Magmatism and volcanism are fundamental components of all tectonic environments on Earth, and play a particularly crucial role in the evolution of magma-assisted continental rifting. Magmatism alters the rheological behaviour of the lithosphere by building networks of intrusions, thereby modifying how plates accommodate tectonic extension. The geochemical footprint of the eruptive products is affected by both the architecture of magma ascent pathways and by the timescales of magma storage and ascent. Volcanism, the surface manifestation of magmatism, results in the construction of large volcanic edifices or distributed volcanic fields. Volcanism is observed to shift during the lifetime of rift systems, eventually focusing on the rift axis in mature rifts. Surface eruptive vents are fed through complex magma plumbing systems, which we can observe through geophysical imaging.
Geodynamic modelling of the temporal evolution of lithospheric rheology and the magma evolution during ascent and storage demand for physics-based models of ascent pathways that incorporate the time scale of ascent and conditions for arrest. Such physics-based models would help better constrain the parameters of geodynamic codes by providing the tools to compare predicted magma pathways, magma evolution and distribution of volcanism with geological, geophysical and geochemical observations. However, this poses a challenge in linking the ductile deformation of the lithosphere and diking, which occur over vastly different spatial and temporal scales. The stress field has the dominant control on dike pathways and velocity: dikes open perpendicular to the axis of least compression to minimize work against the elastic stress field. Thus, an accurately calibrated stress field is fundamental for physically-consistent magma pathways. The stress field in the lithosphere evolves due to changing far-field stresses, new magmatic intrusions, growing surface loads, formation of basins, erosion and sedimentation; how can these be properly incorporated in geodynamic models? What rules do dikes follow when they propagate in a stressed medium? In this talk, I will present an evaluation of the dominant factors affecting the stress field, and propose guidelines for a physically consistent incorporation of magma pathways in geodynamic models.
How to cite: Rivalta, E.: Physically-consistent magma pathways in continental rifts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17843, https://doi.org/10.5194/egusphere-egu25-17843, 2025.
Dikes can contribute to rifting, but the space-time behavior and role of magma in young and slowly extending continental rifts is unclear. We use observations and modelling of InSAR and seismicity during the September to November 2024 Fentale intrusion in the Main Ethiopian rift (MER) to understand magma-assisted rifting at slow extension rates (5 mm/yr). From 2021 to mid-2024, the Fentale Volcanic Complex (FVC) uplifted up to 6 cm. From mid-September 2024, upper crustal diking started northwards along the rift, initially with subdued seismicity. From late-September to early November, dike opening increased to ~2m and propagated a total of ~14km north, causing increased seismicity from normal faulting. The dike made ~90% of the total geodetic moment, with the rest from faulting. The character of the event is similar to rifting episodes at mid-ocean ridges and demonstrates that episodic diking can occur in young, slow extending continent rifts but must be more infrequent. This marks the start of a major rifting episode.
How to cite: Keir, D., La Rosa, A., Pagli, C., Wang, H., Ayele, A., Lewi, E., Monterroso, F., and Raggiunti, M.: The September to November 2024 Fentale dike in the Ethiopian rift, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3968, https://doi.org/10.5194/egusphere-egu25-3968, 2025.
The arrival of upwellings within the mantle from Earths deep interior are commonly observed worldwide, but their role in driving volcanism during continental breakup has long been debated. Given that only a small fraction of Earth’s upwellings are situated under continents and a limited number of them are associated with active continental rifting, our understanding of these processes remains incomplete.
Here, we investigate the interplay between continental breakup and mantle upwellings using the classic magma-rich continental rifting case study of the Afar triple junction in East Africa. Some studies previously proposed that the region is underlain by mantle upwelling(s), yet others argue for limited involvement of mantle plumes. Several discrete segments of the rift have been studied in terms of magma petrogenesis. However, until now, a paucity of high-precision geochemical data across the broader region has hampered our ability to test the models and evaluate the spatial characteristics and structure of this upwelling in the recent geologic past.
Within this study, we present extensive new geochemical and isotopic data spanning the region and integrate these with existing geochemical and geophysical datasets shedding light on the spatial characteristics of the mantle beneath Afar. By combining geophysics and geochemistry using statistical approaches, our multi-disciplinary approach shows that Afar is underlain by a single, asymmetric heterogeneous mantle upwelling. Our findings not only validate the heterogeneous characteristics of mantle upwellings, but demonstrates their susceptibility to the dynamics of the overriding plates. This integrated approach yields valuable insights into the spatial complexity of mantle upwellings.
How to cite: Watts, E. J., Rees, R., Jonathan, P., Keir, D., Taylor, R. N., Siegburg, M., Chambers, E. L., Pagli, C., Cooper, M. J., Michalik, A., Milton, J. A., Hinks, T. K., Gebru, E. F., Ayele, A., Abebe, B., and Gernon, T. M.: Afar triple junction fed by single asymmetric mantle upwelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6181, https://doi.org/10.5194/egusphere-egu25-6181, 2025.
A quadruple junction is a distinctive phenomenon in plate tectonics characterized by the convergence of four tectonic plate boundaries at a single geographic location. While such occurrences are infrequent within the realm of plate tectonics, they provide a valuable opportunity to explore the processes involved in the evolution of the solid Earth. In this context, we examine the Afro-Arabia plate boundary as a pertinent example of a quadruple junction. The establishment of the Makkah Madinah Transform Zone (MMTZ) as a significant tectonic boundary has profoundly influenced the geological framework of western Arabia, offering a fresh perspective on the geodynamics of the broader Red Sea area, particularly with the advent of the central Red Sea triple junction. The MMTZ is estimated to have an age ranging from 27 to 30 million years, inferred from the configuration of plate boundaries surrounding the southern Red Sea, Sirhan, eastern Mediterranean, and the Zagros orogenic zone. In our reconstruction of the Red Sea, we apply a rotation of 6.7 degrees for Arabia relative to Africa, utilizing the topographic alignment of both rift flanks to facilitate basin closure. We establish a connection between the MMTZ plate boundary and the Ader Ribad depression in Sudan, grounded in both spatial and temporal analyses. Chronological investigations of the Ader Ribad depression indicate an exhumation event occurring approximately 31 million years ago, coinciding with the timeline of the MMTZ. The coexistence of these two plate boundaries exemplifies a unique tectonic scenario of a quadruple junction. We present reconstructions of the Afro-Arabia plate and 3D thermo-mechanical numerical models with the code I3ELVIS of the Afro-Arabia plate boundary to substantiate our hypothesis. The code implements a marker-in-cell approach with finite differences method. The model consists of upper and lower continental crust, lithospheric and sublithospheric mantle until 220 km depth. Multi-directional extension is simulated by imposing variable divergence velocities on the right and rear model sides. Extensional and transtensional deformation is initially localized along implemented rheological and thermal weaknesses.
How to cite: Aldaajani, T., Attila, B., Gerya, T., Ball, P., Almalki, K., and Abd El-Motaal, E.: Evolution of Quadruple Junction: Example from Afro-Arabia plate boundary, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14789, https://doi.org/10.5194/egusphere-egu25-14789, 2025.
The Afar region provides a rare onshore glimpse into the dynamic processes of magmatic continental rifting and the progression towards continental break-up. This area features multiple active magmatic segments distinguished by varied morphologies, crustal thicknesses, rates of magma production, and magmatic-tectonic styles. In the Erta Ale Range rift segment, extension is accommodated magmatically, making it an ideal location to study the magmatic behavior of a mature rift segment. The Erta Ale Range includes sub-segments with magma compositions ranging from basalts to rhyolites, but only the Erta Ale Volcano (EAV) sub-segment is currently active, where only basaltic compositions have been reported so far. Our analyses of major and trace elements, along with isotopic studies of olivine crystals, interstitial glasses, and melt inclusions, combined with oxy-thermo-barometry and thermodynamic modeling, delineate the evolution of magma beneath EAV. We reveal extensive in-situ fractional crystallization within a shallow magmatic reservoir, evidenced by unique cognate gabbroic and microgabbroic blocks. These cognate samples uncover previously unknown mushy and evolved parts (up to 75 wt.% SiO2) of the EAV plumbing system. These findings highlight a sophisticated, transcrustal magmatic plumbing system that contrasts with typical oceanic rift systems, indicating a transitional phase in rift evolution. Our results suggest a magmatic plumbing system that extends up to 12 km in depth, accommodating the rift's extensional dynamics through both magmatic differentiation and tectonic processes. This system is indicative of a rift in an advanced stage of development yet not fully matured to oceanic spreading. Our findings contribute to refining the conceptual models of rift evolution by providing detailed insights into the magmatic and tectonic processes at a critical junction of the Afar rift system. The study emphasizes the complex nature of magmatic systems during the transitional phases of break-up and highlights the need for reconsidering the criteria used to determine the stages of continental break-up. We discuss this model within the geological contexts of the Erta Ale Range rift segment and the larger Afar region, and highlight contrasts with mature oceanic systems to argue that the region is not in the final stages of continental break-up.
Pin, Chazot, France, Abily, Gurenko, Bertrand, Loppin, 2024. Protracted magma evolution and transcrustal magmatic plumbing system architecture at Erta Ale volcano (Afar, Ethiopia). Journal of Petrology 65, egae118. https://doi.org/10.1093/petrology/egae118
How to cite: Pin, J., Chazot, G., France, L., Abily, B., Gurenko, A., Bertrand, H., and Loppin, A.: The magmatic plumbing systems during the continent-ocean transition: the example of the Erta Ale rift, in Afar, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2549, https://doi.org/10.5194/egusphere-egu25-2549, 2025.
Northeastern Oman is located near a Late Paleozoic rift-rift-rift triple junction as part of the Pangea breakup. Above a major and plate-wide unconformity (“basal Saiq Unconformity” or “Hercynian Unconformity”), Late Permian shelf carbonates deposited in much of Arabia and northeastern Oman. In the southeastern Saih Hatat area of NE Oman, near Quriyat, a ~10-100-m-thick conglomerate to sandstone siliciclastic unit (basal Saiq) is sandwiched between the unconformity and the carbonates. We investigated 519 detrital zircons from 7 samples of different intervals within the ~80 m thick basal Saiq. The composite age distribution depicts Archean (2.998±0.007 Ga) to early Mesozoic ages (248±3 Ma). Minor age peaks are at ~2.3-2.6 Ga and 1.6-1.9 Ga. The majority of detrital zircons yield a Neoproterozoic to Paleozoic age (~0.3-1.0 Ga), with most of the ages between ~0.7-0.8 Ga. One sample from the middle part of the section contains zircon grains with a major age distribution of ~300-500 Ma and a peak at ~460-480 Ma. The same sample and a further sample from the lower part of the section contains a significant amount of zircon grains with ages at ~330-350 Ma. The youngest measured ages of 248±3 and 254±3 Ma are detected from two grains of two samples.
Our Precambrian detrital age distribution pattern is similar to patterns known from NW India and eastern Oman (comp. Gomez-Perez & Morton, in press). The Archean and Mesoproterozoic ages likely to have a Neoproterozoic Indian origin. Tonian to Cryogenian ages are the dominant ages, reflect crustal growth of the Omani crystalline basement, with identical U-Pb zircon ages from igneous basement rocks and with flysch-type rocks, formed in the surroundings of a volcanic arc outcropping at the surface in northeastern Oman (Bauer et al., 2025). Infra-Cambrian ages were produced during the final closure of the Mozambique Ocean, as part of the Angudan Orogeny (Gomez-Perez & Morton, in press). Ordovician ages of two samples reflect a regional to local alkaline magmatic event related to continental rifting. Abundant lower to mid-Carboniferous zircon ages (~330-350 Ma) within two samples documents for the first time that the Hercynian event in Oman produced magmatic rocks, beside known rock tilting. Finally, two Permian/Triassic zircon grains ages are derived from volcanic rocks during the Pangea rifting, overlapping in age with the depositional ages of the shallow-marine carbonate of the Saiq Formation. This suggests that the Pangea rifting produced minor acidic igneous rocks in NE Oman.
References
Bauer, W., Jacobs, J., Callegari, I., Scharf, A., Schmidt, J., Mattern, F., 2025. New constraints on the Neoproterozoic geological evolution of the SE corner of the Arabian Plate (NE Oman). In: Scharf, A., Al-Kindi, M. and Racey, A. (eds.) Geology, Tectonics and Natural Resources of Arabia and its Surroundings. Geological Society, London, Special Publication, 550(1), 49.
Gomez-Perez, I. & Morton, A. 2025. Neoproterozoic-Early Paleozoic tectonic evolution of Oman revisited: implications for the consolidation of Gondwana. In: Scharf, A., Al-Kindi, M. and Racey, A. (eds.) Geology, Tectonics and Natural Resources of Arabia and its Surroundings. Geological Society, London, Special Publications, 550(1).
How to cite: Scharf, A., Qasim, M., Callegari, I., and Bauer, W.: Detrital zircon U-Pb geochronology of the basal Saiq siliclastics – A complete magmatic record from the Archean to the Permian/Triassic of NE Sultanate of Oman, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3424, https://doi.org/10.5194/egusphere-egu25-3424, 2025.
We use a newly developed model formulation to explore the potential structural evolution of a spectrum of margins from Volcanic to Magma-poor. We assume that the melt is incompressible, and we simulate melt migration as magmatic intrusions and volcanic extrusions as volume change and stress change in the brittle and ductile crust. We also model heat transfer generated by melt migration, latent heat of recrystallization, melt production and hydrothermal circulation.
Based on our simulation and observations of passive margins, we propose models for the formation of volcanic and magma-poor margins. While magma-poor margins evolution follows well-known stages, we show that volcanic margins represent a wide spectrum of behavior from purely accretionary and volcanic to mixed extensional and volcanic. The nature and extent of seaward dipping reflectors (SDRs), the crustal composition and structure, the subsidence of the margins vary as a function of the mantle potential temperature in the asthenosphere and the initial geothermal signature of the lithosphere.
We can resume our main findings which diverge strongly from existing models for volcanic margins: (1) For mantle potential temperatures (Tp) greater than 1400oC, we find that volcanic margins form through the accretion of intrusive magmatic and extrusive volcanic product of melt production in the asthenosphere. This system forms an accretionary center of thickness and width increasing with Tp. On both side of the accretionary axis, two symmetrical SDRs basins form. Subsidence of these basins increase with decreasing Tp. Increasing subsidence generated by far field extension leads to an increase in clastic sedimentation and controls SDRs composition. Decreasing Tp and increased subsidence leads to the formation of clastic rich SDRs while increasing Tp and decreased subsidence leads to formation of mainly volcanic/mafic SDRs. (2) The exhaustion of melt production leads to ridge jumps and the formation of eccentric accretionary center. When subsidence is more pronounced for a lower Tp we simulate periods of uplift and subsidence correlated with periods of higher and subdued melt production, respectively. This process may result in cyclical periods of mafic followed by clastic sedimentation. (3) For Tp lower than 1400oC, intermediate margins form with both volcanic and extensional processes occurring concurrently. This processes eventually lead to the asymmetric propagation of volcanic centers which may lead to seafloor spreading.
How to cite: Lavier, L.: Magma-poor To Volcanic Margins: New Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14609, https://doi.org/10.5194/egusphere-egu25-14609, 2025.
Continental rifts and rifted margins are governed by the complex interplay of a range of factors: thermo-mechanical processes control deformation at depth modulated by the emplacement of melt, while erosion and sedimentation reshape surface topography. Understanding the intricate links between geodynamic, magmatic and surface processes is essential to unravelling how rifts evolve, how they interact with the Earth system and under which conditions georesources are generated.
This presentation highlights latest technical advances and insights into the interaction of rift processes. It uses a recently established framework in which the open-source geodynamic software ASPECT is bi-directionally coupled to the landscape evolution code FastScape. This approach captures the dynamic interaction between faulting, surface loading, isostasy, rift-shoulder erosion and intra-basin sedimentation from rift initiation to rifted margin formation. In addition, dikes are incorporated via a one-way coupling scheme using two approaches: (1) a post-processing technique that infers potential diking pathways based on the modelled tectonic stress field, or (2) via user-defined input where dikes are represented as thin vertical domains with prescribed horizontal dilation.
These models reproduce the common finding that melts often rise sub-vertically to the surface in the form of dikes. However, compressional domains associated with block rotation are surprisingly common features in our models that result in the deflection of ascending melt. This process could explain the formation of sills in sedimentary basins and basement rocks, as well as the horizontal offset between melting zones in crust and mantle: features observed in several magmatic rifts. Our models suggest a complex interaction between diking, faulting, and sedimentation, which are compared to selected regions in the eastern branch of the East African Rift. These results illustrate how advances in numerical modelling techniques, combined with multidisciplinary field data can lead to new insights into the process interactions that control the structure and evolution of individual rift segments.
How to cite: Brune, S.: Process interactions in continental rifts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13571, https://doi.org/10.5194/egusphere-egu25-13571, 2025.
Numerical models are essential tools for investigating a variety of Earth phenomena, providing insights into the role of different surface to deep Earth processes. As with many laboratory approaches the effectiveness of the models can be assessed by comparing their results with natural case studies of the same phenomenon, which helps to constrain the large number of model parameters.
This presentation will take the example of the Pannonian Basin system having been formed within the Alpine–Carpathian–Dinaric orogenic belt, where geological data are abundant, and the temporal resolution of basin evolution including magmatic events are very good and in the range of the numerical modelling results.
We used 3D coupled thermo-mechanical and surface processes numerical models (I3ELVIS-FDSPM code) to simulate continental rifting and to shed light on the temporal evolution of the entire rift system. Namely, the extensional deformation starts than migrates from the (western) basin margins, from inherited lithospheric weakness zones towards the basin centre, but an early jump from the western margin toward the opposite basin part is also present in some experiments. This is followed by a second jump of basin formation toward the basin centre, between the first and second generations of basins. This is in good agreement with the compilation of the ages for the onset of basin subsidence and migration of activity of some major bounding faults including low-angle detachments of metamorphic core complexes. This migration is driven and supported by mantle flow and asthenospheric upwelling, eventually affected by thermal relaxation. Based on detailed geological and geophysical mapping, we point out the role of inherited weakness zone(s) – mostly former suture zones – within the crust and mantle lithosphere. Consequences are contrasting subsidence and uplift patterns and a variable heat flow evolution in different sub-basins.
The migration of basin formation shows remarkably similar migration of the magmatic activity. This started with granodioritic–dacitic products around 18.6 Ma along the western basin margin, then jumped toward the opposite basin part around 17.3–16.8 Ma and stepped back toward the basin centre around 15.3 Ma with a change toward andesitic volcanism. Geochemical characteristics indicate increasing mantle component in the melts during the continuing extension until ca. 14.4 Ma. The magma generation in the lower crust and mantle (by decompressional melting) is predicted by numerical models.
The evolution of basin formation and magmatism between ~14.9 and ~11.5 Ma is marked by the migration from the basin centre toward the eastern margin and is probably due to subduction roll-back, steepening of the slab and its detachment. This process is combined with self-consistent evolution of mantle processes deriving from the rifting of the overriding lithosphere.
The research was supported by the National Research, Development and Innovation Office project number K134873 granted to László Fodor and no. 145905 granted to Réka Lukács and MTA–HUN-REN CSFK Lendület "Momentum" PannonianVolcano Research Group
How to cite: Fodor, L., Balázs, A., Oravecz, É., Harangi, S., Cloetingh, S. A. P. L., Gerya, T., and Lukács, R.: Migration of deformation, basin subsidence, magmatism in extensional basins: comparative constraints from numerical models and observations (Pannonian Basin), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16095, https://doi.org/10.5194/egusphere-egu25-16095, 2025.
The European Cenozoic Rift Intraplate System (ECRIS) is a deep crustal discontinuity. On the surface, its longest segment, the Rhine Basin, is a large scale asymmetric rift that has been largely studied by sedimentary and tectonic inquiries for its oil and geothermal potential. However, the mechanism behind its development is still under discussion. Different scenarios co-exist, among them an East-West Oligocene extension of unknown origin (Bergerat, 1985), a transtensive opening, associated with a North-South compression linked to the Pyrenean orogeny (Bourgeois et al., 2007) and an opening caused by the alpine slap pull (Merle and Michon, 2001).
This study focuses on the reinterpretation of 1500km of seismic lines and 330 boreholes in the Rhine Graben French part. Four evolutive isochrones and structural maps are proposed, showing the evolution of the fault activity and sedimentary deposition during the Cenozoic. They have been constructed through a seismic stratigraphy analysis that allowed to map five stratigraphic interpolated horizons within the Cenozoic sedimentary pile, including a newly interpolated intra-Chattian horizon. Furthermore, the 3D fault networks active during each period have been constructed, sorting the faults regarding their periods of activity and correlating their expression from one seismic profile to another, including their geometry, their measured throw values, and impact on the sedimentary filling of the Graben.
The first isochrone/structural map extends from the Lutetian to the end of Priabonian (Eocene), lasting 10Ma. It displays a North-South succession of small basins constrained by NS to N40° faults, except in the Erstein transfer zone, where a N70° Variscan suture marks the bedrock. Here, faults adopt a N150° trend. The major West border faults are segmented, alternating with onlap zones.
The second map is of Rupelian (Oligocene) age, lasting 2.9Ma. It displays three larger basins, the Strasbourg, Selestat and the Dannemarie basins, separated by EW thresholds of lower subsidence. In those basins, the three time faster subsidence indicate the climax of the rifting. Interestingly, intra-basin active faults are less numerous during this step and are only reactivated faults from the first step.
The third map points to a transition phase of Rupelian-Chattian age (Oligocene) lasting 4.4Ma. It is characterized by a global slowing down of the subsidence and the tectonic activity except for a small basin at the North-Eastern limit of our study area, constrained by a N10 fault.
The last map is of Chattian to Late Miocene age, lasting 21.1Ma. It is characterized by a new high subsidence in the North, lasting from Chattian to mid-Miocene, but also by the re-activation of the former faults and the development of newly formed normal or transtensive faults. This extensive event is followed by a transtpressive event (supposedly Late Miocene) illustrated by faults-flanked anticlines structures, interpreted as positive flower structures linked to the Alpine orogeny.
This study points to the complex structure of the Rhine basin, involving several sub-basins and fault kinematics evolving in space and time, and the major role of deep structural inheritances in governing the graben asymmetry and fault expression in the sedimentary cover.
How to cite: Ourliac, C., Homberg, C., Briais, J., Allanic, C., Schueller, S., Verlaguet, A., and Faure, A.: Deconvoluted evolution of the intra-plate Rhine Graben during the Cenozoic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15994, https://doi.org/10.5194/egusphere-egu25-15994, 2025.
Continental passive margins are often defined by early salt-related rift systems buried beneath thick sedimentary successions, with structural and sedimentary architectures only directly observable when inverted in orogenic systems where primary salt structures are overprinted by compression. The Central High Atlas diapiric province (Morocco) is an inverted salt-related rift basin with active salt tectonics since early Mesozoic times that provides an exceptional view of early syn-rift sediments and structure. For the first time, regional balanced and restored cross-sections of the Central High Atlas showing the diapiric nature of the basin and the role of salt tectonics during its evolution are presented. The constructed cross-sections across the Central High Atlas include seven salt walls and six intervening elongated minibasins with associated halokinetic depositional sequences, providing evidence of diachronous diapiric growth from Early Jurassic to Cenozoic times. Several of these diapirs bifurcate or amalgamate along strike, so the number of major structures varies laterally. The comparison of the restored and balanced cross-sections allows estimating a shortening of about 38 km, 21 km accumulated in the Atlassic fold and thrust belt frontal domains, and 17 within the Jurassic rift basin.
During the Early Jurassic rifting, shallow water carbonate platforms nucleated both along the margins of the High Atlas Basin and around most salt walls (i.e., highs) within the basin, while intervening minibasins underwent higher subsidence rates and were filled with deeper-water limestones and marls. Subsequently, a longitudinal mixed clastic carbonate deltaic system prograded eastwards filling the minibasins between the long rising salt walls. During this stage, shallow marine shoals and reef patches developed attached to the diapiric walls, evidencing continuous diapir rise.
Throughout the whole rift basin, where local diapir uplift rate is similar to regional subsidence rate, shallow deposition environments or even local subaerial conditions occurred. Thus, platform development was enhanced and karstic processes could develop around salt structures in central parts of the basin. The lessons learnt in the Central High Atlas serve as a valuable analog and provide insights for understanding the early stages of rifting, salt tectonics, and the subsequent evolution of passive margins on a worldwide scale.
How to cite: Moragas, M., Saura, E., Martín-Martín, J. D., Vergés, J., Razin, P., Grélaud, C., Messager, G., and Hunt, D.: The Central High Atlas Jurassic diapiric province (Morocco): a field analogue for salt rift basins preceding continental break-up, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17309, https://doi.org/10.5194/egusphere-egu25-17309, 2025.
As the front edge of the continental collision zone, the Indo-Eurasian continental collision belt has great significance for studying the plate collision process, plateau uplifting mechanism and orogenic activities within the plateau. Several models have been proposed to explain north-south compression collision and east-west extension based on geological and geophysical observations. Among them, the distance and shape of subducted India's lower crust and its geometry under the southern Tibet rift are still controversial. To address these issues, we analyze arrival times of P- and S-wave from 35,193 local and regional earthquakes recorded by 575 permanent and temporary stations, and apply an improved double-difference tomography method to obtain high-resolution 3-D P- and S-wave velocity structures of the crust and upper mantle and the locations of the relocated events in the Indo-Eurasian continental collision zone. The east-west velocity profiles reveal that there exists a discrete high-velocity layer dipping eastward at depths of 40-60 km beneath the Longgar rift (LGR), Tingri-Nyima rift (TNR), Xianza-Dinggye rift (XDR), and Yadong-Gulu rift (YGR), which suggests that the subducted Indian lower crust had experienced tearing. On the basis of comprehensive analysis about seismicity, source mechanism of large earthquake in the mantle, and tomographic images, we propose a new dynamic model to present India-Eurasia collision and North-South rifts formation. The significant character of this model is that, the rifts do not cut through the crust vertically but obliquely.
How to cite: Pei, S. and Li, J.: Oblique Rifting in the Southern Tibetan Plateau Revealed From 3‐D High‐Resolution Seismic Travel‐Time Tomography Around the India–Eurasia Continental Collision Zone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1935, https://doi.org/10.5194/egusphere-egu25-1935, 2025.
Post-cratonization rifting has emerged as a prominent research focus in structural geology due to its association with significant hydrocarbon accumulations. Such rift systems are extensively developed within and along the margins of cratonic regions during the Mesoproterozoic to Neoproterozoic, notably in areas such as the Siberian Craton, Australian Craton, and North American Craton. The genesis of these rift systems is typically attributed to extensional tectonic regimes that evolved during the post-orogenic reconfiguration of cratonic lithosphere. These systems represent critical tectono-sedimentary processes that influence crustal thinning, fault block development, and the formation of accommodation space, playing a key role in hydrocarbon source rock maturation, reservoir development, and trap formation. Recent advancements in natural gas exploration within the Ediacaran strata of the Sichuan Basin have revealed the substantial hydrocarbon resource potential of the Neoproterozoic sequences in the Upper Yangtze Craton. These exploration successes are intimately associated with the development of deep-seated extensional rift systems in the Yangtze Craton, which are interpreted as the result of rapid lithospheric extension following cratonization during the early Neoproterozoic. Despite these breakthroughs, a comprehensive understanding of the structural geometry, kinematic evolution, and petroleum systems of these rift systems remains limited, highlighting the need for further systematic investigation. This study integrates two-dimensional and three-dimensional seismic data with magnetotelluric data, deep borehole records, and field outcrop observations to construct, for the first time, a three-dimensional structural model of the Neoproterozoic rift systems in southwestern Sichuan Basin. The results reveal two distinct rifting phases during the Early to Middle Neoproterozoic, with rift dimensions ranging from 3-8 km in width and 7-23 km in length. The rift systems and associated fault networks predominantly display NE and NNE trends, with faults generally dipping northwestward. These faults governed the development of half-grabens during both rift phases, each accompanied by sedimentary deposits reaching thicknesses of 2–3 km. The stratigraphic sequences within the rifts exhibit strong correlations with the Neoproterozoic strata exposed along the western margin of the Yangtze Craton. Chronological evidence indicates that the first rift phase (800–720 Ma) was characterized by independently developed sub-rift basins. The second rift phase (720–635 Ma) inherited and expanded upon the earlier rifting, culminating in the development of a unified, large-scale half-graben that overlies the sub-rifts of the first phase. During the late syn-rift stage, significant compressional uplift along the western Yangtze Craton margin induced structural inversion of several pre-existing rift normal faults in southwestern Sichuan and the formation of pre-Ediacaran reverse faults. This compressional event eroded over 3 km of rift-related sequences. The Neoproterozoic rifting and subsequent compressional deformation along the western Yangtze Craton margin are closely tied to subduction and rollback dynamics of the Pan-Oceanic plate. This study emphasizes the excellent conditions for hydrocarbon source rock and reservoir formation in the Neoproterozoic of southwestern Sichuan, highlighting its vast potential as a target for future hydrocarbon exploration.
How to cite: Lu, G. and He, D.: 3D Structure, Evolution, and Geodynamic Model of the Neoproterozoic Rift Basins in Southwestern Sichuan Basin, South China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7068, https://doi.org/10.5194/egusphere-egu25-7068, 2025.
As one of the largest marginal seas in the Western Pacific, the structure and evolution of the South China Sea will provide important reference to the marginal sea research. In order to decode the continent-ocean transition and seafloor spreading process of the South China Sea, 3 normal and 1 extended IODP drilling expeditions were carried out from distal margin to the relict ridge of the South China Sea. However, large controversies still exist due to the lack of enough drill site-coordinated geophysical investigation to calibrate the drilling results. 30 active source OBSs were deployed along the 300 km long drilling transect and then a 3D network with 60 OBSs were deployed in the Continent-Ocean transition zone. The velocity models deduced from the OBSs suggest that thick and widespread magmatic underplating occurred below the northern continental margin, with the thickest underplating occurred below the continental slope where the crustal thickness is over 20 km. Correlated with the sedimentary history, the strong magmatic underplating is supposed to happen at late Eocene and caused strong uplift and erosion of early syn-rift sequences. Quantitative analysis suggests that up to 10 km thick magmatic underplating below the thick crust requires a highly attenuated if not fully devastated mantle lithosphere below the continental slope during Eocene. Therefore, the breakup of South China Sea is supposed to experience an earlier mantle breakup and then a crust breakup to generate the spreading ocean. In comparison with Atlantic, the mantle below the northern continental margin might be wetter to generate such large amount of syn-rift magmatic underplating. Forward mathematical modeling suggests that a pre-rift subduction may provide the mechanism of both unsteady lithospheric and more saturated mantle. This might explain why marginal sea basin usually has much wider underplating and more magma supply than the same spreading rate passive continental margin and ocean.
How to cite: Sun, Z. and Peng, T.: The structure and breakup mechanism of the South China Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5129, https://doi.org/10.5194/egusphere-egu25-5129, 2025.
The rifting and continental breakup styles of Marginal Sea Basins is illustrated by well-constrained Western Pacific examples consisting of the South China Sea (SCS), the Coral Sea (CS) and the Woodlark Basin. In these examples, rifting directly followed an orogenic event which provided a strong thermal and structural inheritance as initial conditions to their formation. In the SCS and the CS especially, the rifting style is characterized by wide rifting forming a succession of sub-basins with thin continental crust, controlled by low-angle normal faults. The formation and development of extensional faults are enhanced by the reactivation of former thrust faults.
The final stages of rifting and continental breakup are contemporaneous with significant magmatic activity in the distalmost part of these margins with the emplacement of volcanoes, dykes and sills. Continent-Ocean transitions (COTs) are characterized by a sharp juxtaposition of the continental crust against igneous oceanic crust suggesting that a rapid shift from rifting to magmatic spreading occurred. High extension rates prevent conductive cooling allowing the focusing of volcanic activity into sharp COTs, quickly evolving to oceanic magmatic accretion.
The rifting style and mode of continental breakup during the formation of Marginal Sea Basins and their margins differs significantly from that of Atlantic-type margins. In the latter, these differences are influenced by transient high mantle temperatures, which lead to thick magmatic crust (i.e. magma-rich margins), or low-extension rates and mantle depletion, which result in subcontinental mantle exhumation (i.e. magma-poor margins). The evolution of Marginal Seas Basins is also controlled by the initial rheological conditions inherited from the previous orogenic event, where a combination of elevated geothermal gradients and rapid extension rates are driven by kinematic boundary conditions. These conditions are influenced by the presence of nearby subduction zones.
How to cite: Mohn, G., Ringenbach, J.-C., Tugend, J., Legeay, E., Kusznir, N., Vetel, W., and Sapin, F.: Rifting and Breakup during Marginal Sea Basin formation: Differences from Atlantic-type margins, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16548, https://doi.org/10.5194/egusphere-egu25-16548, 2025.
Syn-rift sequences, breakup unconformities and magnetic anomalies have been widely used to date rifting. However, it is generally accepted that rift systems are diachronous, both along dip and strike, and that the rifting processes are complex and difficult to date, in particular at magma-poor rifted margins. Therefore, new approaches need to be developed to date rifting. In our study we use the stratigraphic record of vertical movements to date a specific rift event and its propagation. In this work, we focus on two origins of uplift during rifting. First, the necking process, which corresponds to onset of localized deformation and significant differential crustal thinning over 4 to 14 my. Necking may result in a characteristic, fast and short-lived uplift limited to the future distal margin, followed by its fast subsidence (Chenin et al., 2018). Second, dynamic topography, which refers to a large wavelength (from 1,000 to 4,500 km) and fast (35 to 400 m.Ma-1) uplift (Jones et al., 2012), due to convection/heterogeneities within the asthenospheric mantle, not necessarily linked to rifting. In our study, we use the example of the widely studied Late Jurassic to Early Cretaceous southern North-Atlantic magma-poor rift system, forming the present-day West Iberian margin, its conjugate the Newfoundland margin, and the Bay of Biscay rifted margin. Thanks to the specific and characteristic fingerprints of each of the two types of vertical movements, they can be used to date rifting in an absolute and relative way. The necking signal dates a distinct event at a rift-segment scale, allowing to date the along strike diachronous evolution of the rift system. In contrast, the dynamic topography uplift occurs over a very wide area and is linked to simultaneous uplift and well-defined erosional unconformities that are time equivalent to a sudden increase in sedimentation rates offshore. Then, dynamic topography events occurring during rift propagation, could be considered as isochrons across a large area, allowing for along strike time correlations
Our preliminary results show a northward propagation of necking, which is consistent with the northward propagation of continental breakup already documented along the Iberian/Newfoundland conjugated margins. Secondly, we identify a dynamic topography event. Indeed, a Barremian to Aptian/Albian event can be defined by a large-scale uplift (e.g., Massif Central, Provence (France) and Southern England) that occurs at the same time of an increase in sedimentation rates and a change in seismic facies documented at the distal margins in the southern North Atlantic. The identification of these two types of events thanks to geological fingerprints and their relatively short duration, allows us to date rifting in the Iberian-Bay of Biscay system. While vertical movements associated with necking allow us to directly date the onset of crustal thinning and rift localisation, dynamic topography does not date a particular rift moment, but allows us to define an isochronous event that can be used for along strike time correlations and thus, for relative dating within propagating rift systems.
How to cite: Mathey, R., Autin, J., Manatschal, G., Sauter, D., Chenin, P., and Erratt, D.: How to date rifting thanks to vertical movements?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8638, https://doi.org/10.5194/egusphere-egu25-8638, 2025.
Rifted margins mark the transition between a thick-crusted (35 ± 5 km) continental domain and a thinner-crusted (0–8 km) (proto-)oceanic domain. Yet, the mechanisms of crustal thinning during rifting are incompletely understood, especially the consequences and fingerprints of the so-called necking phase during which the continental crust is thinned from its initial thickness to ca. 10 km in only a few million years.
One major difficulty in studying necking arises from the necking phase being only transient in the timeframe of continental rifting and often followed by further extension and thermal relaxation. As a result, the structural, stratigraphic and thermal signatures of the necking process are partially dismembered and overprinted in present-day rifted margins. Hence, studying the necking process requires to identify and track its fingerprints in present-day rifted margins.
In this contribution, we synthesize data from the best calibrated necking domains worldwide to define general recognition criteria and hence clarify the definition of necking. We show that necking domains commonly display: (1) deformed (from cataclasites to black gouges) basement directly overlain by undeformed syn-rift sediments; (2) exhumation of deep continental crust; (3) syn-rift basement erosion and adjacent sandstone deposition; and (4) syn-rift and syn-tectonic shallow-water deposits rapidly followed by syn-rift but post-tectonic deep-water deposits. We argue that these fingerprints cannot be explained by high-angle normal faults by themselves and discuss the possible additional and/or alternative processes.
How to cite: Chenin, P. and Manatschal, G.: Fingerprints of necking domains at rifted margins: insights from the best documented examples worldwide, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6434, https://doi.org/10.5194/egusphere-egu25-6434, 2025.
The rifted margins of the NE Atlantic are among the most extensively studied regions in the world thanks to the extensive geological and geophysical data available for this area. Despite this extensive research, uncertainties remain regarding the timing and mechanisms of rifting. Key questions include the volume of magma, recognized as underplated layer in the lower crust, the precise position of the Jan Mayen Microcontinent, and the extent of rifting that preceded the final opening of the NE Atlantic in the Paleogene. These uncertainties have significant implications for plate reconstruction models.
In this contribution, we combine interpreted seismic stratigraphy with plate rotations to define a new plate reconstruction model of the study area, spanning from mid-Permian to early Eocene. Stretching and pre-drift extension for individual rifting events are derived from a set of conjugate crustal transects evenly distributed along the NE conjugate margins, allowing to identify “restored” position of the continent-ocean boundaries (COB) back in time. Using an optimization approach, we derive Euler Poles that best-fit fixed and rotated restored COBs of the Eurasian and North American plates. Our approach incorporates uncertainties in COB location and the amount of magma added to the lower crust.
First results indicate a tighter pre-break-up fit between Greenland and Eurasia than previously suggested, implying that earlier models underestimated stretching. Implementing the obtained Euler Poles to plate reconstruction software GPlates highlights the four distinct rifting events. Our new plate reconstruction model offers improved insights into passive margins affected by multiple rifting events and can inform further studies on paleogeography, rift dynamics and break-up kinematics in the NE Atlantic region.
How to cite: Haas, P., Abdelmalak, M. M., Shephard, G. E., Faleide, J. I., and Berndt, C.: Plate tectonic modeling of multi-rifting events in the NE Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9069, https://doi.org/10.5194/egusphere-egu25-9069, 2025.
Salt tectonics at rifted margins involve intricate interactions between weak, ductile evaporite layers and brittle sedimentary rocks. Fully coupled geodynamic and surface process modeling can provide new insights into the dynamic controls on salt tectonics. We adopt such a modeling tool (ASPECT + FastScape) to investigate the evolution of salt-detached systems on magma-poor rifted margins.
Firstly, we investigate the controls on the temporal changes in the seaward translation velocity of salt and overlying sediments and the impacts of salt translation on the deformation of salt and overburden. Our modeling results indicate that translation velocities of salt and overburden first quickly increase to a peak value, controlled by highly nonlinear salt rheology, then slowly drop as the salt layer thins and welds. Thicker salt deposits generate higher peak translation velocities. Moreover, rapid salt translation creates wide, low-amplitude rollovers in the upslope extensional domain, irregularly spaced collapsed diapirs in the midslope domain, and complex diapir structures in the downslope contractional domain. Slow translation, on the other hand, produces regularly spaced salt pillows and diapirs in all domains. Asymmetric minibasins in translational and compressional domains interact with adjacent diapirs, forming strongly upturned and overturned strata.
Secondly, we investigate the dominant controls on salt-detached systems at different stages of rifting. We test three scenarios in which salt deposition occurs at early (scenario 1), middle (scenario 2), and late (scenario 3) stage of rifting, respectively. In scenario 1, salt is subject to continued extension, is offset by basement faults, and is separated into disconnected subbasins. In scenarios 2 and 3, the initial salt basin is more extensive than in scenario 1. A large-scale shear zone develops within the salt layer, assisting seaward translation of salt. Salt diapirs form preferentially on the slope and in deep water. We also find that submarine sediment transport efficiency strongly affects the final salt tectonic architecture. Our models show that less efficient marine sediment diffusion results in larger base-salt relief and hence promotes salt diapirism and minibasin formation.
How to cite: Ding, X., Wang, Z., Brune, S., Dooley, T., Moscardelli, L., Neuharth, D., Glerum, A., Rouby, D., Fernandez, N., and Hudec, M.: Geodynamic modelling of salt tectonics and translation speed at rifted continental margins, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10665, https://doi.org/10.5194/egusphere-egu25-10665, 2025.
The margins bounding the Equatorial Atlantic were formed during the Cretaceous due to the breakup of Gondwana. Rifting led to the development of sedimentary basins between West Africa and South America. We have used a grid of ~10,000 km of 2D seismic data to investigate the crustal structure along ~600 km of the NE Brazilian margin, containing the eastern Ceará and Potiguar Basins. The dataset is provided by the Brazilian National Agency of Petroleum (ANP).
We have interpreted fault structure and sediment units and mapped key horizons (top synrift, top basement, and Moho), across the entire seismic grid to produce surface and thickness maps of the main units. The basement thickness, synrift thickness, and Moho structure maps revealed that the margin tectonic structure is divided into three main tectonic domains: the Southern, Central, and Northern segments. The Southern Segment is characterized by abrupt lateral basement thinning and steep faults forming a main fault system indicating strike-slip kinematics. In contrast, main extension in the Central and Northern Segments is associated with normal faulting kinematics. These two segments represent different styles of faulting because the focalization of the extensional deformation is decoupled and occurred farther outboard along the Central Segment. The Northern Segment displays a comparatively thinner basement and thicker synrift deposits across much of the margin, compared to the Central Segment. These differences appear to imply that crustal extension occurred at different rates.
The three segments are separated by tectonic boundaries defined in seismic images by abrupt lateral changes in basement structure. The main segments may also contain sub-segments where changes in structure are more subdued. The imaged segment boundaries form a consistent linear structure visible from under the continental shelf to the deep-water basin. Their geometry indicates the evolution over time of continental segmentation during rifting. Furthermore, the orientation of these boundaries is similar for all segments supporting that they approximately correspond to flow lines indicating the opening direction during rifting. Most segment boundaries during rifting spatially correlate with fracture zones on the oceanic plate, indicating a relationship between continental tectonic segmentation and oceanic magmatic segmentation. We propose that the tectonic segmentation of the margin appeared during Barremian-Aptian time as a lithospheric-scale response of the mode of deformation caused by a change in plate kinematics that imposed a change in opening direction.
How to cite: Fonseca, J., Ranero, C., Vannucchi, P., Iacopini, D., and Vital, H.: Tectonic Segmentation During Rifting of the Brazil Equatorial Margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11099, https://doi.org/10.5194/egusphere-egu25-11099, 2025.
Passive continental margins and sedimentary basins are key domains for understanding long-term geological processes driven by complex Earth dynamics, such as continental rifting, magmatism, and sub-lithospheric interactions. These processes shape regions and leave distinct, spatially variable imprints in the sedimentary record. Deciphering these records helps us understand the dynamic relationships between geological processes on passive margins and quantify the interplay among tectonic, magmatic, and sedimentary forces that influence basin architecture.
In this study, we model the thermal-kinematic history of the southern Vøring Basin, offshoreMid-Norway, along a regional 2-D transect, integrating basin- and lithosphere-scale processes through time-forward basin modeling and an automated inverse basin reconstruction approach. The results indicate that the evolution of the inner Vøring Margin can be explained by standard lithosphere extension models. However, these models fail to account for key observations at the outer volcanic province, such as regional uplift at breakup, excess magmatism, and higher geothermal gradients. These discrepancies suggest additional processes are involved. Excess magmatism and uplift may be linked to sub-lithospheric mantle processes, such as the arrival of the Icelandic mantle plume or small-scale convection. Melt retention in the asthenosphere, along with mantle phase transitions during extension, could enhance uplift.
The best-fit model must explain the following key observations at both the inner and outer margins: (1) observed stratigraphy and subsidence, (2) beta factors along the transect, (3) vitrinite reflectance, particularly the high %Ro values at the outer margin, (4) base Eocene paleobathymetry, with an emergent outer margin and structural highs, and (5) the interpreted magmatic underplate beneath the outer margin.
We test various tectono-thermal models that include or exclude these processes. Models incorporating a plume emplaced at Eocene time, accounting for magmatic processes like melt retention and underplating, successfully reproduce the observations at the outer volcanic margin. This supports the contribution of the hot Icelandic plume to the Vøring Margin's evolution.
How to cite: Abdelmalak, M. M., Faleide, J. I., Midtkandal, I., Druga, A., Aldinucci, M., Zastrozhnov, D., Tsikalas, F., and Gac, S.: Basin modelling of the complex multi-rift system on Southern Vøring Margin : mechanisms and implications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13337, https://doi.org/10.5194/egusphere-egu25-13337, 2025.
The Northeast Atlantic is a key region where advances in plate tectonics have been developed, tested, and refined. Final breakup and the onset of seafloor spreading started around magnetic Chron C24n (~55 Ma; earliest Eocene). However, prior to breakup, the Northeast Atlantic’s margins underwent at least four discrete phases of lithospheric-scale rifting and basin formation, extending back to mid-Permian times (ca. 264 Ma) following the Caledonian orogeny. The total amounts of extension are in the order of several hundred kilometers and therefore relevant to implement in regional and global plate tectonic reconstructions. Recently, deformable plate models using the GPlates software have emerged as a tool to capture such non-rigid domains. However, deformable models to-date have been largely constructed in an overall rigid plate framework, applying pre-existing Euler rotations from the surrounding plates to the intervening rift. Here we detail why, and how, a basin-to-plate scale approach should be considered in future regional and global refinements of deforming reconstructions, using the multi-phase Northeast Atlantic rifting as a focus site.
We place basin-scale observations based on extensive seismic, stratigraphic and geophysical interpretations for the Norwegian margin and its Greenland conjugate (Abdelmalak et al. 2023) into new digital plate tectonic model (Shephard et al., in review). Central to our methodology is identification and restoration of rift basin hinges, and accounting for their along-margin variability. In this presentation we will detail the timing, location, amount and direction of extension across four discrete rift phases and their associated time-dependent rotations. A conjugate profile from the Foster and Northern Vøring margins (totalling 282 km of extension at average rates ranging between 0.13-0.58 cm/yr during rifting) yields the best fit accounting for along-margin heterogeneity whilst retaining the overall rigid framework requirements. We compare our results to previous regional models, including Barnett-Moore et al. (2018) and Müller et al (2019), and showcase some of the GPlates scalar field functionality including crustal stretching and tectonic subsidence. Finally, we have also developed an external routine for a backward-restored crustal thickness workflow which successively restores present-day thickness in conjunction with our deformable model.
How to cite: Shephard, G. E., Abdelmalak, M. M., Faleide, J. I., Clennett, E., Gac, S., Zahirovic, S., Haas, P., Gaina, C., and Torsvik, T. H.: A basin-to-plate deformable plate framework to capture the multi-phase rifting of the Northeast Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13989, https://doi.org/10.5194/egusphere-egu25-13989, 2025.
The Demerara Plateau is a submarine bathymetric high, 230 km-long and 170 km-wide, lying between 1000 and 3000 m-depth, and located north of French Guiana and Suriname shelves. On its northeastern border, the Bastille Plateau is a 16 km-long, 9 km-wide relief, at the intersection of the Cretaceous transform and divergent margins of the Demerara Plateau. It represents a crucial witness for understanding the early stages of the Equatorial Atlantic opening. Seismic profiles from GUYAPLACa (2003) and MARGATSb (2016) cruises reveal that the Bastille Plateau is a continentward tilted block with a planar top surface culminating at bathymetric depths of 3650 m, 15 km from the continent-ocean boundary. In 2016, the DRADEMc cruise dredged the rocks outcropping along the northern slope of the Bastille Plateau, retrieving mostly trachy-basalts and a single rudstone sample. During the DIADEMd campaign (2023), a dredge on the southern slope and two Nautile submarine dives confirmed that the Bastille Plateau was almost entirely made up of magmatic material. Three pelagic carbonates were sampled during one Nautile dive and came directly from the top of the Bastille Plateau, between 3745 m and 3685 m-depth.
We combine petrology with absolute U-Pb dating on calcite for the rudstone, and biostratigraphic dating of the pelagic carbonates deposited at the top of the Bastille Plateau to constrain the chronology of the rifting of the Equatorial Atlantic along the Demerara Plateau. We interpret the rudstone as deposited on a subaerial unconformity surface, similar in seismic lines to the post-rift unconformity. U-Pb analyses on calcite date this post-rift unconformity as Mid-Albian and constrain a continental break-up at 106 ± 9 Ma. Unexpectedly, post-rift subsidence did not follow the break-up, with marine transgression occurring circa 103 Ma on the Demerara Plateau, but later than 98 ± 3 Ma on the Bastille Plateau, closer to the continent-ocean boundary, possibly in relation with the vicinity of the Sierra Leone hotspot. Biostratigraphic ages indicate that subsidence was rapid from the Cenomanian onward, resulting in the early establishment of a deep-sea current acceleration zone along the outer margin of the Demerara Plateau.
a https://doi.org/10.17600/3010050
b https://doi.org/10.17600/16001400
c https://doi.org/10.17600/16001900
d https://doi.org/10.17600/18000672
How to cite: Coudun, C., Bienveignant, D., Basile, C., Girault, I., Giraud, F., Vezinet, A., Loncke, L., Graindorge, D., Klingelhoefer, F., Léger, J., Menini, A., and Heuret, A.: Unexpected post-breakup altitude of the distal continental margin of the Demerara Plateau (French Guiana): New constraints from LA-ICP-MS U-Pb calcite dating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18237, https://doi.org/10.5194/egusphere-egu25-18237, 2025.
The factors controlling the structure and morphology of oblique rifted margins remain enigmatic. Key features requiring explanation include: (1) long transform fault systems (>300 km) with transpression or transtension, (2) rift segments with varying asymmetry and obliquity, and (3) complex, variable drainage systems along the rift. We use large-scale 3D coupled thermo-mechanical and surface process models to explore how inherited transform weakness zones influence the structure and morphology of oblique rifted passive margins. Our results show that the orientation of inherited weaknesses determines the degree of transpression or transtension along transform faults, while the extent of over- or underlap among weaknesses controls segment obliquity and asymmetry, shaping fluvial drainage networks. These findings provide a conceptual framework to interpret the key structural and morphological characteristics of oblique rifted margins in the Equatorial Atlantic, North Atlantic/Arctic, and Mozambique regions.
How to cite: Theunissen, T., Huismans, R. S., Rouby, D., Wolf, S. G., and May, D. A.: Inherited transform weaknesses control structure and morphology of highly oblique rift-transform systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6786, https://doi.org/10.5194/egusphere-egu25-6786, 2025.
The Chukchi Basin, a sub-basin of the Amerasia Basin in the Arctic Ocean, remains enigmatic regarding its formation age and tectonic processes. Among the various hypotheses proposed, seafloor spreading or hyper-extended rifting during the Cretaceous are currently prominent, both supported by gravity and deep seismic survey data. Recent marine heat flow (MHF) observation efforts using the IBRV Araon from 2018 to 2024 have resulted in a comprehensive dataset covering the basin along and across the inferred N-S oriented spreading axis in the basin center. The formation age inferred from the newly observed MHF was the Early to Late Cretaceous, which is slightly older than the timing of Northwind Basin to the east. Notably, the MHF distribution revealed an asymmetric increase toward the eastern margin perpendicular to the axis and toward to southern margin parallel to the axis. Because MHF distribution often reflects deep tectonic structure such as the Moho depth or the lithosphere-asthenosphere-boundary, this asymmetric pattern suggests a difference in the depth of these boundaries within the basin. The observed discrepancy between the inferred spreading axis and the MHF distribution indicates that the Chukchi Basin may have undergone asymmetric rifting, challenging the conventional notion of symmetric rifting. Our future research will integrate gravity and magnetic anomaly data with numerical modeling to better constrain the deep structure and formation processes of the basin.
How to cite: Kim, Y.-G., Hong, J. K., Jin, Y. K., and So, B. D.: Asymmetric distribution of marine heat flow in the Chukchi Basin (Chukchi Abyssal Plain) as possible evidence for asymmetric rifting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3906, https://doi.org/10.5194/egusphere-egu25-3906, 2025.
While it is well documented that continental extension involves discrete tectonic or magmatic rifting events, little is known about how deformation accumulates between these events. Here we focus on strain localization across the Natron Basin, which is part of the eastern branch of the East African Rift, that experienced a major tectono-magmatic event in 2007.
A cross-rift profile of horizontal GNSS velocities (2013–2017) reveals a gradual transition between the rigid Tanzanian Craton and the Somalian Plate, with ~2 mm/yr of extension distributed across ~100 km (stretching zone). Such a pattern is commonly interpreted through the lens of dislocations in an elastic half-space. Here, an east-dipping border fault locked down to ~10 km may explain the observed width of the stretching zone, provided it extends to great depths, and creeps at a constant rate of ~3 mm/yr. The extent to which this is compatible with a hot lower crust riddled with magmatic intrusions is still debatable.
We thus explore an alternative model where the width of the stretching zone is entirely determined by the history of past, finite deformation, and the corresponding ambient stress state. We use a 2-D thermo-mechanical model to stretch a visco-elasto-viscoplastic brittle layer, first creating a major border fault that slips continuously, flexing its footwall and hanging wall. We then artificially “lock” this fault by instantaneously strengthening it, drastically reduce our computational time steps, and continue stretching the layer. While the system should behave as an homogeneous, elastic layer under far-field extension, i.e., produce a linear displacement profile, we obtain an arctangent-shaped profile with a characteristic stretching zone width.
This suggests that strain localization is controlled by the heterogeneous distribution of pre-existing stresses. Specifically, regions of high stresses that accrued during flexure of the fault blocks are brought to failure first during inter-event stretching, prompting the localization of elasto-plastic strain in a wide zone centered on the border fault. This process explains the width of velocity gradients in rift zones without invoking a deep, continuously creeping fault.
We therefore suggest that long-term stress buildup plays a key role in short-term strain localization, and discuss its implications for active deformation in magma-rich continental rift settings like the Natron Basin.
How to cite: Navarrete, I., Olive, J.-A., Calais, E., Dalaison, M., and de Monserrat, A.: Inter-event strain localization modulated by background stresses across the Natron Basin, East African Rift, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5777, https://doi.org/10.5194/egusphere-egu25-5777, 2025.
Magma-rich continental rifts comprise en-echelon magmatic segments where magmatism and extension are localised, similar to slow and ultra-slow spreading centres. While rift segmentation is clear in mid-ocean ridges, it is less so in continental rifts like the Main Ethiopian Rift (MER). Faulting within the MER initiated at ~11Ma at the border faults which define the overall NE trend of the MER and are oblique (30°-45°) to the E-W extension direction. However, since ~2Ma extension has localised to the right-stepping Wonji Fault Belt (magmatic segments), in which small offset faults and alignments of volcanic features strike roughly orthogonal to the extension direction. Despite this general framework, there is a lack of quantitative analysis to understand rift segmentation and its relationship to volcanic systems, and how segments interact. It is unclear how the ratio of magmatic to tectonic processes varies along rift segments.
Using optical satellite imagery and SRTM digital elevation data with a resolution of 1 arc-second, we map fault traces, calderas, and volcanic craters in the central and northern MER at a scale of 1:100,000. We also map scoria cones in the same region using optical imagery at 1:20,000. This data is integrated with existing MER datasets, including previously mapped fault traces, digital elevation models, mafic intrusions derived from gravity data, InSAR-derived locations of magma bodies, and recent dyke intrusions between Fentale and Dofan to define the magmatic segments. We investigate characteristics and scales of MER magmatic segments by analysing fault trace patterns, along-segment displacement variations, elevation profiles, the distribution of volcanic activity, and shallow crustal density structures.
How to cite: Farrell, C., Keir, D., Corti, G., Sani, F., and Maestrelli, D.: New insights on segmentation of fault and magmatic systems in the Main Ethiopian Rift, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3745, https://doi.org/10.5194/egusphere-egu25-3745, 2025.
Within Central Europe, remnants of the Variscan orogeny are found today at elevations exceeding 1000 m. Among these remnants are the Black Forest and Vosges Mountains that are separated by the N-NE-oriented Upper Rhine Graben. Subsidence of the Upper Rhine Graben began during the Eocene and was accompanied by the uplift of Variscan basement, which is now exposed in the Vosges Mountains and Black Forest at the western and eastern rift flanks, respectively. Overlying Mesozoic sediments have been extensively eroded, exposing the Variscan bedrock and confining the younger sediments to isolated, higher-elevation areas. The unloading of the lithosphere due to the erosion of 2 km of sediments amplifies the uplift due to flexural isostatic adjustment.
The Black Forest has been the focus of several low-temperature thermochronology studies, including zircon and apatite fission track analyses as well as apatite (U-Th)/He dating. In contrast, the Vosges Mountains have received significantly less attention, with no published apatite (U-Th)/He ages available. Results from previous fission track studies suggest a complex thermal history for the region, including a transient heating episode during the initial rifting phase, as well as recent hydrothermal events that have influenced the thermochronological measurements. However, the total amount of exhumation and the timing and extent of rock uplift remain so far unconstrained.
In this study, we aim to further constrain the thermal evolution of the region using more than 30 new apatite (U-Th)/He ages from two E-W profiles across the Upper Rhine Graben and its rift flanks. Samples were collected from outcrops previously dated using apatite fission tracks or, where unavailable, along new horizontal and vertical profiles. The southern profile spans the highest peaks, connecting the eastern edge of the Black Forest with the western edge of the Vosges Mountains. The second profile is located along the northern borders of the two mountain ranges.
How to cite: Dremel, F. C., Villamizar-Escalante, N., Heberer, B., Schönleber, L., Friedrichs, B., Robl, J., and von Hagke, C.: Constraining Exhumation and Rift Evolution in the Vosges and Black Forest Using Apatite (U-Th)/He Thermochronology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15767, https://doi.org/10.5194/egusphere-egu25-15767, 2025.
The Saih Hatat Dome (SHD) in NE Oman forms a tectonic window revealing in an area of approximately 95 km by 50 km the par-autochthonous Neoproterozoic basement of the Arabian Plate and its Cambrian to Early Cretaceous cover. The SHD is surrounded by the allochthonous Samail Ophiolite and underlying nappes consisting of mostly sedimentary rocks from the Neo-Tethyan Hawasina Basin.
Within this dome, the Hulw Window exposes rocks that were subducted to depths of >30 km during the Late Cretaceous (Agard et al. 2010) and were subsequently exhumed and tectonically emplaced beneath low-grade metamorphic rocks, forming what is referred to as the "Lower Plate". The Hulw Window consists of marbles, metadolostones, and calcareous micaschists, with embedded mafic and felsic metavolcanic rocks. The entire Hulw unit underwent Late Cretaceous high-pressure/low-temperature metamorphism.
Earlier studies assumed Pre-Permian ages for the protolith for the metamorphic rocks of the Hulw unit (e.g. Miller at al. 2002). Newly obtained U-Pb zircon LA-ICP-MS data from felsic metavolcanic rocks yield ages of 283 ±2.9 Ma and 269 ±3.7 Ma, indicating an Early to Middle Permian volcanism.
Two blueschist-facies quartzites from the southern Hulw unit contain concordant detrital zircons, ranging in age between c. 530 and 2872 Ma with age clusters around 750 to 850 Ma and 1010 to 1164 Ma. The latter ages are not known from an Arabian source and might be derived from an Indian source. The maximum depositional age of the sediments is therefore Early Cambrian.
Field studies in the central part of the SHD revealed numerous mafic dykes, some reaching widths of up to 4 m. These dykes are oriented WNW-ESE and NE-SW. Zircons from one dolerite dyke yields an age of 267 ± 3.7 Ma, indicating that the mafic and felsic magmatism occurred simultaneously.
Whole-rock geochemical data of the mafic volcanic rocks demonstrate a significant partial melting trend, suggesting an increasing degree of upper mantle melting. The felsic metavolcanic rocks are classified as subalkaline to mildly alkaline rhyodacites, which are derived from crustal melting typical of early rift stages.
Overall, the SHD displays a progressive increase in Permian subvolcanic and volcanic rocks from the southeast toward the northwest, characteristic of rift-related crustal extension. This extension ultimately led to the opening of the Neotethys and the separation of the African/Arabian Plate from the Central Iranian/Qiantang blocks and the Indian Plate at a triple junction (Torsvik et al. 2014).
References
Agard, P., Searle, M.P., Alsop, G.I., Dubacq, B., 2010. Crustal stacking and expulsion tectonics during continental subduction: P-T deformation constraints from Oman. J. Struct. Geol. 26, 451-473.
Miller, J.M., Gray, D.R., Gregory, R.T., 2002. Geometry and significance of internal windows and regional isoclinal folds in northeast Saih Hatat, Sultanate of Oman. J. Struct. Geol. 24, 359-386.
Torsvik, T.H., van der Voo, R., Doubrovine, P.V., Burke, K., Steinberger, B., Ashwal, L.D., Trønnes, R.G., Webb, S.J., Bull, A.L. 2014. Deep mantle structure as a reference frame for movements in and on the Earth. Proc. Natl. Acad. Sci. USA 111, 8735–8740.
How to cite: Bauer, W., Qasim, M., Jacobs, J., Callegari, I., and Scharf, A.: Timing of Permian rifting in the Saih Hatat Dome (Sultanate of Oman), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-22, https://doi.org/10.5194/egusphere-egu25-22, 2025.
The Middle Proterozoic period (1800–800 Ma), often called the "Boring Billion", was characterized by a stable environment with low atmospheric oxygen levels and globally anoxic oceans. In East Asia, this period has been frequently linked to the breakup of the Columbia supercontinent at ca. 1400 Ma, as evidenced by widespread litho-stratigraphic evidence (e.g., Bayan Obo, Yanliao, Xionger rift systems) of rifting in the North China Craton. Similar Mesoproterozoic rift-related lithologies have been identified in the Hwanghae Rift Zone (HRZ) on the northern Korean Peninsula (Jon et al., 2011; Han et al., 2013), suggesting that the Korean Peninsula may have been a part of the global-scale rift system associated with the disruption of the Columbia Supercontinent.
From this point of view, this study examines the tectonic evolution of banded-iron formation (BIF)-bearing metamorphosed sedimentary and volcanic successions in the Western Gyeonggi Massif of the Korean Peninsula. The meta-sedimentary sequences consist of quartzite, biotite-muscovite schist, BIF, and marble, while the volcanic suite comprises amphibolite and meta-gabbro, occurring as clasts, boudins, and blocks within the marble beds. All the rock types exhibit amphibolite facies metamorphic alterations and deformations. Intercalation of quartzite with Algoma-type BIF suggests siliciclastic sedimentation concurrent hydrothermal Fe input from deep-seated faults in a matured continental shelf environment. The carbonate deposition indicates biological activities on the volcanic atoll in the calm marine environment, following active volcanism. The dismembered amphibolite blocks or lenses show massive, igneous textures, and sub-alkaline basaltic composition, with trace and rare earth element patterns resembling ocean island basalt (OIB) and enriched mid-ocean ridge basalt (E-MORB), indicative of rifting of continental landmass similar to modern-day Iceland driven by plume-ridge interactions. U-Pb zircon dating of dismembered amphibolite blocks or lenses reveals ca. 1419 Ma protolith age followed by ca. 251 Ma metamorphism. These findings represent the earliest Mesoproterozoic volcanism and sedimentation recorded in the central-western margin of the Korean Peninsula, which has been considered part of the Permo-Triassic collisional belt. We propose that the central-western margin of the Korean Peninsula witnessed rifting concurrently with its northwestern margin, coinciding with rifting in the North China Craton (e.g., Bayan Obo, Yanliao, Xionger rift systems) as part of the global rift system associated with the disruption of Columbia supercontinent during the "Boring Billion".
How to cite: Jang, Y., Samuel, V. O., Kwon, S., and Santosh, M. W.: Tectonic evolution of the proto-Korean Peninsula in the Boring Billion: Implication for the disruption of the Columbia Supercontinent, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5492, https://doi.org/10.5194/egusphere-egu25-5492, 2025.
Low-angle normal faults (LANFs), characterized by dips of less than 30°, are frequently observed in rifted margins. Despite extensive research, the mechanical processes governing LANFs remain poorly constrained, raising critical questions about the angle at which they initiate, their evolution during extension, their three-dimensional geometry, and related deformation in the hanging-wall and footwall. Addressing these issues is essential for understanding extensional processes in such tectonic settings, including thinning of the continental crust and the exhumation of mantle material in rifted margins.
The Err and Bernina extensional detachment systems, within the lower Austroalpine nappes of the Central Alps, offer a rare natural laboratory for studying LANFs. Formed during the Jurassic rifting in the distal Adriatic rifted margin preceding the formation of the Alpine Tethys, these LANFs are exceptionally well-preserved despite the subsequent deformations from the Alpine orogeny.
This study presents results from extensive field campaigns conducted between 2022 and 2024, during which high-resolution data were collected over a ~100 km² area using Unmanned Aerial Vehicle (UAV) surveys supplemented by field mapping. Rigorous quality control and processing ensured the generation of 3D high-resolution digital outcrop models (DOMs) of the Err and Bernina extensional detachment systems, implementing differential positioning and SwissTopo terrain data for a resulting spatial error of less than 1 meter. The DOMs provide centimetre to decimetre-scale details that facilitate mapping of the spatial evolution of LANFs and the tectono-sedimentary architecture of the overlying allochthonous blocks. Detailed interpretations reveal their internal structure, including lithological changes, deformation patterns, and fault structures at various scales. Additionally, we characterized the sedimentary basins formed during the Jurassic extension, shedding light on their development and spatial relationships with the detachment systems. Comparison of our findings with seismic data across present-day low-angle normal fault systems bridges the scale-gap between detailed field-based analyses and large-scale seismic interpretations, providing crucial new insights to the evolution of LANFs.
How to cite: Morzelle, L., Mohn, G., Betlem, P., and Tugend, J.: High-resolution digital outcrop models of low-angle normal faulting: the fossil distal Adriatic rifted margin (SE Switzerland), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6051, https://doi.org/10.5194/egusphere-egu25-6051, 2025.
The Dniepr-Donets Basin (DDB) represents a significant intracontinental rift system in Europe, whose formation remains an ongoing topic of research. Central to this investigation is whether the basin developed through passive rifting—driven by far-field tectonic stresses such as back-arc extension—or active rifting, which involves localized thermal anomalies from processes like mantle plume activity. This research seeks to address these competing models through integrated geological and geophysical analyses, contributing to our understanding of continental rift evolution.
This project involves interpretation of 23 regional seismic reflection and refraction profiles including “classical” seismic profiles: DOBRE’99 and Georift-2013. The seismic data will be calibrated by c. 4000 wells with stratigraphy. Seismic analysis will be focused on mapping of 14 key stratigraphic horizons covering the entire area of the DDB (~76,900 km2). The spatial orientation of structural elements will be resolved using potential field anomaly maps. Integration of the interpreted surfaces with the borehole stratigraphy will allow for determining the age of major unconformities and faulting. The evolution of the DDB will be quantitatively analysed using cross-section balancing technique along selected regional seismic profiles.
A key aspect of this work involves constructing a three-dimensional structural model of the DDB using borehole and seismic data. This model, still under development, aims to provide detailed insights into the basin’s geometry, sedimentary layer distribution, and fault system configuration. Particular emphasis is placed on identifying structural asymmetries, which could suggest the operation of simple-shear mechanisms often linked to passive rifting. By correlating surface geological features with deep crustal structures, this research is gradually building a comprehensive picture of the basin’s evolution.
Potential field data are also being analyzed to investigate mantle processes and their influence on rifting. Variations in gravity and magnetic fields are being studied for evidence of deep-seated magmatic intrusions and high-density bodies. This approach aims to evaluate whether mantle plume activity or crustal thinning contributed to the rifting mechanism, helping to distinguish between active and passive processes.
This ongoing research integrates data across crustal and mantle processes, with the goal of correlating mantle dynamics, surface volcanism, sedimentation patterns, and tectonic evolution. The findings aim to advance our understanding of intracontinental rifting and provide insights into the conditions under which rifting transitions to full continental break-up or remains an intracontinental feature, as in the case of the DDB.
How to cite: Nasiri, A., Stovba, S., Drachev, S., Stephenson, R., and Mazur, S.: Tectonic Evolution of the Pripyat-Dniepr-Donets-Donbas Basin: Insights into Intracontinental Rifting Mechanisms and Structural Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6348, https://doi.org/10.5194/egusphere-egu25-6348, 2025.
The Hellenides in Continental Greece is a tertiary alpine belt with complex tectonic units distributed into two major crustal domains: the External Zones and the Internal Zones, whose geological histories diverged mainly during the late Jurassic, when the internal zones got loaded by the emplacement of large ophiolitic nappes. The Frontal Thrust of the Internal Zones, later partly reactivated as the Main Pelagonian Detachment, marks the boundary between these two major tectonic domains. Since the Miocene, the entire Greek territory has been affected by back-arc extension associated with the southward slab roll-back of the Ionian subduction (Africa Plate). This extension has led to the exhumation of core-complexes and by the formation of numerous extensional basins in the Aegean Sea and two major rifts on mainland Greece: the Corinth Rift from about 4 Ma, and the Sperchios – North Evia Gulf Rift considered to open since 3.5 Ma. The first one is located within the External Zones, while the later developed mainly within the Internal Zones. The Corinth Rift has been extensively studied through various techniques and datasets, whereas the Sperchios – Northern Evia Gulf Rift has been less well-investigated.
We present new crustal cross-sections through the Sperchios – North Evia Gulf Rift interpreted from the analysis of recently acquired seismic data and from filed-based tectonic analysis. These sections reveal (1) the location and variability of major normal faults, and associated depocenters, and (2) the presence of a magmatic chamber in the eastern part of the rift. On the basis of existing data and on new data from receiver functions, we propose an improved version of the Moho depth map in this area. This updated map shows significant latitudinal asymmetries within the rifts, along with longitudinal asymmetries across the entire region. We propose two new Moho depth cross-sections to account for these depth variations and asymmetries: one through the western parts of the rifts and another through the eastern portions. In the west, our results show crustal thickening beneath the western domains of both rifts and crustal thinning beneath some particular zones of the Hellenides, particularly beneath the highly elevated Parnassus zone. To the east, the crustal configuration differs, with a shallower Moho beneath the rifts and a slight crustal thickening between them, under the Kifissos Basin. Furthermore, within the Sperchios – North Evia Gulf Rift, depocenters and major faults are not localized along the same rift boundary. To the west, deformation is largely controlled by faults forming the southern boundary of the rift, whereas in the east, major faults and associated depocenters are located along the northern boundary. We propose that the crustal thickening and thinning observed are related to the presence of deep detachments beneath the Corinth Rift and the western part of the Sperchios – North Evia Gulf Rift, including the Main Pelagonian Detachment that seems particularly important to constrain the present crustal geometries.
How to cite: Chanier, F., Caroir, F., and Tiberi, C.: Crustal asymmetries within the Corinth and North Evia Gulf rifts (Greece): Moho depth variations and structural inheritances, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18056, https://doi.org/10.5194/egusphere-egu25-18056, 2025.
Rift systems play a crucial role in the Wilson cycle, where the extension and breakup of continental plates can lead to the formation of new oceans. Earth's rift systems exhibit various stages, from initiation to breakup, with the latter representing 'successful' rifting, as observed along the Atlantic margins. Whereas rifted margins can record successful extensional plate dynamics, deformation can also stop at earlier stages or shift to more favourable locations, resulting in 'failed' rifts, such as the North Sea or the Atlas rift. However, the mechanisms that control whether a rift fails or is successful are not very well known.
Understanding the dynamics of continental extension and tectonic processes in rift systems requires examining their initial conditions and subsequent evolution, with the latter influenced by both strengthening and weakening processes of the lithosphere. Here we numerically simulate rift evolution using geodynamic finite-element 2D ASPECT models incorporating shear zone (“fault”) dynamics and strain softening within a visco-plastic rheological framework. We use the landscape evolution model FastScape to simulate surface processes.
To understand which processes lead to the success or failure of a rift, we explore the role of strengthening and weakening processes. Our modelled strengthening processes comprise (1) lithospheric cooling, which enhances the strength of ductile domains via temperature-dependent viscosity, (2) gravitational potential energy gradients that impose a degree of compression outboard of high-elevation domains; and (3) fault healing, which strengthens frictionally weakened regions over time as a function of temperature. We also account for the following weakening processes: (1) frictional softening, which causes an increase in fault activity; (2) lithospheric necking, which thins and thereby heats the lithosphere beneath the rift centre; (3) erosion and sedimentation, as simulated by FastScape, which alters the distributions of surface loads in a way that increases fault longevity. Within the framework of these processes, we examine the effects of crustal thickness, extension rate, rheology, and friction angle, on the spatial and temporal occurrence of rift success and failure. To quantify the results, we analyse fault geometry and dynamics, as well as the forces required for continued extensional plate motion.
Preliminary results indicate the existence of a lower limit for the full extension velocity to achieve breakup. For models with typical continental lithosphere this limit is ~2 mm/yr. Lithosphere that is extending at a smaller velocity thins temporarily but strengthening mechanisms ultimately outweigh weakening processes resulting in relocalisation of deformation. Our analysis highlights the internal and external processes that influence rift systems at different evolutionary stages and provides criteria for understanding and predicting rift evolution.
How to cite: Neumann, T., Brune, S., Buiter, S., Neuharth, D., and Jackson, C.: Modelling of lithospheric weakening and strengthening processes and their impact on rift success and failure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10113, https://doi.org/10.5194/egusphere-egu25-10113, 2025.
Normal faulting in continental rifts creates pronounced relief which evolves over time. At the same time, many rifts are marked by 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. It is clear that magmatic intrusions and normal faulting interact in magmatic rifts such as the Kenya Rift, the Main Ethiopian Rift, the Afar triple junction, and in the Icelandic plate boundary. However, 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 remains difficult to isolate from observations.
Previous modeling studies of time-dependent magma-tectonic interactions in extensional tectonic settings fell into one of two categories: (1) simple models where diking is represented by a prescribed fixed rectangular zone of horizontal divergence (e.g., Buck et al., 2005), (2) complex setups where magma ascent is represented by porous flow and fluid-driven fracture (e.g., Li et al. 2023). While the former approach can be applied to model of tens of millions of years of dike injection along spreading ridges, the simplicity prevents applications to continental rifts where magmatism manifests over broad areas. The latter approach allows to study the evolution of individual dikes, but its computational costs prevent application to lithospheric-scale rifts over geological times scales.
Here, we propose a numerical workflow that can be categorized as a model of intermediate complexity. We nucleate the dikes at the brittle/ductile transition above magma-forming regions. The dikes 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 have approached this problem and how we implemented it in the open-source community geodynamics model ASPECT. We show how the generated dikes are being focused in specific regions, and how the 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., and Atnafu Muluneh, A.: Modeling dike-fault interactions in continental rifts on geological time scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8867, https://doi.org/10.5194/egusphere-egu25-8867, 2025.
Lithospheric thinning initiates continental rifting and eventual break-up, driven by the interplay of tectonic, magmatic and surface processes. Recent findings from IODP expeditions and seismic surveys reveal that the northern South China Sea (SCS) margin exhibits distinctive features not typically alinged with classic magma-poor or magma-rich margins, including widespread detachment, syn-rift magmatism and a notably rapid transition from continental margin to seafloor spreading. However, the role of magmatism in the formation of detachments, which is key for elucidating the evolution of rifted margins, remains poorly understood. Here we use 2D numerical models to simulate the thermo-mechanical evolution of continental rifting, incorporating melt generation, emplacement and associated heat release. Our models reproduce the main observations from the northern SCS margin, including the hyper-extended crust, crustal boudinage, lower crust exhumation and dome structure. Particularly, we demonstrate that the thermal weakening related to the magmatism promotes the ductile lower crustal flow, which converges beneath a ‘rolling-hinge’ type detachment, facilitating the formation of core complex. Unlike magma-poor margins, the initial elevated lithospheric temperature by prior plate subduction and syn-rift magmatism from decompressing melting shape the ‘intermediate’ nature of the SCS margin. This work could provide valuable insights into how tectonic deformation and magmatism interact in continental rift systems around the globe.
How to cite: Yang, P., Pérez-Gussinyé, M., Liu, S., García-Pintado, J., and RaghuRam, G.: Magmatic controls on detachment fault formation at South China Sea rifted margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9481, https://doi.org/10.5194/egusphere-egu25-9481, 2025.
Total continental lithosphere extension prior to breakup and sea-floor spreading in the South China Sea (SCS), a marginal ocean basin, ranges from approximately 360 km in the NE to 580 km in the SW. In contrast, total continental lithosphere extension prior to breakup for the Iberia-Newfoundland rifted margins is no more than 180km. SCS extension leading to continental breakup is between x2 and x3 greater than for the Atlantic margin type.
In the case of Atlantic type margins, lithosphere deformation transitions from initially wide rifting to more localised stretching and thinning, a process termed necking. The necking domain at rifted continental margins, so produced, typically has crustal thickness of 25 km proximally decreasing to 10 km distally. Further lithosphere stretching and thinning due to hyper-extension and the onset of decompression melting results in the rupture and separation of continental lithosphere, the creation of a divergent plate boundary, and the initiation of sea-floor spreading.
The SCS shows very wide domains of thinned continental crust with thicknesses between 25 and 10 km; widths of thinned crust much greater than those of Atlantic type margins. These wide regions of thinned crust on the SCS margin take the form of crustal boudinage with multiple sag basins underlain by highly thinned crust separated by basement highs underlain by less thinned crust.
The localisation of lithosphere deformation before breakup, during the formation of Atlantic type margins, is due to failure of the initially strong cold lithospheric mantle lid. The same mechanism of localisation cannot occur to generate necking in the SCS; the SCS was formed by rifting of volcanic arc lithosphere in which the lithospheric mantle was already hot.
We attribute the very wide regions of continental crust with thicknesses between 25 and 10 km in the SCS, very much wider than for Atlantic type margins, to a weak inherited lithosphere rheology which favours extensional boudinage of the continental crust rather than crustal rupture and separation, and distributed rather than focused decompression melting of wet mantle from the inherited volcanic arc setting.
How to cite: Zhang, C., Kusznir, N., Manatschal, G., Chenin, P., Taylor, B., Sun, Z., Li, S., Suo, Y., and Zhao, Z.: Lithosphere Extension Prior to Continental Breakup in the South China Sea: Comparison with the Atlantic Type Rifted Margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7891, https://doi.org/10.5194/egusphere-egu25-7891, 2025.
The sedimentary basins of the Brazilian Equatorial Margin (BEM) are considered a key frontier for petroleum exploration. The BEM is characterized by transform tectonics, featuring oblique and divergent brittle structures occurring on the Foz do Amazonas, Pará-Maranhão, Barreirinhas, Ceará, and Potiguar basins. This tectonic pattern is also recognized in the West African marginal basins (Ghana, Ivory Coast, and Liberia), including those of Cote d’Ivoire and Ghana. The central sector of the BEM, where the divergent segments of the Pará-Maranhão Basin meet the transform segment of the Barreirinhas Basin. To better understand the tectonic framework, a comprehensive dataset, including seismic data, in addition to well data (gamma-ray, density, sonic profiles, checkshots, and biostratigraphy), was analyzed across 80,000 km². These data, reinterpreted considering modern understanding of the BEM evolution, provided insights into the structural and stratigraphic characteristics of the margin. The basins were classified based on the obliquity of their segments relative to the rift extension direction. This obliquity, defined by the angle between the transform faults and segment direction, was used to delineate four distinct crustal domains: the continental thinning domain, the hyper-extended continental domain, the mantle exhumation domain, and the oceanic domain. Each domain reflects different geological processes contributing to crustal evolution. The Pará-Maranhão divergent segment, which connects with the Barreirinhas transform segment, is oriented NW-SE with a 53° obliquity. This segment has a wider continental thinning domain due to its higher obliquity. The sequence of crustal thinning progresses from continental to oceanic, marked by normal faults, horsts, and grabens, indicating tectonic extension. The sedimentation in this region is mainly controlled by thermal and tectonic subsidence, with distinct rift (syn-rift), post-rift, and continental shelf sequences. Fault blocks rotate, creating listric faults and rollover systems that affect sedimentation. In contrast, the West Barreirinhas segment, which is aligned with the Romanche Fracture Zone, has a 0° obliquity. This transform margin features a narrow continental crust neck, with differential subsidence and steep post-rift slopes. Listric faults and large negative flower structures are characteristic of this segment. Overall, the variation in obliquity across the margin segments significantly influences the width of the crustal thinning domain, with higher obliquities resulting in wider thinning zones. The presence of thinned continental crust and exhumed mantle in the deep-water region, prior to the first occurrence of oceanic crust, is similar to the analysis of the African conjugate margin, which is associated with a hydrocarbon system based on Upper Cretaceous turbiditic sandstone reservoirs. The same potential reservoirs are also found in the Brazilian counterpart.
How to cite: Costa de Melo, A. C., de Castro, D. L., and Oliveira, D. C.: Tectonic Architecture of the Equatorial Atlantic Margin: Insights from the Central Segment of Brazilian Counterpart, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12592, https://doi.org/10.5194/egusphere-egu25-12592, 2025.
Volcanic rifted margins commonly form in association with the emplacement of Large Igneous Provinces. The intense associated volcanic activity coincides with shifts in the global carbon cycle and rapid climate change during several key geological periods and crises. The Mid-Norwegian and NE-Greenland conjugate rifted margins formed after late Paleocene to early Eocene continental breakup in association with the emplacement of the North Atlantic Igneous Province (NAIP). The NAIP and early opening of the North Atlantic occurred contemporaneous to a rapid 5-6 °C global warming episode known as the Paleocene Eocene Thermal Maximum (PETM). The rapid global warming documented during the PETM is hypothesized to result from the release of thermogenic gases into the atmosphere through thousands of hydrothermal vents. The gases were generated by contact metamorphism of carbon-rich sediments during the extensive sill emplacement from the NAIP. The potential climatic impact of these hydrothermally released greenhouse gases is dependent on the water depth at which they were released. Unless it is released in a shallow marine environment most methane, known for its significantly greater global warming potential compared to carbon dioxide, will be oxidized and dissolved in the ocean before it reaches the atmosphere.
First results of IODP Expedition 396 conducted on the Mid-Norwegian volcanic margin have documented the shallow marine to potentially sub-aerial setting of at least one of the hydrothermal vents (i.e. Modgunn vent). However, a comprehensive regional assessment of the water depth at which hydrothermal venting occurred remains necessary to validate the overall impact on paleoclimate and the PETM. To do so, we apply 3D flexural-backstripping and decompaction to remove the loading effects of sedimentary sequences and determine the sediment-corrected bathymetry down to the top Palaeocene surface at which most of the vents are mapped. Reverse subsidence cannot be directly modelled without knowing the detailed distribution of syn- and post-rift thermal subsidence from Cretaceous and Paleocene rifting as well as any mantle plume dynamic uplift during NAIP emplacement. Because these tectonic and geodynamic components of subsidence cannot be deterministically predicted at the required accuracy, we use local palaeobathymetric constraints from seismic observations and drilled biostratigraphic data, combined with our flexural backstripping and decompaction results to calibrate palaeobathymetric variations of the Paleocene venting surface at the time of the PETM.
Our results predict that hydrothermal venting occurred within a range of palaeo-water depths showing the complex palaeo-structure of the top Paleocene surface. Key post-Paleocene tectonic influences such as a well-documented Miocene doming episode influence the margin history, and hence, at this location, our palaeobathymetric results represent shallowest estimates and must be interpreted with caution. However, most of the vents (>80%) restore to bathymetries shallower than 500 meters, i.e., in sub-aerial to shallow marine conditions. Our work aims to confirm and extend initial results of IODP Expedition 396 from the Modgunn vent. Shallow water-depth hydrothermal venting most likely occurred during magma-rich continental breakup and NAIP emplacement; a large part of the released hydrogenic gas could have directly contributed to the global warming recorded by the PETM.
How to cite: Tugend, J., Mohn, G., Kusznir, N. J., Planke, S., Berndt, C., Zastrozhnov, D., and Millett, J. M.: Paleo-depth of hydrothermal venting along the Mid-Norwegian volcanic margin during Paleogene continental breakup, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10746, https://doi.org/10.5194/egusphere-egu25-10746, 2025.
The northeastern Brazilian rifted margin exhibits a diverse range of extensional structures, from failed onshore and offshore rifts and basins to South Atlantic seafloor spreading and continental breakup, making it an ideal natural laboratory for studying rifted margins.
Previous studies on the northeastern Brazilian rifted margin present conflicting interpretations of the basement structure in the Camamu, Almada, Jequitinhonha, Jacuípe, Sergipe, and Alagoas basins. Proposed models include: (a) hyperextended continental crust transitioning directly to oceanic crust; (b) hyperextended continental crust with exhumed lower crust and an immediate switch to oceanic crust; (c) hyperextended continental crust, exhumed mantle, and a direct transition to oceanic crust; and (d) hyperextended continental crust transitioning to proto-oceanic crust and then to normal oceanic crust. Additionally, there is ongoing debate about whether the Sergipe-Alagoas and Jequitinhonha-Almada-Camamu basins are magma-poor or more magmatic than previously thought.
The lithosphere in northeastern Brazil comprises diverse tectonic units, ranging from cratons to orogenic belts, which have undergone multiple orogenic deformations and metamorphic events. This structural and compositional heterogeneity likely exerted a first-order geologic control on the evolution of rifts, basin boundaries, and crustal structures during the opening of the South Atlantic. Analyses of basement rocks, structural trends (e.g., foliation, shear zones, and faults), and contact relationships between geologic units suggest significant geological influences on rift development.
To address these conflicting interpretations, this study adopts a thermo-mechanical approach using a newly developed numerical modeling technique, Kinedyn, which integrates seismic reflection profiles with geodynamic models. The results are expected to resolve discrepancies in previous studies and provide a more realistic reconstruction of rift evolution in the northeastern Brazilian rifted margin.
How to cite: Gün, E., Pérez-Gussinyé, M., García-Pintado, J., Gudipati, R. R., Mezri, L., and Araújo, M. N.: Geophysical, Geological, and Geodynamic Insights into the Northeastern Brazilian Rifted Margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8908, https://doi.org/10.5194/egusphere-egu25-8908, 2025.
Countless studies have been conducted in order to determine the magmatic evolution and genetic heritage of extrusive magmatic rocks associated to continental intraplate magmatism, which in case of large igneous provinces (LIPs) is frequently linked to mantle plumes associated to continental breakup and rifting. By contrast, less attention is paid to the plumbing systems of LIPs, to magma transport, storage and differentiation en route to the surface, and to the volume and composition of the plutonic portion of intraplate magmatism. Studying the origin and magmatic evolution of LIP related plutonic rocks as counterparts of more evolved extrusive series, however, provides crucial knowledge about their volume and heat budget and will have direct implications on estimates about lithospheric strength.
Here we present mineral and whole-rock geochemical and petrological data from different types of gabbros from Western Namibia which are thought to represent a deeper crustal section of a plumbing system that fed the Paranja-Etendeka LIP ~132 Ma ago. Magmatism at this time broadly coincides with Gondwana breakup and opening of the South Atlantic. Intense differentiation and cooling of larger volumes of primary mafic magmas within the lithosphere and crust might have reduced lithospheric strength and thus might have supported or even triggered continental breakup.
Major- and trace element systematics and thermodynamic modelling suggest that the gabbro parental magma developed from a tholeiitic picritic melt with up to 18wt% MgO by >10% olivine fractionation. The picritic primary magma was formed by ~14% partial mantle melting. Liquidus temperatures have been as high as ~1525°C (3 GPa) and mantle potential temperatures in the order of 1455-1470°C, significantly higher than estimates for the convecting mantle (1280-1340°C; McKenzie & Bickle, 1988) but consistent with estimates assigned to the Tristan mantle plume head upon impacting the Gondwana lithosphere (Gibson et al., 2005). Clinopyroxene trace element data reveal that the REE concentration variation between the gabbro parental magmas was nearly an order of magnitude, inconsistent with gabbro formation by pure fractional crystallization from a common magma, but in support of substantial assimilation of Pan-African continental crust accompanied by high crystallization rates. These observations imply intense heat exchange between the plumbing system and ambient lithosphere, which possibly led to marked local heating and lithosphere weakening.
McKenzie, D., Bickle, M.J., 1988, The volume and composition of melt generated by extension of the lithosphere, J. Petrol., 29, 625-679.
Gibson, S.A., Thompson, R.N., Day, J.A., Humphries, S.E., Dickin, A.P., 2005, Melt-generation processes associated with the Tristan mantle plume: Constraints on the origin of EM-1.
How to cite: Pfänder, J. A., Holaschke, P., Klügel, A., Krause, J., Jung, S., and Nagel, T.: Magmatic evolution of Paranja-Etendeka related mafic intrusive rocks in Western Namibia - impact on lithosphere heating and weakening?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17748, https://doi.org/10.5194/egusphere-egu25-17748, 2025.
The thermal and deformational history of a rift are directly correlated. Increased stretching, whether by faulting or by lower crustal flow, results in elevated heat flux, which has significant implications for the asymmetrical evolution of the heat distribution in the basins (Lescoutre et al., 2019). Since the extensional rate also controls the amount of stretching, it also becomes an important parameter for understanding the thermal evolution. In natural rift systems, acceleration is a kinematic evolution inherent to all rifting processes (Brune et al., 2016). However, the role of the extensional rate in the evolution of the thermal flux is not clear. Ten thermo-mechanical numerical models were developed using a weak and decoupled rheology for the lithosphere. The models were run with extension rates varying from 1 to 5 cm/year with intervals of 0.5 cm/year, and one model with acceleration was simulated with values estimated by Araujo et al., 2022 for the Santos-Benguela conjugates, between Brazil and Africa. Results show that the heat flux values along the widest margin of the conjugated pair increases as the constant velocity rises. In contrast to the wide margins, the narrow margins show a simple thermal evolution. The thermal evolution of the wide margin cools from the necking zone to the end of the distal domain in velocities of 2 cm/year, following the rift migration evolution. In the models with 2.5 cm/year or higher, the thermal flux evolves similarly to the deformation process described in Souza et al., 2025 - where rift migration is not well established and two rifting sites are active simultaneously. In the acceleration model, thermal flux remains high throughout the distal domain of the widest margin, driven by rift migration. In all constant velocity cases, rifting time decreases with increasing velocity, as expected. However, the acceleration model yields a rifting duration consistent with that observed in the Santos region, where the extension rates were based.
Funded by Petrobras Project 2022/00157-6.
Araujo, M. N., Pérez-Gussinyé, M., & Muldashev, I. (2023). Oceanward rift migration during formation of Santos–Benguela ultra-wide rifted margins. J. Geol. Soc. London, Special Publications.
Brune, S., Williams, S. E., Butterworth, N. P., & Müller, R. D. (2016). Abrupt plate accelerations shape rifted continental margins. Nature, 536(7615), 201-204.
Lescoutre, R., Tugend, J., Brune, S., Masini, E., & Manatschal, G. (2019). Thermal evolution of asymmetric hyperextended magma‐poor rift systems: Results from numerical modeling and Pyrenean field observations. Geochemistry, Geophysics, Geosystems, 20(10), 4567-4587.
Souza, S. dos S., Salazar-Mora, C. A., Sacek, V., & de Araujo, M. N. C. (2025). Kinematic and rheological controls on ultra-wide asymmetric rifted margins evolution. Marine and Petroleum Geology, 171, 107171.
How to cite: dos Santos Souza, S., Salazar-Mora, C. A., de Souza Bueno, J. P., Sacek, V., and Neto Cavalcanti de Araujo, M.: The Interplay Between Extensional Rate and Heat Flux in Asymmetric Rift Systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7282, https://doi.org/10.5194/egusphere-egu25-7282, 2025.
Recent studies have highlighted the impact of thermal blanketing on the evolution of rifted margins. This has been achieved by employing 2D geodynamics models in conjunction with models of superficial processes, specifically erosion and sedimentation. The findings of Andrés‐Martínez et al. (2019) and Pérez‐Gussinyé et al. (2020) demonstrate how the sediment transport can influence the architecture over geologic time and how pure ductile deformation can be caused due higher fluvial coefficients. Although this approach is more realistic and can simulate how the mass is distributed along the rifting, with the erosion of uplifted regions deposited in the local basins, it complicates parametric analysis. The deposition is highly sensitive to the input parameters of the superficial dynamics, making it difficult to establish a direct correlation between the input parameters and the outputs. For these reasons, this study aims to establish a link between the response of the margins width and architecture to the basin depths, enabling a clearer connection between the thermal blanketing, sediments thickness and the resulting architecture in a parametric approach. To reach it, a 2D thermomechanical geodynamic model was used, varying the basin thickness (2-7 km) for fixed Moho depths (35-45 km). The effects of heat flow, mechanical and thermal subsidence, and crustal thickness in the basement were analyzed, and each scenario was compared to a control model in which no varied diffusivity was assumed (there was no blanketing effect) and to a model in which no pre/syn rift basin was present. The findings are in accordance with the results of previous studies, which indicate that crustal deformation is affected by larger sediment packages, resulting in greater extension (approximately 100 km) and slower rifting (approximately 4.5 million years) compared to control scenarios. In the models with thicker sedimentary packages, the results suggest a higher thermal flux in the break-up point, with a lower heat flux in proximal domains, accompanied by an increased subsidence in the distal margin and a lower uplift in the proximal domain. The subsidence observed in the central ridge was particularly pronounced in these models with great basins, with a notable reduction in uplift along the rift shoulders.
Funded by Petrobras Project 2022/00157-6 and Brazilian National Agency for Petroleum Project PHR43.1 (2024/10598-5).
References
Andrés‐Martínez, M., Pérez‐Gussinyé, M., Armitage, J., & Morgan, J. P. (2019). Thermomechanical Implications of Sediment Transport for the Architecture and Evolution of Continental Rifts and Margins. Tectonics, 38(2), 641–665. https://doi.org/10.1029/2018TC005346
Pérez‐Gussinyé, M., Andrés‐Martínez, M., Araújo, M., Xin, Y., Armitage, J., & Morgan, J. P. (2020). Lithospheric Strength and Rift Migration Controls on Synrift Stratigraphy and Breakup Unconformities at Rifted Margins: Examples From Numerical Models, the Atlantic and South China Sea Margins. Tectonics, 39(12). https://doi.org/10.1029/2020TC006255
How to cite: Bueno, J., Sacek, V., and Paes de Almeida, R.: The impact of thermal blanketing of pre-rift basins on rifted margins subsidence and basement heat flow: Insights from 2D thermomechanical modeling., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2915, https://doi.org/10.5194/egusphere-egu25-2915, 2025.
Recent hydrocarbon discoveries in the Black Sea Basin (BSB) rekindled debate on whether the basin rifted open as one east-west oriented basin, or as two separate basins named Eastern and Western Black Sea Basins. Supporting the two-basin idea is the semi-parallel ridge and depression geometry of the BSB with NW-SE orientation in the eastern portion of the Black Sea Basin, and W-E orientation in the western portion of the Black Sea Basin. On the other hand, interpretations for a single basin configuration are supported by the regional structure of the BSB being consistent with geodynamic models of rifting of the basin by slab roll-back about a hinge point located on the eastern edge of the basin.
To help resolve the tectonic uncertainty, we built a new structural framework for the BSB by reinterpreting 24 long-offset 2D seismic lines acquired by GWL in 2011. This in turn allowed us to develop two sectioned 2D computational models representing the western and eastern parts of the BSB to model the variation in the kinematics of the basin formation. Our interpretations of continuous normal, inverted, and strike slip fault systems that define the ridge and depression geometry lead us to support a model in which the BSB opened as a single basin. The 2D sectioned models were extended to 3D to test whether the rifting occurred with increasing velocities towards west. We compare our findings with the structural elements that we interpreted on the seismic sections such as strike slip fault systems that have been active throughout the basin formation and the tectonic inversion of the Late Eocene era. Ultimately, this provides better insight of the timing of all the tectonic events of the BSB during the extensional and subsequent compressional stages of the basin’s evolution.
How to cite: Kaykun, A. and Pysklywec, R.: Structural Evolution of the Black Sea Basin Using 2D Sectioned and 3D Computational Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11717, https://doi.org/10.5194/egusphere-egu25-11717, 2025.
Normal faults and extensional detachments, their formation and migration are coupled to the formation of rifted margins, eventually leading to crustal break-up and the birth of new oceanic plates. Where and how this process occurs depends on the composition of the lithospheric layers and thus on different aspects of crustal and mantle elastic, plastic and viscous rheology. Among such indicators, the role of the shear modulus of the various lithospheric layers and thermal expansion, i.e. the relation between temperature related volume changes are not well understood. The latter, together with compressibility (i.e. the relative volume change due to pressure change), becomes particularly important during coseismic slip events, when the rock undergoes a sudden change in temperature and pressure. The influence of such parameters, under the assumption of elasticity, on continental break-up and subsequent formation of oceanic crust leading to a fully developed spreading center is still not well understood and requires further investigation.
In our study, we aim to better understand the influence of different rheological parameters (such as shear modulus, compressibility or thermal expansion), assuming a visco-elastic-plastic rheology. A particular interest lies in the contribution of elastic, plastic and viscous deformation during break up and rifting. For this purpose, we perform a series of high-resolution pseudo-2D models (i.e., models based on a fully 3D code with a shortened third dimension) based on the petrological-thermomechanical model code i3ELVIS. These models include elasto-visco-plastic rheology with strain weakening, partial mantle melting, oceanic crustal growth, thermal contraction, and mantle grain size evolution.
How to cite: Ritter, S., Balázs, A., and Gerya, T.: Decoding rheological controls on rifting and continental break-up, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16706, https://doi.org/10.5194/egusphere-egu25-16706, 2025.
Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 2
EGU25-4049 | Posters virtual | VPS28
Influence of volcanic eruptions on the sedimentary filling of a continental rift basin — A case study of the Yingcheng Formation in the Changling faulted depression in the Songliao Basin, ChinaTue, 29 Apr, 14:00–15:45 (CEST) | vP2.10
The development of continental rift basins is often accompanied by multiple episodes of volcanic activity. The impact of these volcanic eruptions on the sedimentary filling process of the basin is a geological problem worth considering. This relationship is not only the premise for reasonably explaining the binary filling characteristics and development of sequences of volcanic rocks and sedimentary rocks in rift basins but also the key geological basis for the prediction of volcanic and sedimentary rock reservoirs in rift basins. On the basis of a large amount of three-dimensional seismic data, logging data and lithology data, we estimated the volcanic eruption period, volcanic rock mass and spatial shape of the Changling faulted depression in the Songliao Basin. We then studied the spatial distribution characteristics of lithofacies and sedimentary facies in the basin. Finally, we assessed the influence of volcanic eruptions on the type of sedimentary filling, the distribution of sedimentary facies and the spatial stacking of sedimentary strata. This study revealed that during the rapid rifting stage (Yingcheng Formation depositional period), the Changling faulted depression developed mainly fan delta, braided river delta and lacustrine sedimentary systems and experienced four phases of volcanic eruptions. The lithology, scale and spatial distribution of volcanoes were directly related to the activity and location of the basement faults in this area, reflecting the control that basement fault activity had on the volcanic eruptions. Moreover, the stacking form and eruption scale of volcanic rocks played a substantial role in the paleogeomorphology of the basin, which in turn affected the form of the source channel of the basin, causing changes in the sedimentary facies type and spatial distribution and changes in the spatial overlapping pattern of the sedimentary sequence. Moreover, volcanic eruptions provided different sources of debris to the continental lake basin. The differences in location and delivery methods of these materials complicate the rock structure and reservoir properties of the basin sandstone.
How to cite: Wang, H., Zhang, H., and Liu, A.: Influence of volcanic eruptions on the sedimentary filling of a continental rift basin — A case study of the Yingcheng Formation in the Changling faulted depression in the Songliao Basin, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4049, https://doi.org/10.5194/egusphere-egu25-4049, 2025.
