of the metamorphic sole itself and the associated surrounding HP-LT schists provide critical insights into subduction initiation.
A high-temperature and low-temperature metamorphic sole has been proposed on in Tinos Island, Greece, above the Attic-Cycladic Crystalline Complex, allowing for the study of subduction initiation and early stages of the Cycladic Subduction Complex (CSC). This metamorphic sole lies beneath the metamorphosed late Jurassic Tsiknias Ophiolite suite (161.9 ± 2.8 Ma) and above the early Eocene HP-LT metamorphosed Cycladic Blueschist Unit (CBU). This proposed metamorphic sole was likely further sheared and attenuated during Miocene crustal-scale extension, accommodated along the North Cycladic Detachment system.
Samples from the Tinos metamorphic sole at the base of the Tsiknias Ophiolite are characterized by garnet amphiboles above greenschists. Petrochronological data from the metamorphic sole is scarce but provides important information. Previous work has dated a leucodioritic vein within the metamorphic sole as Late Cretaceous (74 ± 3.5 Ma). This study provides new U-Pb petrochronological data for both the high- and low-temperature metamorphic sole rocks that provide new insights into the early tectono-metamorphic evolution of the Cycladic subduction complex prior to early Eocene peak HP-LT metamorphism.
How to cite: Turek, S., Stockli, D., Soukis, K., and Laskari, S.: Determining the Timing and Type of Subduction Initiation Along the Cycladic Subduction Complex: The High and Low Temperature Sole in Tinos Island, Greece., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14858, https://doi.org/10.5194/egusphere-egu26-14858, 2026.
A correlation of the tectonostratigraphy and tectonic structures across the Attic-Cycladic belt to the Dodecanese islands and the western Menderes massif is required to reconstruct the pre-Eocene high pressure-subduction crustal architecture of the eastern Mediterranean. Notable, the transition from Cyclades to Dodecanese resides above a subduction slab tear that formed in the Miocene, which has offset the downgoing plate by >100 km, yet few tectonic structures exposed at the surface record the deeper geodynamic phenomenon. Residing along the NE-SW striking Santorini-Amorgos Fault Zone, the Astypalaia Platform exposes unmetamorphosed to weakly metamorphosed Triassic-Cretaceous neritic limestones, including Rudist- and Megalodont-bearing units. Unconformably above the limestone is an Eocene Nummulitic limestone-flysch package that contains km-scale marble and mafic volcanic olistoliths. The sequence, here named Analipsi subunit, was deformed into a series of NW-SE trending upright folds that preserves ductile top-to-N structures. The Vardia subunit, a weakly deformed Jurassic(?)-Cretaceous marble and limestone sequence capped by Eocene flysch, was thrust northward over the Analipsi subunit along the Vardia Thrust. This contact is characterized by a ductile strain gradient that increases toward the base of the hanging wall, marked by several tens of meters of marble ultramylonites on top of cataclasites. Top-to-S cataclasis overprints the earlier shortening structures localizing at the base of the Vardia Thrust. Unlike the other Dodecanese islands to the east, neither Variscan nor Paleozoic rocks are exposed on Astypalaia, indicating a higher structural level is present. Zircon (U-Th)/He dates from eight Eocene Analipsi flysch samples are partially reset, yielding single crystal ages of 130 Ma to 30 Ma, lacking a correlation to effective uranium concentrations, and exhibiting a dominant Paleocene-Early Eocene population. The overlap of the younger ZHe cooling dates and the depositional age of the Nummulite-bearing flysch suggests deposition, lithification, and subsequent deformation occurred rapidly in the Middle to Upper Eocene and under shallow crustal (<200°C) conditions. We propose that the Analipsi and Vardia subunits are part of the Pelagonian domain, which were imbricated after deposition of the Eocene flysch as the high pressure Cycladic Blueschist Unit was subducted beneath it. Although the magnitude of top-to-S extension on Astypalaia is significantly lower than the displacements recorded along the Oligocene Kalymnos and Kos detachments to the east, we correlate these events to argue that the transition from subduction to extension is constrained to 35-30 Ma, which occurred 20 Myr before the slab tear. This timing coincides with the onset of slab retreat throughout the Aegean region, mainly inferred from the migration of the volcanic arc.
How to cite: Schneider, D., Roche, V., Grasemann, B., and Soukis, K.: A quiet surface above a noisy slab: Eocene-Oligocene switch from shortening to extension on Astypalaia island, Aegean Sea, Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7872, https://doi.org/10.5194/egusphere-egu26-7872, 2026.
Active continental extension in the western Anatolia-Aegean (since approximately 25 Ma) drives exhumation of several metamorphic core complexes, low angle normal (detachment) faulting, and NE-SW and NW-SE trending strike-slip tectonics. However, the causative relationships among these processes and structures remain poorly understood. Here, we use 3-D thermomechanical numerical models to investigate how strain localization evolves in a stretching continent with plate rotations along a vertical axis. Namely, we test the obliquity of extension between 15° and 60°, the extension velocity of 1–2 cm/yr applied at the plate boundary, an initial crustal thickness of 50 km and a lithospheric thickness of 130 km, as well as the temperature gradient. To characterize the geometry of the fault systems, we calculate the Regime Stress Ratio (RSR) from the stress tensor and evaluate it in regions of high strain rate. We reconcile our model results with up-to-date structural features, including velocity fields from GPS, InSAR data, seismic receiver functions, and regional earthquake datasets from various sources. Preliminary results show that obliquity angle and initial layer thicknesses are first order parameters controlling strain localization, while simultaneously generating significant conjugate strike-slip tectonics. This is in accord with the formation of NE-SW and an array of NW-SE trending faults and clustering of earthquakes (relocated between 2010–2025) along the boundaries of the Gediz, Büyük Menderes and Simav grabens. These findings provide a modeling framework that links fault geometries, metamorphic core complex exhumation, and strike-slip deformation to the extensional tectonics and deeper lithospheric structure beneath the region.
How to cite: Aslan, C., Göğüş, O. H., Brune, S., Bodur, Ö., Li, K., Görgün, E., and Kekovalı, K.: Geodynamics of the Western Anatolia-Aegean Region: Linking tectonics and seismicity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1054, https://doi.org/10.5194/egusphere-egu26-1054, 2026.
The Alpine Tell and Rif orogenic belts of northern Algeria and Morocco formed in response to the southward closure of the Tethys Ocean from the Late Cretaceous onward. During the Cenozoic, it was associated with the coeval opening of the western Mediterranean basin and the collision between the AlKaPeCa blocks and the North African rifted margin.
While the pre-Mesozoic basement is accessible south of the Tell-Rif front, this basement is poorly exposed within the Tell-Rif orogenic belt where it remains largely unknown. Yet, the Tell-Rif basement bears key informations : (1) on the late Variscan collision between European blocks and Gondwana mainland with the potential existence of a Paleotethyan domain, and (2) on the Maghrebian Tethys evolution from Triassic rifting to Cenozoic closure.
In the Western Tell, especially in the Oran region, remnants of the North African margin basement occur in two types of outcrops: (1) a variety of xenoliths from the basement, including metamorphic and mafic rocks, that can be found within the Triassic salt-related structures and brought to the surface by the salt and (2) the “external metamorphic massifs”, affected by a subduction-related metamorphism of maximum Oligocene age, often associated with ultramafic rocks. Although these two complementary features offer a rare opportunity to sample the North African margin basement, it has almost never been studied.
In this work, we focused first on the xenoliths. An extensive sampling has been done within a dozen of Triassic salt related structures in the Oran region. These rocks are ranging from magmatic to high-temperature metamorphic rocks and can be either mafic or felsic. This vast diversity allowed us to do petrological studies as well as geochronological work (U-Pb on zircons) to characterise the basement, with a particular interest to the highest grade metamorphic rocks such as sillimanite-rich micaschists, kinzigites and mafic granulites.
The results provide a unique opportunity to better understand the North African margin basement composition and its Palaeozoic to Cenozoic geodynamic evolution.
How to cite: Patry, M., Leprêtre, R., Chabou, M. C., Hachemaoui, O., and Mohn, G.: Characterisation of the pre-Mesozoic basement within the Tell Orogeny (Northwestern Algeria ): Implications for the Tethys realm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12419, https://doi.org/10.5194/egusphere-egu26-12419, 2026.
The South Caspian Basin (SCB) is known as prolific petroleum province. The proven petroleum system is related with Oligocene-Miocene (Maikopian) marine type source rocks and Pliocene fluvial-deltaic sands, as a reservoir. Rich oil and gas fields are known in the northern and central part of the basin. At the same time in the south-western part of the basin a number of dry holes were drilled in early 2000’s. Overall the main reason of the failure was related with lack of charge.
Simultaneously, there is a distinct difference in structural shapes in two zones. The anticlines of the southern-south-western part of the basins have smaller wavelengths comparing with the anticlinal structures of the central South Caspian. This observation led to the question whether the difference in hydrocarbon behavior was related to the geodynamic nature.
South Caspian is genetically classified as a back-arc basin, whose evolution is closely linked to the subduction of the Neotethys oceanic lithosphere beneath the Eurasian continental margin during the Early Jurassic. Basin opening persisted until the early Late Cretaceous, followed by the progressive closure of the Neotethys Ocean. The subsequent collision of the Arabian Plate with the Eurasian Plate in the Late Cretaceous initiated a regional compressional tectonic regime, resulting in further subsidence and structural reorganization of the basin.
Tectonically, the basin can be subdivided into two distinct domains: an arc-distal zone, characterized by relatively wide and gently deformed structures, and an arc-proximal zone, marked by narrow, asymmetric, and intensely folded structural geometries. Variations in the thickness, burial depth, and rheological properties of the Maikop detachment layer exert primary control on this structural differentiation. In the central, deeply buried parts of the basin, increased gas saturation within the Maikop sequence reduces effective viscosity, facilitating detachment-controlled deformation.
From north to south, the detachment layer thins by more than a factor of two and becomes progressively shallower. This systematic variation governs the width and geometry of anticlinal structures: thin and shallow detachments favor the development of narrow and asymmetric folds, whereas thick and deeply buried detachments promote broader and more laterally extensive structures. Overall, arc-distal areas are characterized by a thick sedimentary cover and relatively low tectonic stress, while arc-proximal zones exhibit higher stress regimes and more intense deformation. Thus, the thickness and depth of the source interval in the southern portion of the basin lead to the lack of charge in that area.
How to cite: Asgarov, I., Bagirov, E., Farajov, A., and Bagirova, U.: Tectonic control of the petroleum system characteristics in the South Caspian Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16412, https://doi.org/10.5194/egusphere-egu26-16412, 2026.
