The release of carbon at plate boundaries strongly influences Earth’s long-term climate over geological timescales. Continental rifts, in particular, are thought to play a major role in CO₂ degassing by activating carbon reservoirs in the deep lithosphere, with magmatic rifting enabling efficient CO₂ transport via carbonate-rich melts, especially during the early stages of rift development (Foley and Fischer, 2017). Substantial uncertainties in global degassing rates remain, as the incomplete geological record limits precise constraints on the timing, magnitude, and controlling factors of rift-related CO₂ release.

To reduce these uncertainties and enable time-dependent estimates of CO₂ degassing at continental rifts worldwide, we quantify first-order rift characteristics that are expected to control CO₂ degassing. Our analysis employs automated geoinformation workflows and builds on a newly compiled global database of more than 1500 Phanerozoic rifting events, providing a systematic framework for quantifying rift properties.

Here, we focus on three key characteristics: (I) proximity to cratonic lithosphere as an indicator of access to deep carbon reservoirs, (II) crustal thickness as a proxy for rift maturity and tectonic evolution, and (III) the distinction between magmatic and non-magmatic rifting styles, as provided by the global rift database, reflecting differences in the role of magma and volatile transport pathways. Crustal thickness and craton proximity are evaluated using multiple global crustal models and alternative craton boundary interpretations. These characteristics are linked to published present-day CO₂ flux measurements from active rift systems to derive relationships between rift properties and degassing rates. In the future, we aim to use these relationships in conjunction with plate tectonic reconstructions to derive global, time-dependent CO₂ degassing estimates throughout Phanerozoic times.

References:
Foley, S. F., & Fischer, T. P. (2017). An essential role for continental rifts and lithosphere in the deep carbon cycle. Nature Geoscience, 1. https://doi.org/10.1038/s41561-017-0002-7

How to cite: Hirche, L., Brune, S., Heine, C., Williams, S., and Jentsch, A.: Global rift analysis of tectonic and magmatic characteristics: towards constraining rift-related CO₂ degassing over geological timescales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17798, https://doi.org/10.5194/egusphere-egu26-17798, 2026.

EGU26-17798

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The Central Kenya RIft (CKR) is one of the fastest deforming sections of the Eastern African Rift System (EARS). Extensive tectonic research has been performed on the rift in northern and southern Kenya, but the modern tectonic geomorphology of the CKR remains understudied. Existing fault maps show a change in the orientation of the EARS within the CKR, although faults have not been mapped in detail with modern techniques. Despite the numerous fault scarps that offset the rift floor, few large earthquakes have been recorded in the recent past, with the exception of a M_S 6.9 event in 1928. Maturing rifts demonstrate a shift from border fault seismicity to increased aseismic deformation dsitributed along intra-rift faults. This study aims to map active fault scarps within the CKR to better understand the modern tectonics, which may give insights into seismic hazard for an area with a high population growth rate. Rigorous examination of the high resolution TanDEM-X Digital Elevation Model (DEM) was used to formulate a digital fault database, which includes attributes about individual fault lengths and orientations. The NNW-SSE orientated CKR represents an intersection between NNE-SSW orientated EARS rifts to the north and south, and older NNW-SSE orientated structural fabrics. While the CKR itself shows a traditional mature rift morphology containing a developed inner graben with recent volcanism, the junction between the CKR and Northern Kenya Rift appears to be less mature. The 1928 earthquake, which occurred along a border fault in this junction, challenges the theory of axial strain concentration in an aging rift. Calculations on the balance of extension accommodated by larger border faults vs younger intra-rift grid faults allows for the possibility of continued border fault slip. The lack of large earthquakes in the CKR itself suggests an aseismic model to describe deformation, while seismic hazard appears to be greater in the junctions between rift segments of alternate orientations. 

How to cite: Botha, D., Sloan, A., Kübler, S., and Kahle, B.: Neotectonics of the Central Kenya Rift, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1035, https://doi.org/10.5194/egusphere-egu26-1035, 2026.

EGU26-1035

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The Natron Basin is located within the eastern branch of the East African Rift, a segment characterized by greater magmatic activity compared to the western branch. This activity has been shown to play a key role in accommodating deformation in the eastern rift, alongside crustal-scale faulting. The Natron Basin represents a particularly suitable natural laboratory to investigate the interaction between active tectonic and magmatic deformation, as previous studies have documented magmatic intrusion events associated with active rifting episodes in the region.

In this study, we use new geodetic observations acquired during a GNSS campaign conducted in the Natron Basin in summer 2025, and started in 2013, to investigate present-day deformation patterns. Campaign-derived horizontal (and vertical) velocities are used to estimate regional strain rates and to derive geodetic moment rates under standard mechanical assumptions. These geodetic estimates provide an integrated measure of ongoing extension across the basin.

To assess how this deformation is released seismically, we compare geodetic moment rates with seismic moment rates inferred from global earthquake catalogs, including NEIC and ISC; over comparable spatial and temporal scales. This comparison allows us to place bounds on the seismic coupling coefficient of rift normal faults.

The observed mismatch between geodetic and seismic moment rates suggest that a significant fraction of present-day deformation in the Natron Basin is accommodated though aseismic processes. These may include distributed crustal deformation and contributions from magma intrusions, which are known to influence rift evolution in magma-rich segments of the East African Rift. These observations illustrate the potential of combined geodetic and seismic analyses to investigate strain partitioning in magma-rich segments of continental rifts.

How to cite: Navarrete, I., Olive, J.-A., Calais, E., Keir, D., and Dalaison, M.: Strain partitioning in the Natron Basin, East African Rift: Insights from geodetic and seismic moment rates., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11130, https://doi.org/10.5194/egusphere-egu26-11130, 2026.

EGU26-11130

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The interaction between mantle plumes and continental lithosphere results in a complex spectrum of rifting outcomes, ranging from magma-rich breakups to failed rifts. Current research in the Turkana Depression posits a "Refractory Paradox," suggesting that failed rifts like the Anza Graben remain "dead zones" because prior melting events extracted volatiles, leaving behind a mechanically strong, dried-out lithosphere resistant to modification. However, it remains unclear if this "baked-dry" signature is a global requirement for rift failure or a local anomaly. We investigate this hypothesis by mapping the subtle architectural differences—specifically Moho sharpness and seismic lid preservation—that distinguish magma-poor regions from their magma-rich counterparts. To overcome the limitations of standard receiver function (RF) analysis, which is often degraded by noise and reverberations, we apply a rigorous, high-resolution workflow. We first denoise seismic data using the CRISP-RF algorithm, employing sparsity-promoting Radon transforms to suppress incoherent noise while preserving full-wavefield phases. These clean data are then inverted alongside surface wave dispersion measurements using a transdimensional probabilistic Bayesian  framework. This approach allows us to quantify non-uniqueness and robustly constrain multi-layered crustal properties (Vp/Vs ratios) and lithospheric velocity structure without placing limiting assumptions on elastic properties. By integrating these refined seismic constraints with common-conversion-point (CCP) stacking, we resolve the trade-off between magmatic underplating (gradational Moho, Vp/Vs > 1.8) and tectonic thinning (sharp Moho, Vp/Vs ~1.74). Finally, we pair these structural observations with thermo-chemical modeling (WINTERC-G/PerPleX) to convert velocities into temperature and composition. This study aims to determine if the lithospheric strength beneath the African Rift is governed by volatile depletion or alternative weakening mechanisms, such as anisotropy or eclogitization.

How to cite: Maenner, M., Legre, J.-J., Stamps, D. S., Adams, A., and Olugboji, T.: Unified Mapping of the African Rift System: Lithospheric Strength and Magmatic Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5886, https://doi.org/10.5194/egusphere-egu26-5886, 2026.

EGU26-5886

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The East African Rift provides a natural laboratory to study the influence of pre-existing lithospheric thin spots on the development of rifting and hotspot tectonism. Below the Ethiopian Rift and elevated Ethiopian Plateau, extensive magmatic and thermal modification due to Eocene-Oligocene flood basalt magmatism and Miocene-Recent rifting has resulted in slow lithospheric mantle velocities (< 4.1km/s; Dugda et al., 2007, JGR). In contrast, below the previously rifted, lower-lying Turkana Depression to the south, the lithospheric mantle appears relatively unmodified (4.2-4.8 km/s; Kounoudis et al., 2023, EPSL), despite being underlain by hot, mantle plume material. Important in this picture are detailed constraints on the lithosphere-asthenosphere boundary (LAB).

Why the Turkana Depression, and particularly the failed Anza Rift terranes, remained resistant to thermal and magmatic modification, is debated. Although the Turkana Depression was a lithospheric thin spot at the onset of plume magmatism, Cenozoic rifting is now circumnavigating, not exploiting, the Anza Rift terranes (Musila et al., 2023, G³). Lithospheric thin spots therefore don't necessarily mark weak zones that are exploited by subsequent rifting and magmatism. One hypothesis for the apparently refractory nature of the Anza lithosphere is that Mesozoic rifting removed easily fusible phases, suppressing subsequent melting and associated strain localisation (Kounoudis et al., 2025, Nature).

To test this geodynamic scenario, we calculated teleseismic S-to-p receiver functions and examined lithospheric thickness variations in the Turkana Depression, where the contrast between fast, relatively unmodified lithospheric mantle and slow, partially molten, plume-infiltrated asthenosphere is expected to provide impulsive S-to-p conversions at the LAB. We observe that the least impulsive and shallowest LAB conversions are associated with Miocene-Recent rift zones, and isolated shield volcanoes. Elsewhere, sharper and deeper S-to-p conversions attest to a lithosphere that has resisted thermo-mechanical modification.

How to cite: Ville, L., Bastow, I., Miller, M., Kounoudis, R., Renwick, B., and Ebinger, C.: LAB depth constraints from the Turkana Depression, East African Rift: implications for rifting and magmatism development in lithospheric thin spots, from S-to-p receiver functions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17705, https://doi.org/10.5194/egusphere-egu26-17705, 2026.

EGU26-17705

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The Dniepr–Donets Basin (DDB) is one of the largest and best-preserved intracontinental rift systems in Europe, yet the geodynamic processes responsible for its formation remain uncertain. There are two end-member models possible: (1) passive rifting driven by far-field tectonic stresses transmitted through the lithosphere, such as back-arc extension or plate boundary forces, and (2) active rifting associated with localized thermal anomalies in the mantle, potentially linked to plume-like upwellings. Distinguishing between these mechanisms is important for understanding why some continental rifts evolve toward oceanic break-up, whereas others, such as the DDB, remain confined within continental interiors.

This study aims to reassess the tectonic evolution of the DDB by integrating regional-scale seismic, borehole, gravity, and magnetic datasets into a coherent crustal and lithospheric framework. The core of the analysis is based on the interpretation of approximately 40 regional seismic reflection and refraction profiles, including classical and widely used datasets such as DOBRE’99 and Georift-2013. These seismic data are calibrated using stratigraphic, lithological, and velocity information from nearly 1,900 boreholes distributed across the basin. Fourteen key stratigraphic horizons are mapped consistently throughout the DDB, covering an area of ~76,900 km² and spanning the pre-rift, syn-rift, and post-rift sedimentary sequences.

Seismic interpretation is complemented by gravity and magnetic anomaly data, which are used to refine the geometry and continuity of major fault systems and crustal domains. The combined datasets allow the timing and kinematics of major faulting episodes and regional unconformities to be constrained with improved confidence. Balanced cross-section analysis along selected regional profiles provides quantitative estimates of crustal extension, fault displacement, and basin asymmetry, offering direct tests of competing rift models.

A three-dimensional structural model of the DDB that integrates seismic surfaces with borehole stratigraphy and velocity data is a key outcome of the work. Although still under development, this model reveals the three-dimensional architecture of the basin, including variations in sediment thickness, fault segmentation, and structural asymmetry along strike. Particular attention is paid to identifying systematic asymmetries in fault geometry and basin fill, which may indicate simple-shear deformation and lithospheric-scale detachment processes commonly associated with passive rifting. Linking shallow geological observations with deep crustal reflectivity patterns enables a more robust reconstruction of the basin’s long-term evolution.

Potential field data further provide constraints on the role of mantle processes during rifting. Spatial variations in gravity and magnetic anomalies are analyzed to detect possible mafic intrusions, high-density lower-crustal bodies, or anomalous mantle domains. These observations are used to evaluate whether thermal weakening of the lithosphere and magmatic underplating played a primary role, or whether rifting was dominated by mechanical stretching of a relatively cold lithosphere.

Overall, this ongoing research integrates crustal- and mantle-scale observations to explore the interplay between mantle dynamics, faulting, sedimentation, and basin subsidence. The results are expected to refine models of intracontinental rifting and clarify the conditions under which continental rifts either progress toward break-up or remain long-lived but abortive systems, as exemplified by the Dniepr–Donets Basin.

How to cite: Nasiri, A., Stephenson, R., Stovba, S., Drachev, S., Słonka, Ł., and Mazur, S.: Integrated Seismic–Potential Field Constraints on the Evolution of the Dniepr–Donets Rift Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9582, https://doi.org/10.5194/egusphere-egu26-9582, 2026.

EGU26-9582

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Many rift-related triple-junctions from various geological periods have been previously investigated worldwide. Some of these large extensional lithospheric phenomena even involved complex circular configurations composed of numerous omnidirectionally spaced radial and arcuate elements, thereby having a general multi-junction character. Although pointing to close association of horizontal plate kinematics with centrally directed vertical updoming as two conjugated significant geodynamic phenomena, such annular dichotomy of features penetrating and segmenting the surrounding upper Earth's mass has yet been addressed only poorly.

Based on spatial analysis of regional topography and/or hydrography, an extensive Cenozoic circular structure (> 6,000 km in diameter) even including recently active tectonic elements appears to have developed in whole Europe and some adjacent areas of Africa and Asia centred at a common intersection point of the Upper Rhine Graben, Lower Rhine grabens (with significant Roer structure), Hessian grabens (involving Leine structure), and more distant Eger Graben current axes. The pervasive surface fracturing of both higher / lower topographic levels was taken into account (numerous concentric boundaries between mountain summit blocks visualized by closed contours / ubiquitous multi-arc- and fan-shaped geometries within piedmonts and lowlands indicated in continental river network, less along important block-bounding slopes, and locally on sea floor). The fairly regular annular lithospheric fragmentation is expressed by a wide-scale spectrum of features from general mountain or basin belt orientations through trends of circumferential, centrifugal, or centripetal river sections and corresponding valleys to consistent sets of sharp stream bends.

Using a similar research approach, several analogous circular phenomena were detected within the Red Sea rift system. Despite possible links to various known geometrically consistent geological structures including magma plumbings or mantle plumes, it is yet hard to determine the main evolutionary processes and the closer time constraints of the circular systems. Their role should be considered and discussed on a broad disciplinary basis, among others, because similar surface configurations seem to exist in different tectonic settings such as large uplifting basement massifs or arcuate orogenic belts and intermontane basins. An attempt to invoke related communication is made also by means of this contribution.

How to cite: Roštínský, P.: Rhine Graben rift system-related multi-junction and other analogs: Large-scale circular lithospheric segmentation indicated in regional topographic and hydrographic data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2582, https://doi.org/10.5194/egusphere-egu26-2582, 2026.

EGU26-2582

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How to cite: Dall Asta, N., Denèle, Y., Hernandez Leal, M., Regard, V., Frayssignes, A., Hermant, B., Bonnet, S., Derian, M., Rouby, D., Angrand, P., and Bellanger, M.: Mechanical evolution of the wide diamond-shaped Española linkage zone, Rio Grande Rift: insights from structural analysis and analogue modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23214, https://doi.org/10.5194/egusphere-egu26-23214, 2026.

EGU26-23214

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The North Gulf of Evia is a young, active continental rift system located in Central Greece. Extension of 2-4 mm/yr is accommodated by large normal fault systems, such as the onshore Coastal Faults near Kammena Vourla, but slip rates and timing of initiation of these structures and intrabasinal offshore faults are poorly constrained. Extension is also coupled with strong rotational and strike-slip influence from the westward-propagating North Anatolian Fault, providing contrast to the nearby, orthogonal rifting in the Gulf of Corinth. The geodynamic setting of the rift has resulted in a complex configuration of normal, oblique and strike-slip faults across the North Gulf of Evia rift system. Detailed, high resolution study of faulting processes (initiation, linkage and migration) and the temporal evolution of such systems requires a high-resolution age model of syn-kinematic sedimentation. To date, no pre-Holocene sedimentary correlation has been proposed for the North Gulf of Evia, restricting the temporal scope of evolutionary studies.

We aim to unlock the temporal evolution of late-Quaternary (0-~325 ka) sedimentation and faulting in the North Gulf of Evia through the development of a syn-tectonic depositional age model for the Western Basin of the Gulf. To do this, we exploit a high resolution, high density 2D seismic reflection dataset (WATER I and II) to identify three key mappable horizons across the semi-enclosed basin using seismic stratigraphic principles including reflection terminations and onlap relationships. Based on observed late-Pleistocene deltaic clinoform packages, ages of ~12 ka (MIS 2), ~130 ka (MIS 6) and ~325 ka (MIS 9) are attributed to these horizons within our sequence stratigraphic model. The age model is applied across the Western Basin alongside a new network of offshore faults to determine the major structural components, depocentres and evolutionary history of the rift system for the first time.

We resolve the major modern structural controls on the basin to be the Kalypso Fault at the southern margin of the rift and the axial Central Graben. Holocene throw on the extensional Kalypso Fault is ~3.75 mm/yr with faults of the Central Graben deforming at throw rates of ~0.9 - 1.7 mm/yr. We show that the Kalypso Fault is linked to the western part of the onshore Coastal Fault System, widely considered the most active fault zone of the North Gulf of Evia and uplifts the hanging wall of the active Arkitsa Fault, where a sequence of uplifted Pleistocene marine terraces is preserved. Initiation of the Kalypso Fault is temporally constrained to ~325 ka from thickening relationships of syn-kinematic sediment packages following a strain migration event from the Arkitsa Fault. This migration event occurs across non-parallel structures with evolving strike of >20°, likely reflecting the regional rotational influence of the North Anatolian Fault on Central Greece. The Kalypso Fault represents the most active resolved normal fault in the Western North Gulf of Evia and presents significant, previously unrecognised seismic hazard.

How to cite: Wood, J., Bell, R., Whittaker, A., Coveney, S., Chanier, F., Caroir, F., Kranis, H., and Ganas, A.: Normal fault migration and basin evolution in complex rift settings: insights from the North Gulf of Evia, Central Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7348, https://doi.org/10.5194/egusphere-egu26-7348, 2026.

EGU26-7348

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In many areas of active faulting, the continuity of normal faults with a short or incomplete historical earthquake record and subtle topographic expression is not fully understood: as a result the seismic potential of these faults is often underestimated. The Southern Gulf of Evia rift, Greece is an example of a poorly explored normal fault bounded system, where the location and spatiotemporal evolution of the major basin bounding faults is not well constrained. We integrate geomorphic and structural field data, topographic analyses and geodetic data to constrain the locations, footwall geometries and structural evolution of 8 major extensional structures bounding the Southern margin of the South Gulf of Evia. We propose that this fault system comprises two isolated fault groups containing both partially and fully linked segments. These fault linkage scenarios suggest that the eastern fault group may have a total linked length of ca. 40 km with a maximum credible earthquake size of Mw 7.0. Further, we reconcile new analysis of vintage sparker seismic reflection data previously acquired and interpreted in the 1980s, with onshore geomorphic indicators of tectonic uplift to provide new constraints on the continuity of active normal faults offshore, including the major normal fault zones bounding the northern margin of the rift. By comparing our reconstructions of footwall relief with the seismic reflection and Ocean Bottom Seismometer (OBS) data, we suggest footwall uplift to hanging wall subsidence ratios of 1:2-1:3 and total slip rates in the order of 2-3 mm/yr. Finally, based on the correlation of seismic stratigraphy with a global eustatic sea level curve and a comparison of estimated sediment fluxes into the Gulf with measured sediment volumes in the South Gulf, we propose updated Pleistocene-Holocene ages for the basin stratigraphy and suggest possible timescales for fault evolution and linkage along the rift margins.

How to cite: Coveney, S., Whittaker, A., Bell, R., Wood, J., Kranis, H., and Ganas, A.: New constraints on active normal faulting in the South Gulf of Evia, Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7229, https://doi.org/10.5194/egusphere-egu26-7229, 2026.

EGU26-7229

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The Gulf of Argos, Greece, is a post-Miocene basin at the north-western extremity of the Cretan Sea (southern Aegean). Its formation is attributed to NE-SW-oriented back-arc extension, induced by rollback of the subducting slab in the Hellenic arc.

The western margin of the Gulf of Argos is marked by the almost linear coastline of the eastern Peloponnese, and is related to a c.100 km long, NNW-SSE normal fault system, stretching from Kiveri to Ariana. Despite it being a recognizable structure, there are few, if any, constraints related to its degree of activity, possible segmentation, and seismic hazard potential. The immediate footwall to this fault system, which we name Western Argos Fault System (WAFS), hosts several similarly striking high-angle normal faults, whose Quaternary degree of activity is also poorly understood.

To better understand fault activity and evolution in the Gulf of Argos, we study the mid- to long-term (several kyr to a few Myr) development of the footwall of the West Argos Fault System. Our study focuses on how drainage river long profiles and footwall relief have responded dynamically to tectonic activity. We estimate an uplift rate for each footwall catchment along the WAFS from knickpoint analysis and estimates of bedrock erodibility. We then compare these results with vertical motion data collected in the field and topographical data along the western margin of the Gulf of Argos.

We propose a throw rate of 0.9-2.4 mm/yr along the WAFS, which comprises at least four segments and an overall southward migration of fault activity, as the northernmost segments appear to be significantly less active than the southern ones.

How to cite: Viger, A., Kranis, H., Whittaker, A., Bell, R., and Ganas, A.: Fault activity along the western margin of the Argos Gulf (Peloponnese, Greece) revealed by tectonic geomorphology analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10165, https://doi.org/10.5194/egusphere-egu26-10165, 2026.

EGU26-10165

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From 5 to ca. 2 million years ago, faulting in the Corinth Rift, in central Greece, was concentrated onshore, to the south of the present-day Gulf of Corinth. Between 2 to 1.8 Ma the active fault network migrated northward, accompanied by footwall uplift, which led to active faulting and the rift being localized offshore in the present-day Gulf of Corinth. The factors controlling this fault migration remain unknown. Overall rift evolution is controlled by tectonics, but climate-driven surface processes affect rift topography, the development and longevity of normal faults, and overall rift evolution. A simple yet effective method for assessing strain distribution within a fractured region is the Kuiper’s test, which quantifies how much a line sampled through a faulted area deviates from a uniform distribution. By calculating the cumulative extension of faults distributed along a line, it is possible to infer if the strain in this section is distributed homogeneously throughout the fractures (values close to the uniform distribution) or if the strain is localized in few large faults (large departure of the uniform distribution), and whether this variation is statistically significant. We use the finite element thermo‐mechanical numerical model Fantom-2D coupled with the landscape evolution model FastScape to investigate how inheritance and surface processes control rift faulting and progressive localization during the early stages of continental rift evolution. We test different values of crustal strength and of frictional-plastic strain weakening to evaluate the response of the models. We tested each model without surface processes, and with different aggradation and progradation rates. We evaluated fault distribution, depocenter migration and rift localization through time and compared them to high resolution datasets from the present-day Corinth Rift and central Greece. The degree of localization obtained through the Kuiper’s test for five regions in the Corinth Rift were used to further validate the models. Using datasets of a rift system with a relatively simple extension history such as the Corinth Rift helps to better constrain numerical modelling parameters and improve rift evolution models.

How to cite: Barbosa, I., Huismans, R., Nixon, C., Gawthorpe, R., and Rouby, D.: Effects of inheritance and surface processes on strain localization during the early stages of the Corinth Rift system development , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8746, https://doi.org/10.5194/egusphere-egu26-8746, 2026.

EGU26-8746

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The Meso-Neoproterozoic period is sometimes referred to as the “Boring Billion” or “Earth’s Middle Age,” spanning the time between the formation of the Columbia supercontinent and the Rodinia supercontinent. This period records a key transition in the supercontinent cycle, shaping the global tectonic regime and paleogeographic pattern. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb geochronological analysis was conducted on five sandstone samples from the Ordos Rift Zone in the western North China Craton to constrain the regional tectonic evolution and basin development processes. The detrital zircon ages can be divided into multiple age groups, with zircon grains older than 1.8 Ga derived from the basement of the North China Craton, while the younger zircon populations (< 1.8 Ga) are associated with Mesoproterozoic magmatic events. Through an integrated approach combining zircon geochronology, major and trace element analysis, and sandstone modal analysis, the tectonic setting and parent rock properties of the provenance area were identified. The tripartite sedimentary cycle of volcanic rocks, continental-margin clastic rocks, and marine carbonate rocks in the Changcheng Period of the Ordos Rift Zone was finely delineated, and the response times (2.0  Ga, 1.8  Ga, and 1.6  Ga) of the assembly, consolidation, and breakup processes of the Columbia supercontinent in the western North China Craton were calibrated, respectively. The results show that the vertical sedimentary sequence of the Changcheng System in the Ordos Rift Zone corresponds to the rift evolution stages, forming a tripartite evolutionary cycle of igneous rocks–continental-margin clastic rocks–marine carbonate rocks, which records the transition process of tectonic activity from intense to stable. Three distinct stages of basin evolution during 1.8–1.4 Ga were defined: the initial rift stage and the rift expansion stage correspond to the disintegration of the Columbia supercontinent (1.8–1.6 Ga), and the passive continental margin stage coincides with a slowdown of the late supercontinent breakup rate (1.6–1.4 Ga). The detailed characterization of the regional tectonic evolution and rift zone sedimentary filling process during the Changcheng Period in the Ordos Basin reveals the source‑to‑sink spatiotemporal sedimentary pattern controlled by the rift system, providing key constraints for the evolution of the western margin of the North China Craton during the Precambrian supercontinent transition and offering new insights into the response of the North China Craton to global-scale geodynamic processes.

How to cite: Liu, G.: Detrital Zircon Records and Tectono-Sedimentary Evolution of the Mesoproterozoic Changcheng Period Strata in the Ordos Rift Zone, Western North China Craton, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8574, https://doi.org/10.5194/egusphere-egu26-8574, 2026.

EGU26-8574

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Flat Moho is a characteristic feature beneath extended continental lithosphere and orogenic plateaus; however, the physical processes that govern their formation remain poorly understood. In particular, the mechanical conditions required for lower crustal flow to effectively suppress Moho deflection are still debated. It has been proposed that lower crustal flow may facilitate lateral mass redistribution, thereby limiting Moho deflection and Moho relief during extension. Here, we compare seismological (receiver function) and gravity data and geodynamic models to identify the controls of Moho variation across various tectonic regions. Namely, we perform two suites of two-dimensional visco-plastic numerical models using the finite element code ASPECT with systematically vary (1) the minimum effective viscosity of the lower crust, and (2) its brittle strength, represented by cohesion. Each model simulates the extension of a 50 km-thick crust overlying a previously thinned lithospheric mantle, allowing us to isolate the rheological controls on Moho geometry and crustal deformation. Our results show that the primary factor governing Moho topography is the viscosity of the lower crust. When the lower crust is weak (≤ 10¹⁸ Pa·s), the viscous flow efficiently redistributes the material, leading to diffuse deformation and flat Moho (ΔMoho < 5 km). In contrast, high-viscosity models (≥ 10²¹ Pa·s) exhibit localized crustal thinning and pronounced Moho deflection, with relief up to 50 km and slopes exceeding 0.04 km/km. Varying the cohesion of the upper crust influences the distribution of brittle strain, but has a limited effect on Moho morphology. We conclude that flat Moho geometries arise from the integrated mechanical response of the crustal column where a sufficiently weak lower crust accommodates crust-mantle decoupling. These findings provide a quantitative framework to interpret observed flat Moho patterns in extensional settings such as the western Anatolia, the Basin and Range Province, and Tibetan Plateau.

How to cite: Bodur, Ö., Göğüş, O. H., Çavdar, E. N., and Çalınak, G.: Flat Moho beneath orogens and extensional regions: What controls it?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-979, https://doi.org/10.5194/egusphere-egu26-979, 2026.

EGU26-979

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Geodynamic modeling studies have shown that rift basin formation and their transition to sea floor spreading is controlled by tectonic deformation and surface processes. Furthermore, models are used to identify the controlling factors of symmetric vs asymmetric characteristics of the rift basins and the fault network patterns. Here, we use Black sea rift basin as a case study to test how varying model parameters can help to understand rapid subsidence and crustal stretching as well as up to 14 km of sediment thickness in the region. Namely,  we use high-resolution 2D geodynamic models (ASPECT) coupled with a landscape evolution code (FastScape) to investigate rift development under changing model parameters. We also reconcile model results against a number of geological and seismic reflection data where different types of stretching modes, such as pure vs simple have been described in the eastern and western sub basins. Our geodynamic model results provide important insight into how rifting has evolved in the black sea where thick sedimentary deposits are accumulated and possibly delayed continental break up.  That is, the thick sedimentary cover (Maykop) probably impeded serpentinization (sediment blanket) by modifying thermal structure of the crust. Models also explain the pure shear stretching (basin symmetry) in the eastern sub-basin compared to the west where migration of rift axis has been suggested and causing a broad zone of hyperextended crust.

How to cite: Tonguç, C., Göğüş, O. H., Bodur, Ö., Çavdar, E. N., Aslan, C., and Dinç Göğüş, Ö.: Factors controlling the rift basin formation in the Black sea region inferred from geodynamic models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18129, https://doi.org/10.5194/egusphere-egu26-18129, 2026.

EGU26-18129

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Continental rifting gives rise to margins with variable magmatic budgets, producing endmembers that range from magma-poor to magma-rich. At some magma-poor rifted margins like Australia-Antarctica conjugate margins and fossil margins seafloor preserved in Western Alps, portions of the lithospheric mantle were exhumed to the surface during the late phases of rifting. However, the key factors controlling this exhumation remain poorly constrained. From thermomechanical numerical scenarios, we investigated the controlling factors of the mantle exhumation process during rifting by varying crustal thickness, lithospheric mantle structure and rifting velocity. The results show that lower crustal strength and consequent lithospheric coupling drive the formation of exhumed mantle domains at magma-poor rifted margins. The exhumation process distributes different portions of lithospheric mantle along the rifted margins where at the most distal regions corresponding to initially deeper portions of lithospheric mantle. Factor as crustal thickness and mantle lithospheric structure affected the width of exhumed mantle domains. We observe that the stretching processes can exhume mantle particles from different lithospheric depths, sampling both shallow particles near the base of the crust and deeper portions of the lithosphere, especially in scenarios with an initially high degree of coupling between crust and lithospheric mantle. We also tracked the P-T-t paths of lithospheric mantle particles and our results agree with P-T-t paths from Iberian Margin, Diamantina Zone at SW Australian Margin and also from fossil rifted margins of the Western Tethys in the Alps and P-T estimation data for exhumed mantle samples from Newfoundland Margin and Terre Adélie seamount B at Antarctic Margin showing the potential of numerical models to explore the exhumation process in the context of magma-poor rifted margins.

How to cite: Macedo Silva, J. P., Sacek, V., Manatschal, G., and Ganade, C. E.: Reconstruction of exhumation history along magma-poor rifted margins - Insights from numerical models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-156, https://doi.org/10.5194/egusphere-egu26-156, 2026.

EGU26-156

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The complexity in the relationship between mantle and lithosphere processes may be most directly exemplified in the coupling between upwelling plumes and extending lithosphere at rifted margins, and the distribution of excess melting across these regions through space and time. Rifted margins are often described in two end-member classes; magma-rich and magma-poor, typified by the emplacement of seaward dipping reflector sequences (SDRs) and high velocity lower crustal bodies (HVLC) or the exhumation of serpentinised mantle with little extrusive melt, respectively. Previous studies have linked margin architecture and magmatic budget to extension velocity, lithosphere thickness, and rheology. The role of mantle plumes remains poorly constrained, with plumes associated with both magma-poor and magma-rich margins, implying that their influence on excess melt production is not straightforward. Our study aims to better constrain the relationship between mantle plumes and excess melting at rifted margins by exploring the interaction of plumes originating from the mantle transition zone and rifting.

We present two-dimensional numerical simulations to investigate how mantle plumes interact with lithosphere extension during continental rifting. Rifting is simulation using the ALE finite-element code FANTOM, incorporating a thermal anomaly at the base of the upper mantle to represent a stalled plume source. We systematically vary velocity, plume temperature anomaly, and plume position relative to the rift axis to explore how these parameters control the timing, magnitude, and spatial distribution of excess melting during breakup.

Our results indicate that excess melting associated with mantle plumes is both transient and spatially distributed. The timing, magnitude and lateral distribution of excess melting depends non-linearly on the interaction between plume buoyancy and lithospheric extension rate, with the strongest plume influence occurring at intermediate extension velocities. Plumes residing directly beneath the rift axis focus melt, producing temporally concentrated, focussed melt zones that promote earlier rift breakup whereas plumes which lie adjacent to the rift axis produce spatially offset and temporally delayed melt focussing, resulting in narrower but less efficiently coupled melt zones. These results demonstrate that plume-driven excess melting may be highly time-dependent with an evolving spatial distribution that reflects the efficiency of melt focussing relative to the thinning lithosphere.

How to cite: Plimmer, A., Huismans, R., and Wolf, S.: Controls on the spatio-temporal distribution of plume-related excess melting during continental rifting, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9953, https://doi.org/10.5194/egusphere-egu26-9953, 2026.

EGU26-9953

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What are the factors that control the generation and emplacement of magma during the rifting and breakup of continents? The Southeastern margin of Brazil along the South Atlantic Ocean offers an unprecedented opportunity to analyze this question. Here, the Tristan mantle plume appears to have exerted a significant influence on the magmatic processes associated with rifting. Yet, the influence of the plume on magmatism was spatially variable and heterogeneous along the margin. The basins south of the Rio Grande Fracture Zone (RGFZ) show clear evidence of magma-rich rifting, characterised by seaward-dipping reflectors and lower crustal magmatic intrusions emplaced during rifting. However, to the north of the RGFZ, the Santos and Campos Basins, generally lack the typical features of magma-rich margins. This asymmetric distribution of magmatism around the original plume head, differs from the classical view of plume-rift interaction which assumes that volcanism should be symmetrically distributed with respect to the plume head, as observed in the North Atlantic¹.

To unravel the geological controls on the spatio-temporal distribution of magmatism during rifting, we carried out a wide-angle seismic experiment across the transitional zone between the Santos and Pelotas basins in November 2025. This area has been well-imaged with deep commercial MCS imaging (e.g. [2]). However, information on the nature of the crust is currently lacking and questions persist on the compositional nature of the São Paulo plateau, which has been interpreted as either extended and potentially intruded continental crust (e.g. [3], [4]) or as an oceanic plateau⁵.

During cruise MSM141 on board the R/V Maria S. Merian we acquired three wide-angle lines overlapping with pre-existing ION-GXT multichannel seismic lines 150 and 140 across the margin and 220 across the RGFZ. In total, 126 stations were deployed at ~8.5 km spacing. Simultaneously, 29 onshore stations were deployed along a ~200-km-long transect aligned with line 150. These three-component broadband stations were spaced 5-10 km apart and operated continuously at 250 Hz for up to 42 days. During shooting, an airgun array with a total volume of 64 L (4,160 in3) was used as the seismic source. The seismic experiment aims to reveal how magmatism changed with distance from the RGFZ, and the crustal nature of the Abimael Ridge and of the São Paulo Plateau. Our specific goals are to understand the 3D kinematic history of the area, and the role of the preexisting lithospheric structure and the RGFZ in controlling the spatio-temporal distribution of magmatism. The project has been funded by DFG and Petrobras and will include seismic tomography of the wide angle data and numerical modelling of the opening of this area of the South Atlantic.

References

Morgan, J. P. et al. (2020). PNAS, 117(45), 27877-27883. doi:10.1073/pnas.2012246117

McDermott et al. (2019). EPSL, 521, 14-24. doi:10.1016/j.epsl.2019.05.049

Evain et al., 2015. JGR, v. 120, p. 5401–5431.

Araujo et al. (2022). Geol. Soc. Lon. Spec. Publ., 524(1). doi:10.1144/SP524-2021-123

Karner et al. 2021, in Marcio R. Mello, Pinar O. Yilmaz, and Barry J. Katz, eds., AAPG Memoir 124, p.215–256.

How to cite: Perez-Gussinye, M., Collier, J. S., Li, Y., Minshull, T., Duckworth, J., Nie, Y., Fontes, S., Alves, A., Neto, G., Grevemeyer, I., Araujo, M., Moulin, M., and Aslanian, D.: SOSEM, South Santos Seismic and modelling experiment: analyzing rift-plume interaction during break-up - Preliminary results., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13577, https://doi.org/10.5194/egusphere-egu26-13577, 2026.

EGU26-13577

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Continental rifting often induces decompression melting and the ascent of magma that intrudes into the brittle crust in the form of dikes and sills and that extrudes along volcanic fields. At the same time, continental rifts experience stress from topographic loading due to rift flank uplift. It is clear that these two processes interact in magmatic rifts such as the Kenya Rift, the Main Ethiopian Rift, the Afar triple junction, and at the Icelandic plate boundary. However, separating the interplay between tectonic and magmatic processes, the evolving topography and the rift-related stress field, as well as the impact of these processes on dike-fault interactions from field observations alone remains difficult.

Previous modeling studies of time-dependent magma-tectonic interactions in extensional tectonic settings generally fall into two categories: (1) Simple models (e.g. Buck et al., 2005) represent diking by a prescribed fixed rectangular zone of horizontal divergence. While this approach can be applied to model tens of millions of years of dike injection along spreading ridges, its simplicity prevents applications to continental rifts where magmatism manifests over broad areas. (2) More complex setups simulating magma ascent via porous flow and fluid-driven fracture (e.g., Li et al. 2023). This approach allows to study the evolution of individual dikes, but its computational costs prevent application to lithosphere-scale rifts over geological time scales. 

Here, we present a numerical workflow that can be categorized as a model of intermediate complexity. The dikes are nucleated at the brittle-ductile transition above zones of partial melt. They are then propagated perpendicular to the minimum compressive stress, similar to the approach of Maccaferri et al. (2014), until they reach their freezing depth or the surface. In this presentation, we show how we  approach this problem and how we implement it in the open-source community geodynamics model ASPECT. We demonstrate that the generated dikes are being focused in specific regions, and how the directional dilation and heat injection during magma intrusion through dikes influence the long-term rifting evolution. 

References:

Buck, W. Roger, Luc L. Lavier, and Alexei N. B. Poliakov. “Modes of Faulting at Mid-Ocean Ridges.” Nature 434, no. 7034 (April 2005): 719–23. https://doi.org/10.1038/nature03358.

Li, Yuan, Adina E Pusok, Timothy Davis, Dave A May, and Richard F Katz. “Continuum Approximation of Dyking with a Theory for Poro-Viscoelastic–Viscoplastic Deformation.” Geophysical Journal International 234, no. 3 (September 1, 2023): 2007–31. https://doi.org/10.1093/gji/ggad173.

Maccaferri, Francesco, Eleonora Rivalta, Derek Keir, and Valerio Acocella. “Off-Rift Volcanism in Rift Zones Determined by Crustal Unloading.” Nature Geoscience 7, no. 4 (April 2014): 297–300. https://doi.org/10.1038/ngeo2110.

How to cite: Fraters, M., Brune, S., Rivalta, E., Gassmöller, R., Liu, S., Muluneh, A. A., and Thieulot, C.: Intermediate-complexity modeling of magma–tectonic interaction in continental rifts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12670, https://doi.org/10.5194/egusphere-egu26-12670, 2026.

EGU26-12670

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The massive Orphan Basin, offshore Newfoundland, preserves evidence of a complex, multiphase rift history influenced by structural inheritance tied to the Appalachian-Caledonian orogen. Despite recent advances in plate kinematic reconstructions of the Southern North Atlantic, the tectonic evolution of the Orphan Basin remains poorly constrained, largely due to limited seismic and well coverage. As a result, the contributions of structural constraints on deformation have been oversimplified, leading to the misrepresentation of their influence on continental breakup.

This study prioritizes the interpretation of recently available 2D seismic reflection datasets acquired by TGS/PGS and ION Geophysical, developing stratigraphic and structural constraints to inform plate kinematic modelling. An analysis of the spatial distribution of Jurassic to Early Cretaceous syn-rift sediments and the geometries of major fault systems provide new insights into rift migration and the temporal variability of strain localization in the Orphan Basin during continental breakup.

Seismic interpretation and fault analysis identify two temporally distinct hyperextended rift basins separated by a region of thick crust, highlighting the importance of mechanically rigid blocks, such as the Orphan Knoll, in focusing strain, controlling basin development, and influencing the timing and geometry of rift propagation. While previous reconstructions have represented extension within the Orphan Basin as continuous and uniform, our analysis indicates that strain was instead focused within discrete extensional corridors controlled by large detachment faults.

Using GPlates, these seismic constraints are integrated into a deformable plate tectonic reconstruction, refining the kinematic plate model of the Southern North Atlantic while improving its geological accuracy and reducing the reliance on uniform crustal stretching assumptions. The updated reconstruction aims to provide a significant step towards a reproducible analogue model for hyperextended rift basins during magma-poor continental breakup. 

How to cite: Nickson, T. and Welford, J. K.: Integrating Seismic Interpretation of the Orphan Basin, Offshore Newfoundland, with Deformable Plate Tectonic Modelling of the Southern North Atlantic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3101, https://doi.org/10.5194/egusphere-egu26-3101, 2026.

EGU26-3101

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                Deciphering the dynamics of continental breakup is fundamental to understanding how oceanic basins initiate, segment, propagate and connect to the global oceanic system. However, constraining the spatial and temporal evolution of continental rupture is challenging as it precedes the establishment of continuous oceanic spreading and reliable kinematic markers such as marine magnetic anomalies. Here we focus on the earliest stage of Pangea breakup, with the aim of constraining basin segmentation during the initial opening of the Central Atlantic Ocean (CAO), prior to its connection with the main Panthalassa Ocean through the Western Tethys.

                The CAO corresponds to the earliest opened branch of the Atlantic.  The timing of its continental breakup and onset of oceanic spreading remains debated, with proposed breakup ages ranging from 195 Ma to 175 Ma. This uncertainty leads to major ambiguities in the geodynamic context of continental rupture, with consequences for the interpretation of rifted and nascent oceanic basins segmentation, connectivity, and associated depositional environments. It also affects the interpretation of major Jurassic magnetic anomalies identified across the CAO: the East Coast Magnetic Anomaly (ECMA) and Blake Spur Magnetic Anomaly (BSMA), which are commonly used as kinematic markers in early Atlantic reconstruction.

                To address these issues, we have compiled a regional database to integrate major rift structures and basins, Upper Triassic salt distribution, and variations in the nature of the ocean-continent-transition and magmatic type. We present interpretations of seismic reflection data along the Central Atlantic rifted margins, calibrated using available drilling results. These data allow us to constrain rift basin age and architecture, fault system development and the distribution of rift-related salt provinces. In parallel, regional crustal thickness maps derived from gravity inversion are used to investigate along-strike variations in magmatic budget during continental breakup and the early stages of oceanic accretion, relation with the spatial distribution of the ECMA and BSMA.

                Our first results confirm pronounced along-strike variations in magmatic volumes emplaced during continental breakup and the initial phases of oceanic spreading. The newly compiled database will provide key constraints for paleogeographic reconstructions, with the aim of clarifying the duration of oceanic basin isolation, the timing of basin connectivity through the Western Tethys and sedimentation pathways associated with the early Atlantic evolution.

How to cite: Heudes, B., Tugend, J., Mohn, G., and Kusznir, N.: Early opening of the Central Atlantic and its connection to the Western Tethys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10868, https://doi.org/10.5194/egusphere-egu26-10868, 2026.

EGU26-10868

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The Newfoundland rifted margin (NLRM) exhibits complex lithospheric features, including failed rifts, continental ribbons, transfer zones, and along-strike segmentation. Although the spatial variability of these tectonic features is central to understanding the region’s tectonic evolution, their interactions and broader implications remain debated. In this study, drawing on an unprecedented deep multichannel seismic dataset, we interpret a grid of margin-scale seismic reflection profiles to examine the variability of crustal necking and rift domain architectures along the NLRM and the associated Orphan Basin–Flemish Pass failed rift. Our interpretation reveals asymmetrical crustal necking on the conjugate sides of the failed rift, consistent with published numerical modelling studies, which suggest that asymmetric rifting is an early-stage process, potentially occurring before the necking phase. We observe more gradual crustal necking in regions of thinned and inferred weaker crust. In contrast, more abrupt crustal necking is associated with areas of thicker, inferred stronger crust, where transcrustal faults extending to depths greater than 20 km are imaged. Mantle serpentinization interpreted beneath both the NLRM and the failed rift zone indicates that serpentinization is not contingent on rift success or failure but is primarily governed by rheology and the availability of transcrustal faults. For magma-poor rifted margins, in contrast to magma-assisted rifting, transcrustal faulting linked with mantle serpentinization appears to facilitate continental breakup. Our systematic mapping reveals pronounced across-strike and along-strike variations in rift domain distributions, predominantly controlled by inherited transfer zones that segment the margin and that range from localized to diffuse, accommodating extension and giving rise to alternating strong and weak margin segments.  

How to cite: Alehegn, W. N. and Welford, J. K.: Nature of Crustal Necking and Rift Domain Architecture Along the Newfoundland Margin, Eastern Canada: Improved Seismic Perspectives and Interpretational Uncertainties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5349, https://doi.org/10.5194/egusphere-egu26-5349, 2026.

EGU26-5349

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Before Oligocene continental breakup at ~30 Ma, the South China Sea (SCS) lithosphere had an elevated geotherm following Cretaceous northward subduction of Pacific or Proto-SCS oceanic lithosphere under the continental South China block resulting in an Andean style orogeny and volcanic arc. We examine the consequences of this elevated geotherm on SCS crustal thickness determined from gravity inversion and determine the amount of lithosphere extension required for continental breakup and sea-floor spreading initiation.

Subsidence analysis of the northern SCS rifted margin shows up to 2 km subsidence of the base Oligocene unconformity to the present day that cannot be explained by observed extensional faulting and that we attribute to thermal subsidence from a very large pre-breakup lithosphere thermal perturbation. Parameterising the magnitude of this thermal perturbation by a McKenzie β factor requires a very large β factor > 4.

SCS crustal thickness predicted from gravity inversion incorporating an elevated pre-Oligocene lithosphere geotherm (GI model P3) is compared with that produced using an equilibrium initial lithosphere (GI model K1b). For very thinned continental crust and oceanic crust, GI models K1b and P3 give similar Moho depths that calibrate well against seismic reflection Moho depth. GI model K1b produces Moho depths consistently too deep (~ 5 km) for the northern SCS margin. In contrast GI model P3 with an elevated pre-rift geotherm produces Moho depths that calibrate well against seismic observations.

We examine profiles crossing the SCS to determine how much extension is required to stretch and thin continental lithosphere to generate continental breakup and initiate sea-floor spreading? Cumulative extension is calculated by integrating lithosphere thinning factor (1-1/β) determined by gravity inversion using GI model P3. Measured lithosphere extension prior to continental breakup and sea-floor spreading initiation in the SCS ranges between 303 km in the east and 558 km in the west predicted by GI model P3. In contrast measured lithosphere extension prior to rupture and separation of continental crust on the Iberia-Newfoundland conjugate rifted margins is 180 +/-20 km. Substantially more extension of continental crust (>200%) occurs before continental crustal breakup in the SCS compared with that between the Iberia and Newfoundland Atlantic margins

Our gravity inversion predicts a very wide region of continental crust with thicknesses between 25 and 10 km in the SCS, very much wider than for Atlantic type margins, due to a weak inherited SCS lithosphere rheology. The hot lithosphere geotherm prior to rifting and breakup gives a weak lithosphere rheology favouring extensional boudinage of the continental crust rather than crustal rupture and separation. Hot SCS lithosphere deformation contrasts with colder Atlantic Ocean type margins (e.g. Iberia-Newfoundland) where colder and stronger lithosphere rheology generates necking and focussing of lithosphere stretching and thinning.

How to cite: Kusznir, N., Taylor, B., Sapin, F., Zhang, C., Manatschal, G., and Chenin, P.: Consequences of Elevated Pre-Rift Lithosphere Geotherm on the Rifting and Breakup of the South China Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13499, https://doi.org/10.5194/egusphere-egu26-13499, 2026.

EGU26-13499

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We present a new first-approach methodology, applicable to thermally re-equilibrated rifted margins, to determine margin crustal architecture and magmatic type from the TWTT of top basement of time-domain seismic reflection data. The method invokes Warner’s 10s Moho rule (Warner, 1987) to give the TWTT crustal basement thickness from top basement TWTT from which we determine crustal basement thickness. It does not require the Moho to be seismically imaged or sediment thickness to be known.

Determining rifted margin crustal thickness and assessing whether a margin is magma-normal, magma-starved or magma-rich is fundamental to understanding margin structure and formation processes. This is often a difficult task compounded by the absence of clear or unambiguous seismic Moho.

Warner observed that, for a thermally re-equilibrated margin, the Moho seismic reflection is approximately flat at ~10s TWTT and is constant irrespective of the complexity of geology above. Moho TWTT is at 10s for unthinned continental crust, oceanic crust, and for crust in between, and applies equally to magma-rich, magma-starved and magma-normal rifted margins.

We apply the new methodology using Warner’s 10s Moho rule to map crustal basement thickness for the Campos and Santos rifted margins offshore Brazil from TWTT of top basement observed on seismic reflection data. We show that the resulting map of crustal thickness determined from top basement TWTT shows a good correlation with that determined using gravity inversion.

Modelling shows that different magmatic-margin types have distinct shapes of top basement TWTT that is independent of sediment thickness. The lateral transition from downward-sloping to flat top basement TWTT corresponds to the oceanward taper of thinned continental crust to boxed-shaped oceanic crust, providing an estimate of the landward-limit of oceanic crust (LaLOC). Magma-starved margins show a step-up of top basement TWTT onto oceanic crust. For margins with magma, lateral inflections in the TWTT of base sediment provide information of the onset of magmatic-volcanic addition and the formation of hybrid crust consisting of thinned continental crust plus new magmatic crust. For magma-normal margins this lateral inflections of TWTT corresponds to the start of deep-water volcanics (SDRs) at 6-7s TWTT. For magma-rich margins (with sub-aerially erupted volcanic SDRs) this TWTT inflection occurs at 2-3s.

We interpret the top basement TWTT profiles on the Southern Campos Margin to indicate a slightly magma-poor margin. The thinnest crust occurs between thinned continental crust and normal-thickness oceanic crust, consistent with a simple isostatic model where maximum decompression melting to form oceanic crust does not occur until after continental crust separation.

On the SW Santos Margin, we interpret the top basement TWTT profiles to indicate a slightly magma-rich margin. A broad region separates the end of the crustal thinning taper and the LaLOC. A simple isostatic model can generate this top basement TWTT shape as a broad region of hybrid crust or thicker-than-normal early oceanic crust.

Top basement TWTT cannot reliably identify the margin domain transition between the necking zone and hyperextended crust. This transition coincides with the onset of normal decompression melting and the start of hybrid crust.

How to cite: Graça, M., Kusznir, N., and Manatschal, G.: Rifted Margin Crustal Architecture and Magmatic Type from Time-Domain Seismic Reflection Data Using the Warner 10 second Moho TWTT Rule: A New First-Approach Methodology , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4961, https://doi.org/10.5194/egusphere-egu26-4961, 2026.

EGU26-4961

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The presence of pre- to early synrift salt leads to varying degrees of decoupling between supra- and subsalt deformation during rifting. Decoupling is favored by thick salt or small fault displacement. This has been examined in detail in low-𝛽settings such as the southern and central North Sea and is applicable to the proximal domains of rifted margins. In addition, the role of late syn-rift salt on margins has been extensively studied. But the behavior of pre- to early synrift salt in the high-𝛽 necking, hyperextended, and exhumed mantle domains remains poorly understood.

A common suprasalt geometry in the necking and hyperextended domains of the western Iberian margin is that of strata that dip and thicken basinward. These might be mistaken for growth strata adjacent to a landward-dipping fault bounding a horst or for salt evacuation structures in a half graben, with both interpretations invoking low-𝛽, high-angle normal faults. However, they more likely record extension associated with large-offset detachment faults, but with thickening onto the top of the hanging wall instead of the fault. Slip ceases on the low-angle, basinward-dipping fault between the hanging- and footwall cutoffs of the salt, with continued extension on the deeper part of the fault transferred to slip on the steeper, landward-dipping hanging-wall salt in a zig-zag pattern like that of fish-tail thrusts. This simple concept can guide interpretations in areas with inadequate imaging.

The same idea also explains the presence of significant volumes of pre- to early synrift salt in the exhumed mantle domain, as seen in the Mauléon Basin of the NW Pyrenees. This relationship is enigmatic because mantle represents new real estate that formed after salt deposition and, moreover, any salt should be highly attenuated. The solution is that as mantle is exhumed from beneath the upper plate, extension on the landward-dipping exhumation detachment is transferred to the basinward-dipping salt detachment on that upper plate, thereby generating a zig-zag fault geometry. Effectively, the upper plate moves out from between both detachments, which merge at the hanging-wall cutoff of the upper plate such that salt and suprasalt strata end up juxtaposed above the footwall of the exhumation detachment. That part of the detachment becomes locked and the salt above the mantle does not get attenuated by further extension.

How to cite: Rowan, M., Chenin, P., and Manatschal, G.: Using stratal geometries above prerift to early synrift salt to constrain crustal fault interpretations in the distal domains of magma-poor rifted margins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12780, https://doi.org/10.5194/egusphere-egu26-12780, 2026.

EGU26-12780

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The Mid-Norwegian margin and the North Sea rift are among the most extensively studied regions in the world, owing to their abundant geological and geophysical datasets. Their basement architecture is complex, having been shaped by the Silurian Caledonian orogeny and subsequent gravitational collapse during the Devonian. This was followed by multiple rifting episodes, separated by periods of tectonic quiescence. While the North Sea subsequently entered a post-rift phase dominated by thermal subsidence, rifting along the Mid-Norwegian margin persisted until continental breakup in the early Eocene.

Despite these studies, the mechanisms by which remnants of the Caledonian orogeny influenced later rifting stages remain unclear. For many years, seismic imaging could not penetrate to the depths required to investigate the complete basement architecture. Recent advances in seismic reflection imaging, however, have enabled the acquisition of long-offset, deep, high-resolution profiles extending up to 16 seconds two-way travel time (s-TWTT). The GeoexMCG Regional Deep Imaging (RDI) dataset thus provides an unprecedented opportunity to study the entire basement architecture, including the lower crust and lithospheric mantle.

This contribution summarizes the first results of a PhD study focused on a large-scale interpretation of the RDI dataset, supported by offshore-onshore geological correlations and gravity and magnetic modelling. Units with distinct seismic facies -i.e., zones of consistent reflectivity characterized by amplitude, frequency, and continuity - were defined in Petrel after multiple mapping iterations. Based on these results, the aim of the PhD study is to explore how inherited basement structures influence continental rifting and the formation of rifted margins at large scales.

How to cite: Castagné, C., Péron-Pinvidic, G., and Manatschal, G.: Basement Inheritance and Its Influence on Rift Evolution and Rifted Margin Architecture: The North Sea and Mid-Norwegian Margin., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7459, https://doi.org/10.5194/egusphere-egu26-7459, 2026.

EGU26-7459

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The structure of the Newfoundland–West Iberian conjugate margins has been extensively studied during the past 50 years in hundreds of papers. The crustal structure has been evaluated through seismic surveys and drilling expeditions, but those are not equally distributed in Iberia and Newfoundland. More work, and in particular recent studies on the West Iberian margin, have identified a complex crustal architecture characterised by continental, oceanic, and exhumed mantle domains that vary along the margin. This structural complexity has only been recently documented with modern data that allow to image the basement domains in detail.

In contrast, the Newfoundland basement remains comparatively less well understood due to a relative scarcity of seismic and drilling data. The main wide-angle and streamer data for this area, the SCREECH survey, were acquired in 2000 and modelled under the computational limitations of that time. The resulting models and images have been subject to debate and failed to unequivocally define the nature of the basement domains of the margins. This uncertainty has left open key questions regarding the evolution of deformation during rifting and, thus, also the degree of symmetry of this conjugate pair of margins.

The SCREECH acquisition parameters were similar to modern marine acquisition standards. We leveraged their inherent data quality with the current computational facilities and up-to-date methodologies to re-process the data, imaging the structure and modelling seismic phases. Recent advancements in parallel computing and novel geophysical techniques now allow for enhanced-resolution seismic models and a mathematically robust uncertainty analysis—tasks that were previously very computationally demanding.

Our study utilises the original SCREECH field data, consisting of three transects with coincident multichannel seismic (MCS) reflection data (6-km streamer) and wide-angle data recorded by short-period OBS and OBH stations at ~15 km spacing. By performing a joint inversion of the streamer and wide-angle data (utilising both reflection and refraction arrivals), we significantly improved the definition of geological units and the spatial resolution of the velocity models. A statistical uncertainty analysis was conducted to validate the reliability of these observed features.

Our findings reveal previously unrecognised crustal heterogeneity at the Newfoundland margin, including significant variations in thickness and composition along the margin. Notably, we challenge prior classifications of the crustal domains and the location and dimensions of the Continent-Ocean Transition (COT). Previous models identified an intra-basement deep reflector as the Moho, defining a 4–5 km thick layer interpreted as continental crust. However, our results suggest this reflector may not represent the Moho, as the observed crustal properties are inconsistent with typical continental or oceanic crust, and rather support a COT formed by >250 km of exhumed mantle. By integrating MCS imagery with these new velocity models, we provide a re-interpretation of the margin’s crustal structure and propose a refined evolutionary model for the West Iberian–Newfoundland conjugate system.

How to cite: Gómez de la Peña, L., R. Ranero, C., Prada, M., Merino, I., Shillington, D., and Sallarès, V.:  The Newfoundland margin crust: Understanding the Atlantic rifting., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14128, https://doi.org/10.5194/egusphere-egu26-14128, 2026.

EGU26-14128

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At continent–ocean transition zones (COTs) of magma-poor rifted margins, the basement is typically shaped by highs and large domes with variable elevation and spacing. These features expose large portions of serpentinized mantle, locally intruded by variable volumes of gabbroic bodies. In these environments, the mantle is exhumed to the seafloor through detachment faulting, which promotes deep hydrothermal fluid circulation and pervasive alteration. However, how hydrothermal processes, magmatic accretion, and detachment faulting interact and evolve over geological timescales remains poorly understood. We address this problem using a 2-D geodynamic model coupled with thermodynamic calculations of water–rock interactions. The model accounts for sedimentation, magmatic accretion, and hydrothermal processes. We focus on the well-documented magma-poor Iberia margin, one of the best documented COTs, supported by extensive geophysical data and deep drilling results. Our simulations reproduce the observed basement morphology through successive episodes of detachment faulting. We find, however, that the development of multiple detachments does not necessarily take place following a flip-flop mode, in which, alternately, oppositely dipping detachments sequentially cut through their predecessors. Instead, deformation may evolve through sequential non-flipping detachment faulting, where polarity remains constant. While the flip-flop mode leads to a geologically symmetrical architecture between conjugate margins, the sequential non-flipping mode results in an asymmetric lithosphere structure, characterized by larger volumes of gabbros on one conjugate margin. The development of one mode or the other depends on the depth at which magma is partitioned across the lithosphere axis and on how faulting redistributes accreted magma and weaker serpentinized mantle. Model predictions for both symmetric (flip-flop) and asymmetric (sequential non-flipping) deformation modes closely match observations, reproducing basement morphology, P-wave velocity (Vp) structure, and the petrological architecture consistent with geological IODP samples from Iberia. This suggests that, in magma-poor settings, first-order Vp variations within the oceanic crust primarily reflect alteration paragenesis and fault geometries rather than mafic-ultramafic distinctions. Consequently, alteration may mask underlying geological differences, with a potentially non-flipping detachment mode that leads to widely spaced domes of exhumed serpentinized mantle at COTs. The choice between these modes hinges on the long-term interplay of axial magma-partitioning, detachment faulting, and hydration processes.

How to cite: Merino, I. and Mezri, L.: Dynamics of detachment faulting at North Atlantic magma-poor rifted margins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19254, https://doi.org/10.5194/egusphere-egu26-19254, 2026.

EGU26-19254

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The Tyrrhenian Sea is a young back-arc basin that began to open in the Langhian/Serravallian (15.97-13.82 Ma). Its formation was driven by the eastward roll-back of the Apennine-Maghrebide subduction system, leading to the exhumation of the mantle in the Vavilov Basin. The spatio-temporal evolution of this exhumation occurred just after the Messinian Salinity Crisis (MSC). Consequently, the distribution and thickness of Messinian evaporites (5.97–5.33 Ma) provide a chronostratigraphic marker to constrain the transition from continental rifting to mantle exhumation. Within this framework, the present study aims to reconstruct a refined 3D Moho topography to reveal the relationship between crustal thinning and mantle exhumation.

In the Tyrrhenian Sea, we analysed a comprehensive suite of legacy seismic lines, including the SITHERE (1985), CS (1989), CROP (1995), and MEDOC and CHIANTI (2010 and 2015) surveys. We then converted Two-Way Travel time (TWT) into depth, integrating a robust velocity-depth model generated from five 2D seismic reflection profiles with coincident refraction data collected during the Spanish Survey MEDOC/CHIANTI. The resulting Moho geometry and the boundaries of mantle exhumation are validated and constrained by a synthesis of borehole data from DSDP, ODP (Sites 651 and 655), and the recent IODP Expedition 402 (Sites U1612, U1615, and U1616).

Our mapping reveals that a prominent, high-amplitude reflector is consistently observed across the region, typically occurring around 7s TWT. Once converted into depth, this interface deepens toward the continental margins and shallows toward the basin centres. In the Vavilov Basin, where mantle exhumation has been confirmed by drilling (U1614, U1616, and 651), we have identified reflectors within the exhumed basement. Notably, as imaged by the MEDOC-9 seismic profile crossing the heterogeneous exhumed domain at IODP Site U1612, one of these reflectors is sub-horizontal and truncates a set of rotated reflectors, suggesting a possible complex fault-like feature within the mantle.

The identified reflectors occurring within the mantle may be either a tectonic or hydrothermal boundary, such as a serpentinization front or a major detachment fault within the exhumed domains. Spatial correlations between Moho shallowing and the thinning of Messinian units indicate that the most intense phase of crustal thinning and mantle exhumation in the Vavilov Basin occurred shortly after the Messinian. Our new 3D Moho contour map provides a refined geodynamic framework for constraining the timing and magnitude of lithospheric extension in this back-arc region and for guiding future geodynamic modelling.   

How to cite: Yang, L., Prada, M., Ranero, C. R., Loreto, M. F., and Zitellini, N.: Mapping the Moho Geometry around the exhumated mantle in the Tyrrhenian Sea: A Synthesis of Multi-vintage Seismic Data and DSDP/ODP/IODP Drilling Results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13194, https://doi.org/10.5194/egusphere-egu26-13194, 2026.

EGU26-13194

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Observations at active magma-poor mid-oceanic ridges during ultraslow spreading (< 20 km/Myr full rate) are crucial for understanding the oceanization processes taking place during tectonic plate breakup. Particularly along magma-poor rifted margins, where subcontinental mantle is exhumed prior to the onset of oceanic spreading. It is hypothesized that this exhumation, occurring along detachment faults, is accompanied by a progressive increase in the magmatic budget, ultimately leading to the formation of a spreading ridge. These exhumation processes are believed to be similar to those observed in magma-poor areas along ultra-slow-spreading ridges, such as the easternmost part of the Southwest Indian Ridge (SWIR).

There, dredging revealed an oceanic basement composed of serpentinized exhumed mantle intruded by gabbros and locally overlain by variable amounts of basalts (Sauter et al., 2013). The morphology of the serpentinite ridges allowed to propose a "flip-flop" evolution of the detachment faults, characterized by alternating fault vergences. In this study, we analyse large-scale seismic reflection profiles of the Sismosmooth cruise (2014), over a series of peridotite ridges formed by flip-flop detachment processes. The absence of sedimentary cover allows for direct observation and ground-truthing of the nature of the exhumed basement at the seafloor (dredges, sub-marine images, bathymetry, TOBI side-scan sonar data). However, seismic reflection data are challenging to interpret due to the high impedance contrast between the water column and the basement, which limits wave penetration in the basement (Canales et al., 2004).

Our objective is to identify new criteria for identifying flip-flop detachment faults in contexts where the basement surface is covered by sediments, i.e. at continental margins. We also aim at identifying differences between flip-flop faulting at mid-ocean ridges and magma-poor rifted-margins. Detachment fault blocks in the easternmost SWIR form large amplitude, regularly spaced (11-18 km), mostly rounded and asymmetric ridges that expose serpentinized peridotites, locally with a thin basaltic cover. Seismic reflection data shows that the reflective top basement is locally affected by normal faults dipping mostly toward the ridge axis. Deep reflectors parallel to the top basement (~0.8 s TWT below top basement) occur locally, mostly beneath the inward-facing slopes of ridges, where the basement top is concave. We propose that they result from magma entrapment in the axial rift, when a new, antithetic, detachment fault cuts the previous one. Higher heat flow and hydrothermalism in the fault damage zone could prevent melt ascension to the seafloor.

We next look for these features (smooth reflective top basement ridges and reflectors ~0.8 s TWT below top basement) in seismic reflection profiles acquired across magma-poor rifted margins where flip-flop processes are suspected. We propose an interpretation of smooth basement ridges in the most distal magma-poor rifted margins as proto-oceanic or oceanic domains. We apply this approach to the Iberia and Antarctica fossil margins and show how this new criteria, allowing us to propose that flip-flop detachment processes took place during or directly after the final breakup of the lithospheric mantle, may help map and interpret key domains of the most distal part of magma-poor rifted margins.

How to cite: Autin, J., Sauter, D., Leroy, S., Cannat, M., and Cabiativa Pico, V.: Magma-poor spreading at the Southwest Indian ridge: new insights from multichannel seismic reflection data and implications for magma-poor rifted margins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13086, https://doi.org/10.5194/egusphere-egu26-13086, 2026.

EGU26-13086

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Located in the northern margin of the southern Okinawa Trough, the Mienhua Submarine Volcano (MSV) is probably formed during the post-collision of the former Taiwan orogeny. The MSV is accompanied by vigorous hydrothermal activities. To understand the related tectonic faults, volcanic intrusions, and hydrothermal activity of the MSV, we have collected several high-resolution sparker seismic profiles surrounding the MSV. Our results show that the east and west sides of the MSV show different features. In the east side, we have found unconformities, high-amplitude seismic reflectors, and acoustic blanking zones. The acoustic blanking zones indicate that hydrothermal fluid has penetrated the strata and migrated upwards and laterally. Many hydrothermal plumes are also found in the water column. In other words, hydrothermal activity is active in the eastern region. In contrast, in the west side of MSV, few unconformities or hydrothermal activities were found. Besides, large-scale mass-transport deposits (MTDs) are formed, possibly due to submarine landslides.

How to cite: Li, H.-W., Hsu, S.-K., Lin, L.-K., and Tsai, C.-H.: Geological structure related to the Mienhua Submarine Volcano in southern Okinawa Trough from High-Resolution Sparker Seismic profiles , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4342, https://doi.org/10.5194/egusphere-egu26-4342, 2026.

EGU26-4342

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Stretching of the crust, seafloor spreading, and volcanism commonly affect the overriding plate above retreating slabs in subduction settings. The Vavilov Basin (Tyrrhenian Sea) is a Pliocene–Quaternary back-arc basin formed in response to the eastward rollback of the Apennine–Tyrrhenian subduction system. The basin has a roughly triangular shape and it is bounded by major escarpments (e.g. the Selli Line) separating it from the continental margins (Cornaglia Terrace, De Marchi Seamount and Flavio Gioia Seamount). Its western sector is characterized by N–S–oriented ridges interpreted as the surface expression of basaltic magma injections during, or shortly after, mantle exhumation (e.g. the Gortani and the D’Ancona Ridges).

Near the centre of the basin, the Vavilov Volcano (VAV), a large volcanic edifice ~60 km long and ~32 km wide, rises from ~3600 m below sea level (b.s.l.) to a minimum depth of ~795 m b.s.l. The VAV consists of three main volcanic units: (i) west-tilted pillow lava flows below ~1500 m b.s.l., (ii) radial lava flows between ~1500 and 1000 m b.s.l., and (iii) scoriaceous lava flows from ~1000 m b.s.l. to the summit. K–Ar dating of pillow lavas sampled along the eastern flank at ~1000 m depth yields Pleistocene ages of 0.37 and 0.09 Ma, consistent with the observed magnetic pattern. Magnetic data show a positive anomaly over the shallow part of the volcano related to the Brunhes geomagnetic chron, and contrasting with negative anomalies on the outer flanks and surrounding basin.

Here we present an integrated magnetic and morphologic analysis of VAV aimed at constraining its internal plumbing system and the relationship with surface volcanic and tectonic structures. We develop an inverse magnetic model that images subsurface structural elements related to both an early spreading ridge and a later central volcanic system. Our results indicate that intervening intrusive ridges in small back-arc basins may evolve following a polyphasic evolution with a transition from fissural to central-type volcanism and developing a multi-level plumbing system. The VAV morphological asymmetry reflects an eastward migration of volcanic activity through time, possibly associated with asymmetric basin opening. The shallow plumbing system comprises: (a) an early NNE–SSW–elongated dike sheet feeding fissural volcanism along the summit ridge, and (b) a younger central magma reservoir beneath the summit feeding central vents. A NW–SE–oriented apophysis extending southeastward from the central reservoir likely supplied volcanic cones on the eastern flank.

How to cite: Cocchi, L., Muccini, F., Palmiotto, C., and Ventura, G.: Reconstructing the plumbing system of the Vavilov Seamount (southern Tyrrhenian Sea): insights into the transition from fissural to central-type volcanism back-arcs , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3400, https://doi.org/10.5194/egusphere-egu26-3400, 2026.

EGU26-3400

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In this presentation, we shall present results from studies of the Reykjanes Ridge (RR). RR is a continuous plate boundary extending some 1200 km from the Bight in the south to the north of Langjökull, Iceland. The boundary is oblique to the current plate motion. The RR has been mapped by multibeam techniques from the Bight fracture zone in the south to the Reykjanes peninsula. On land, however, the part of it that includes Reykjanes and extends to the Langjökull area in SW Iceland has been mapped by satellite techniques and photogrammetry. Thus, we have compiled all data for a morphometric study of its evolution. In this presentation, we shall focus on the past 1 Ma. The southernmost part of RR is characterised by a deep, well-defined rift valley, about 15 km wide, populated by en-echelon AVRs, extending to about 59° north. From there to Reykjanes (63.8° north), rift valleys are discontinuous and shallow, with densely populated and overlapping AVRs. On Reykjanes itself, the plate boundary becomes highly oblique, characterised by en-echelon fissures and AVRs, until it reaches the Hengill area (64° north). From Hengill to Langjökull (64.9° north), the system comprises shallow-to-deep rift valleys that widen to the north (13 → 30 km wide), with parallel AVRs. North of Langjökull, there is no clear evidence of RR continuation. The heading of different segments of the RR varies: from Bight to the Icelandic continental shelf at ~36°, on the continental shelf at ~50°, on the Reykjanes peninsula at ~65°, and from Hengill to its end at ~36°. At the same time, the spreading along the RR is at ~99°. The number of AVRs and thus magma production varies along the RR, being smallest in the south and increasing towards the north.

How to cite: Hoskuldsson, A., Martinez, F., Jónsdóttir, I., and Þordarson, Þ.: Current and past state of the Reykjanes ridge, from Bight to Langjökull SW Iceland. Magmatic and tectonic evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21605, https://doi.org/10.5194/egusphere-egu26-21605, 2026.

EGU26-21605

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