We applied a series of scaled analogue experiments to investigate how the initial orientation of a single competent layer influences the development of folds and boudins in a bulk flattening strain regime. The initial angle between the competent layer and the shortening axis (θZ(i)) was systematically adjusted in 11.25° increments from 0° to 90°. As θZ(i) increased, layer thickening decreased, and the resulting structures evolved from coeval folds and boudins to predominantly tablet boudins. Folding and boudinage may be active coevally if θZ(i) < 45°, with boudin necks oriented perpendicular to the fold axes. Three distinct stages of overprinting, including folding, necking and refolding, are characteristic for one and the same run. In contrast, when θZ(i) > 45°, tablet boudins became dominant. Incremental studies indicate that the tablet boudins evolve from previous pinch-and-swell structures by tensile fractures. A striking decrease in their size and aspect ratio with progressive strain reflects strain hardening, which is also common in natural rocks. The experimental structures closely resemble natural examples found in salt rocks and other settings of bulk flattening strain.
{"title":"Coeval buckling-necking and tablet boudinage of oblique single layers in bulk flattening strain fields: Results from analogue modelling","authors":"Chao Cheng , Janet Zulauf , Gernold Zulauf , Elke Hattingen","doi":"10.1016/j.jsg.2025.105587","DOIUrl":"10.1016/j.jsg.2025.105587","url":null,"abstract":"<div><div>We applied a series of scaled analogue experiments to investigate how the initial orientation of a single competent layer influences the development of folds and boudins in a bulk flattening strain regime. The initial angle between the competent layer and the shortening axis (<em>θ</em><sub><em>Z(i)</em></sub>) was systematically adjusted in 11.25° increments from 0° to 90°. As <em>θ</em><sub><em>Z(i)</em></sub> increased, layer thickening decreased, and the resulting structures evolved from coeval folds and boudins to predominantly tablet boudins. Folding and boudinage may be active coevally if <em>θ</em><sub><em>Z(i)</em></sub> < 45°, with boudin necks oriented perpendicular to the fold axes. Three distinct stages of overprinting, including folding, necking and refolding, are characteristic for one and the same run. In contrast, when <em>θ</em><sub><em>Z(i)</em></sub> > 45°, tablet boudins became dominant. Incremental studies indicate that the tablet boudins evolve from previous pinch-and-swell structures by tensile fractures. A striking decrease in their size and aspect ratio with progressive strain reflects strain hardening, which is also common in natural rocks. The experimental structures closely resemble natural examples found in salt rocks and other settings of bulk flattening strain.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"203 ","pages":"Article 105587"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145579980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-27DOI: 10.1016/j.jsg.2025.105601
Katsushi Sato
Conventional stress tensor inversion techniques detect multiple stress conditions by minimizing misfit angles between observed fault-slip directions and calculated shear stress directions. Although this strategy is effectual for analyzing reactivated faults, frictionless faults, and faults overpressured with crustal fluids, it tends to fall into a low detectability of stress tensors because of the weak constraint. This study incorporated the fault instability (friction condition) into the objective function of stress tensor inversion for the purposes of improving the detectability and determining the friction coefficients on faults. The modified function was found to be useful to detect multiple stress and friction conditions from heterogeneous fault-slip data especially when they have concentrations of fault plane orientations. The method was applied to outcrop-scale faults cutting the Quaternary strata which filled the Beppu-Shimabara graben in the southwest Japan arc. As a result, a stress transition from ENE-WSW tension to NNE-SSW tension at ca. 1 Ma was found. The friction coefficient on faults has changed from 0.5 to 0.9, which implies a hardening of the strata through diagenesis.
{"title":"Detecting transition of stress and friction conditions by fault-slip analysis: Application to outcrop-scale faults in the Quaternary graben fill in the southwest Japan arc","authors":"Katsushi Sato","doi":"10.1016/j.jsg.2025.105601","DOIUrl":"10.1016/j.jsg.2025.105601","url":null,"abstract":"<div><div>Conventional stress tensor inversion techniques detect multiple stress conditions by minimizing misfit angles between observed fault-slip directions and calculated shear stress directions. Although this strategy is effectual for analyzing reactivated faults, frictionless faults, and faults overpressured with crustal fluids, it tends to fall into a low detectability of stress tensors because of the weak constraint. This study incorporated the fault instability (friction condition) into the objective function of stress tensor inversion for the purposes of improving the detectability and determining the friction coefficients on faults. The modified function was found to be useful to detect multiple stress and friction conditions from heterogeneous fault-slip data especially when they have concentrations of fault plane orientations. The method was applied to outcrop-scale faults cutting the Quaternary strata which filled the Beppu-Shimabara graben in the southwest Japan arc. As a result, a stress transition from ENE-WSW tension to NNE-SSW tension at ca. 1 Ma was found. The friction coefficient on faults has changed from 0.5 to 0.9, which implies a hardening of the strata through diagenesis.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"203 ","pages":"Article 105601"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145693867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-29DOI: 10.1016/j.jsg.2025.105565
Berta Vilacís , Sara Carena , Jorge N. Hayek , Gabriel Robl , Hans-Peter Bunge , Jincheng Ma
Dynamic topography is a crucial geodynamic observable that emerges as a consequence of flow in the mantle. Buoyancies associated with mantle convection induce vertical deflections at the Earth’s surface. Negative surface deflections create depositional environments and allow sedimentation to occur, while positive surface deflections create erosional/non-depositional environments, that induce gaps (hiatuses) in the geological record. The temporal and spatial extent of these gaps can be mapped using geological maps and regional studies, thus providing a means of tracking mantle processes through geological time. Here, we compare a manual and digital extraction of hiatus distributions in China. We utilise a manually compiled dataset of un/conformable contacts from a previous publication and compare it to a digital contact extraction using the recently published digital geological map of China. The digital approach is limited to surface data, whereas the manual approach allows the utilisation of subsurface information. We find that the digital approach is substantially faster than the manual extraction. Our results indicate that the optimal methodology combines digital processing with refinement of manual subsurface information. Furthermore, we observe that mapping the absence and presence of a geological series shows very similar results when processed using either approach. The current limitation to a wider application of this approach is the limited availability of digital geological maps. A standardised digital database of geological maps enhanced with subsurface information (i.e., covered geological maps) is necessary to promote the use of geological data within the wider Earth science community, and would increase the opportunities for interdisciplinary collaboration.
{"title":"Comparative analysis of manual and digital approaches for extracting geological hiatuses. A case study from China","authors":"Berta Vilacís , Sara Carena , Jorge N. Hayek , Gabriel Robl , Hans-Peter Bunge , Jincheng Ma","doi":"10.1016/j.jsg.2025.105565","DOIUrl":"10.1016/j.jsg.2025.105565","url":null,"abstract":"<div><div>Dynamic topography is a crucial geodynamic observable that emerges as a consequence of flow in the mantle. Buoyancies associated with mantle convection induce vertical deflections at the Earth’s surface. Negative surface deflections create depositional environments and allow sedimentation to occur, while positive surface deflections create erosional/non-depositional environments, that induce gaps (hiatuses) in the geological record. The temporal and spatial extent of these gaps can be mapped using geological maps and regional studies, thus providing a means of tracking mantle processes through geological time. Here, we compare a manual and digital extraction of hiatus distributions in China. We utilise a manually compiled dataset of un/conformable contacts from a previous publication and compare it to a digital contact extraction using the recently published digital geological map of China. The digital approach is limited to surface data, whereas the manual approach allows the utilisation of subsurface information. We find that the digital approach is substantially faster than the manual extraction. Our results indicate that the optimal methodology combines digital processing with refinement of manual subsurface information. Furthermore, we observe that mapping the absence and presence of a geological series shows very similar results when processed using either approach. The current limitation to a wider application of this approach is the limited availability of digital geological maps. A standardised digital database of geological maps enhanced with subsurface information (i.e., covered geological maps) is necessary to promote the use of geological data within the wider Earth science community, and would increase the opportunities for interdisciplinary collaboration.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105565"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145425875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work describes how flexural normal faults related to a flexure produced in the foredeep of a fold-and-thrust belt develop, how they can be recognized, especially when they formed in early or intermediate stages of development of the fold-and-thrust belt, what information provide about the fold-and-thrust belt and the foredeep flexure, and different procedures to obtain it. The application of these methodologies to a natural example is shown through the detailed analysis of normal faults preceding the folds and thrusts in the western part of the Cantabrian Zone, the foreland fold-and-thrust belt of the Variscan Orogen in the northwest portion of the Iberian Peninsula. These faults are interpreted as flexural normal faults formed during the fold-and-thrust belt development. The strike of the longitudinal flexural normal faults illustrates the orientation of the old fold-and-thrust belt front, resulting in an arcuate distribution consistent with the geometry of the Ibero-Armorican or Asturian Arc. The low fracturing intensity due to the longitudinal faults indicates that the flexure curvature and the flexure inclined-limb dip were very gentle, and that the flexure interlimb angle was very high. This may suggest that the fold-and-thrust belt weight was low at that time. The timing of these flexural normal faults indicate that the thrusts propagated following a forward-breaking or “piggy-back” sequence, as deduced by other authors employing different methods. Finally, the transverse flexural normal faults are interpreted as a result of large oblique/lateral thrust ramps in some thrust sheets located in the southern part of the Cantabrian Zone.
{"title":"What do flexural normal faults tell us about fold-and-thrust belts and foredeep flexures? Cantabrian zone (Ibero-Armorican Orocline core) examples","authors":"Mayte Bulnes , Hodei Uzkeda , Josep Poblet , Iván García Zuazua","doi":"10.1016/j.jsg.2025.105564","DOIUrl":"10.1016/j.jsg.2025.105564","url":null,"abstract":"<div><div>This work describes how flexural normal faults related to a flexure produced in the foredeep of a fold-and-thrust belt develop, how they can be recognized, especially when they formed in early or intermediate stages of development of the fold-and-thrust belt, what information provide about the fold-and-thrust belt and the foredeep flexure, and different procedures to obtain it. The application of these methodologies to a natural example is shown through the detailed analysis of normal faults preceding the folds and thrusts in the western part of the Cantabrian Zone, the foreland fold-and-thrust belt of the Variscan Orogen in the northwest portion of the Iberian Peninsula. These faults are interpreted as flexural normal faults formed during the fold-and-thrust belt development. The strike of the longitudinal flexural normal faults illustrates the orientation of the old fold-and-thrust belt front, resulting in an arcuate distribution consistent with the geometry of the Ibero-Armorican or Asturian Arc. The low fracturing intensity due to the longitudinal faults indicates that the flexure curvature and the flexure inclined-limb dip were very gentle, and that the flexure interlimb angle was very high. This may suggest that the fold-and-thrust belt weight was low at that time. The timing of these flexural normal faults indicate that the thrusts propagated following a forward-breaking or “piggy-back” sequence, as deduced by other authors employing different methods. Finally, the transverse flexural normal faults are interpreted as a result of large oblique/lateral thrust ramps in some thrust sheets located in the southern part of the Cantabrian Zone.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105564"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145369810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-06DOI: 10.1016/j.jsg.2025.105566
Jasemin Ayse Ölmez, Benjamin Busch, Christoph Hilgers
Understanding structural and diagenetic interactions is key in analyzing flow pathways in tight lithologies in the focus of geo-energy production as e.g., geothermal energy. Fracture spacing and clustering is crucial for reservoir production success and reduces uncertainty in reservoir exploration and utilization. This outcrop analog study evaluates diagenesis, fractures, vein cement generations, kink bands, and faults in tight fractured limestones of the Upper Muschelkalk-Lower Keuper transition on the eastern Upper Rhine Graben shoulder in SW Germany. Early and burial diagenesis led to cementation of former pore spaces and therefore drastically reduced the matrix porosity and permeability (porosity: 0.13–10.87 %, permeability: <0.0001 mD to 9.7 mD). Highest permeabilities are recorded in samples containing partially sealed veins and stylolites (up to 9.7 mD) at 1.2 MPa confining stress. The impact of increasing confining stress on the permeability of undisturbed limestones, as well as limestones containing stylolites and partially sealed veins, indicate that besides an undisturbed host rock sample and a sample containing stylolites, partially sealed veins preserve higher permeability at 30 MPa confining stress (41 % of initial value, compared to 16 and 11 % of the initial value).
Fracture cluster analyses using the normalized correlation count method indicates that clustering around a breached kink band and associated fault is not symmetrically arranged and contains fracture sets of different strike. Fracture clusters also exist away from the fault at the breached kink band. Slip and dilation tendencies indicate that clustered fracture sets striking NNE-SSW parallel to the Rhine graben rift, WNW-ESE, and NW-SE parallel to the in-situ maximum principal horizontal stress are more likely to contribute to fluid flow as they are suitably oriented in the present-day stress field. Breached, decameter-scale reverse kink bands are the first reported in the region, c. 180–200 km N-NNE of the Alpine deformation front. Kink bands are most likely related to compression by far field stresses induced by the Alpine orogeny during the Eocene, and show partially cemented fault planes indicating locally persevered pore space.
The applied methods of structural and diagenetic reservoir quality assessment and obtained outcomes aid in the understanding of fluid migration pathways for geoenergy applications in the Upper Rhine Graben area. Further, the results are also transferrable to other fractured tight reservoirs worldwide, which can help to solve problems for energy or heat supply that are of societal importance.
{"title":"Structural and diagenetic controls on flow pathways in fractured Triassic Muschelkalk and Keuper limestones, southern Germany – Implications for geoenergy exploration","authors":"Jasemin Ayse Ölmez, Benjamin Busch, Christoph Hilgers","doi":"10.1016/j.jsg.2025.105566","DOIUrl":"10.1016/j.jsg.2025.105566","url":null,"abstract":"<div><div>Understanding structural and diagenetic interactions is key in analyzing flow pathways in tight lithologies in the focus of geo-energy production as e.g., geothermal energy. Fracture spacing and clustering is crucial for reservoir production success and reduces uncertainty in reservoir exploration and utilization. This outcrop analog study evaluates diagenesis, fractures, vein cement generations, kink bands, and faults in tight fractured limestones of the Upper Muschelkalk-Lower Keuper transition on the eastern Upper Rhine Graben shoulder in SW Germany. Early and burial diagenesis led to cementation of former pore spaces and therefore drastically reduced the matrix porosity and permeability (porosity: 0.13–10.87 %, permeability: <0.0001 mD to 9.7 mD). Highest permeabilities are recorded in samples containing partially sealed veins and stylolites (up to 9.7 mD) at 1.2 MPa confining stress. The impact of increasing confining stress on the permeability of undisturbed limestones, as well as limestones containing stylolites and partially sealed veins, indicate that besides an undisturbed host rock sample and a sample containing stylolites, partially sealed veins preserve higher permeability at 30 MPa confining stress (41 % of initial value, compared to 16 and 11 % of the initial value).</div><div>Fracture cluster analyses using the normalized correlation count method indicates that clustering around a breached kink band and associated fault is not symmetrically arranged and contains fracture sets of different strike. Fracture clusters also exist away from the fault at the breached kink band. Slip and dilation tendencies indicate that clustered fracture sets striking NNE-SSW parallel to the Rhine graben rift, WNW-ESE, and NW-SE parallel to the in-situ maximum principal horizontal stress are more likely to contribute to fluid flow as they are suitably oriented in the present-day stress field. Breached, decameter-scale reverse kink bands are the first reported in the region, c. 180–200 km N-NNE of the Alpine deformation front. Kink bands are most likely related to compression by far field stresses induced by the Alpine orogeny during the Eocene, and show partially cemented fault planes indicating locally persevered pore space.</div><div>The applied methods of structural and diagenetic reservoir quality assessment and obtained outcomes aid in the understanding of fluid migration pathways for geoenergy applications in the Upper Rhine Graben area. Further, the results are also transferrable to other fractured tight reservoirs worldwide, which can help to solve problems for energy or heat supply that are of societal importance.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105566"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145529363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-06DOI: 10.1016/j.jsg.2025.105570
Anis Khalifeh-Soltani , Seyed Ahmad Alavi , Reza Derakhshani
Strike-slip faults are fundamental tectonic structures that exert a major influence on both seismic activity and hydrocarbon reservoir development. However, the geometric evolution and internal deformation mechanisms of contractional and extensional strike-slip duplexes remain poorly understood. This study employs five three-dimensional finite element models in Abaqus to investigate how variations in the convergence angle of the main strike-slip fault control the geometry, deformation pattern, and stress distribution within duplex systems. The results demonstrate that fault-scarp development and internal deformation are strongly governed by the convergence angle and by the presence of duplex structures. The most pronounced geometric changes occur at zero-degree convergence, where displacement is parallel to the fault plane, producing dominant pure-shear deformation rather than simple shear. The strain ellipse patterns in both extensional and contractional duplexes correspond closely to those of transtensional and transpressional strike-slip zones. The models also show that oblique convergence and duplex formation significantly amplify local stress and strain concentrations, indicating that duplexes can act as potential sites of rupture initiation. Moreover, under identical geological conditions, contractional and extensional duplexes reach critical stress levels earlier than simple strike-slip faults, implying shorter earthquake recurrence intervals. These findings advance the understanding of scarp formation, deformation partitioning, and stress localization in strike-slip duplexes, with important implications for seismic hazard assessment and for predicting hydrocarbon migration and entrapment in structurally complex fault systems.
{"title":"Evaluating the role of convergence angle in the geometry of contractional and extensional strike-slip duplexes using 3D finite element models","authors":"Anis Khalifeh-Soltani , Seyed Ahmad Alavi , Reza Derakhshani","doi":"10.1016/j.jsg.2025.105570","DOIUrl":"10.1016/j.jsg.2025.105570","url":null,"abstract":"<div><div>Strike-slip faults are fundamental tectonic structures that exert a major influence on both seismic activity and hydrocarbon reservoir development. However, the geometric evolution and internal deformation mechanisms of contractional and extensional strike-slip duplexes remain poorly understood. This study employs five three-dimensional finite element models in Abaqus to investigate how variations in the convergence angle of the main strike-slip fault control the geometry, deformation pattern, and stress distribution within duplex systems. The results demonstrate that fault-scarp development and internal deformation are strongly governed by the convergence angle and by the presence of duplex structures. The most pronounced geometric changes occur at zero-degree convergence, where displacement is parallel to the fault plane, producing dominant pure-shear deformation rather than simple shear. The strain ellipse patterns in both extensional and contractional duplexes correspond closely to those of transtensional and transpressional strike-slip zones. The models also show that oblique convergence and duplex formation significantly amplify local stress and strain concentrations, indicating that duplexes can act as potential sites of rupture initiation. Moreover, under identical geological conditions, contractional and extensional duplexes reach critical stress levels earlier than simple strike-slip faults, implying shorter earthquake recurrence intervals. These findings advance the understanding of scarp formation, deformation partitioning, and stress localization in strike-slip duplexes, with important implications for seismic hazard assessment and for predicting hydrocarbon migration and entrapment in structurally complex fault systems.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105570"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145528927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-21DOI: 10.1016/j.jsg.2025.105561
G.I. Alsop , S. Marco , R. Weinberger , T. Levi
<div><div>Although detachments form an integral component of gravity-driven downslope movement, their largely bed-parallel nature can make them difficult to identify in both seismic and outcrop studies. Sediments above bed-parallel detachments (BPDs) associated with intra-stratal deformation are carried passively downslope and therefore represent a form of mass transport deposit (MTD). Using outcrop examples of MTDs created in late-Pleistocene lacustrine sediments around the Dead Sea, we present a catalogue of exceptional extensional and contractional structures generated along BPDs. Detachments may form individual structures that locally ramp to higher structural levels, creating extensional ramps in the upslope direction and contractional ramps further downslope. Alternatively, detachments may comprise multiple strands that kinematically interact with one another via ‘soft-linkage’, or are geometrically coupled via connecting faults to create a ‘hard-linkage’. Lower detachments involving multiple slip surfaces interact with one another to create localised extensional and contractional duplexes, whilst collectively forming the base of the slide sheet. Upper detachments may consist of several strands, or alternatively form ‘soft-linked detachments’ where deformation is distributed across units with no discrete slip surface. Thrusts above detachments frequently follow a ‘piggyback’ sequence with younger shallower thrusts displaying less overall shortening forming downslope of older steeper imbricates. This suggests that they are formed during downslope migration of the duplex rather than upslope propagation of compressive strain during ‘locking up’ of gravity-driven deformation. The fields of extensional and contractional strain may expand and change location during evolution of the slide, leading to normal faults and thrust faults locally overprinting one another. In addition, thrust and normal faults may operate coevally, or locally reactivate one another during positive and negative inversion of individual structures. Transfer of BPD displacement to different levels is achieved by local ramping across older normal and thrust faults, resulting in significant changes to the stratigraphic position of BPDs, together with notable variations in heave across fault zones. Movement on the BPDs is facilitated by high fluid pressures that create sediment injections along the slide planes, especially where normal faults intersect the lower detachment. Where multiple BPDs are formed along the lower detachment, sediment injections cut the upper detachment, suggesting that deformation and movement was longer-lived along the lowermost BPD in a system. Overall, the observation that all measured BPDs (N > 170) consistently display a top-towards the basin sense of displacement suggests that they were sequentially developed through the sediment pile during numerous slope failures, rather than forming synchronously in a single major event that could lead to loca
{"title":"A catalogue of extensional and contractional structures generated along gravity-driven detachments","authors":"G.I. Alsop , S. Marco , R. Weinberger , T. Levi","doi":"10.1016/j.jsg.2025.105561","DOIUrl":"10.1016/j.jsg.2025.105561","url":null,"abstract":"<div><div>Although detachments form an integral component of gravity-driven downslope movement, their largely bed-parallel nature can make them difficult to identify in both seismic and outcrop studies. Sediments above bed-parallel detachments (BPDs) associated with intra-stratal deformation are carried passively downslope and therefore represent a form of mass transport deposit (MTD). Using outcrop examples of MTDs created in late-Pleistocene lacustrine sediments around the Dead Sea, we present a catalogue of exceptional extensional and contractional structures generated along BPDs. Detachments may form individual structures that locally ramp to higher structural levels, creating extensional ramps in the upslope direction and contractional ramps further downslope. Alternatively, detachments may comprise multiple strands that kinematically interact with one another via ‘soft-linkage’, or are geometrically coupled via connecting faults to create a ‘hard-linkage’. Lower detachments involving multiple slip surfaces interact with one another to create localised extensional and contractional duplexes, whilst collectively forming the base of the slide sheet. Upper detachments may consist of several strands, or alternatively form ‘soft-linked detachments’ where deformation is distributed across units with no discrete slip surface. Thrusts above detachments frequently follow a ‘piggyback’ sequence with younger shallower thrusts displaying less overall shortening forming downslope of older steeper imbricates. This suggests that they are formed during downslope migration of the duplex rather than upslope propagation of compressive strain during ‘locking up’ of gravity-driven deformation. The fields of extensional and contractional strain may expand and change location during evolution of the slide, leading to normal faults and thrust faults locally overprinting one another. In addition, thrust and normal faults may operate coevally, or locally reactivate one another during positive and negative inversion of individual structures. Transfer of BPD displacement to different levels is achieved by local ramping across older normal and thrust faults, resulting in significant changes to the stratigraphic position of BPDs, together with notable variations in heave across fault zones. Movement on the BPDs is facilitated by high fluid pressures that create sediment injections along the slide planes, especially where normal faults intersect the lower detachment. Where multiple BPDs are formed along the lower detachment, sediment injections cut the upper detachment, suggesting that deformation and movement was longer-lived along the lowermost BPD in a system. Overall, the observation that all measured BPDs (N > 170) consistently display a top-towards the basin sense of displacement suggests that they were sequentially developed through the sediment pile during numerous slope failures, rather than forming synchronously in a single major event that could lead to loca","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105561"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145425877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a multiscale interpretation of faults and their damage zones in the subsurface, consisting of subseismic faults and deformation bands (DB), in the Upper Rotliegend deposits, in the Polish part of the Southern Permian Basin, using a multiscale approach, integrating seismic and well data. Full-bandwidth and high-frequency seismic data, utilising spectral decomposition, were used to interpret the main and minor (small) faults, respectively. Seismic attributes and deep convolutional neural network (DNN) fault volumes were used to improve the interpretation and fault geometric characterization. Faults were visualised and mapped by both DNN and ant tracking analyses, while DNN indicates higher fault probability and continuity. The study area displays two fault trends: a dominant NW–SE trend, initially formed during the basin extension, and a secondary NE–SW trend, formed during the basin inversion, which is more clearly visible in high-frequency component. Well data, resistivity image logs supported by gamma ray logs and well cores, allowed us to identify and map DBs and their connection with fault damage zones. The number of DB increases with faults' proximity, throw and in dune and interdune sandstones.
Investigation of the basin geomorphology and the depositional environments provided insights into the multistage tectonic evolution, which has influenced fault displacement and damage zone geometry and extent. Despite the uncertainties in the data, a positive correlation between fault length and throw (fault scaling law) is evident, which can be further used to strengthen our prediction of fault geometric attributes.
{"title":"Multiscale subsurface structural study – insights from the polish part of the Southern Permian Basin","authors":"Weronika Mikołajewska , Anita Torabi , Edyta Puskarczyk","doi":"10.1016/j.jsg.2025.105568","DOIUrl":"10.1016/j.jsg.2025.105568","url":null,"abstract":"<div><div>We present a multiscale interpretation of faults and their damage zones in the subsurface, consisting of subseismic faults and deformation bands (DB), in the Upper Rotliegend deposits, in the Polish part of the Southern Permian Basin, using a multiscale approach, integrating seismic and well data. Full-bandwidth and high-frequency seismic data, utilising spectral decomposition, were used to interpret the main and minor (small) faults, respectively. Seismic attributes and deep convolutional neural network (DNN) fault volumes were used to improve the interpretation and fault geometric characterization. Faults were visualised and mapped by both DNN and ant tracking analyses, while DNN indicates higher fault probability and continuity. The study area displays two fault trends: a dominant NW–SE trend, initially formed during the basin extension, and a secondary NE–SW trend, formed during the basin inversion, which is more clearly visible in high-frequency component. Well data, resistivity image logs supported by gamma ray logs and well cores, allowed us to identify and map DBs and their connection with fault damage zones. The number of DB increases with faults' proximity, throw and in dune and interdune sandstones.</div><div>Investigation of the basin geomorphology and the depositional environments provided insights into the multistage tectonic evolution, which has influenced fault displacement and damage zone geometry and extent. Despite the uncertainties in the data, a positive correlation between fault length and throw (fault scaling law) is evident, which can be further used to strengthen our prediction of fault geometric attributes.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105568"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145528925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-10-22DOI: 10.1016/j.jsg.2025.105563
A. Luppino , F.L. Bonali , A. Gudmundsson , A. Tibaldi
To better understand the conditions and mechanisms under which dikes interact with pre-existing vertical fractures, we analyzed the fracture swarm and volcanic vents developed during the 1947 eruption (North-East Rift, Etna), and reconstructed the pre-1947 fracture field by historical aerial photos. Then we developed Finite Element Method numerical models, varying the number, spacing, width and vertical and lateral distance of pre-existing fractures with respect to a dike, as well as the dike overpressure. Although in general the 1947 dike followed the path of a previous dike, at a more detailed scale the 1947 vents are shifted up to 11 m laterally with respect to the nearest pre-existing fracture. In areas where few fractures were already present, a significant number of new fractures developed during the 1947 event, whereas if several fractures pre-existed, a few new ones formed. In the case of a pre-existent single fracture, numerical models suggest two scenarios: nucleation of a new fracture bending toward the pre-existing one, possibly followed by dike deflection, or the vertical propagation of the dike. The latter is facilitated by close pre-existing fractures, because dike/fracture interaction enhances tensile stress above the dike tip. This stress increase is sensitive to horizontal fracture spacing, dike/fracture depth difference, and dike overpressure. Stress concentration towards the dike tip and fracture base means a lower probability of new fractures formation at the surface if pre-existing fractures are already widespread. A dike located nearby, or in the middle, of already existing fractures, receives a stress “booster” enhancing its probability of further propagation.
{"title":"Effects of pre-existing fractures on dike propagation: new insights from field data and numerical modelling","authors":"A. Luppino , F.L. Bonali , A. Gudmundsson , A. Tibaldi","doi":"10.1016/j.jsg.2025.105563","DOIUrl":"10.1016/j.jsg.2025.105563","url":null,"abstract":"<div><div>To better understand the conditions and mechanisms under which dikes interact with pre-existing vertical fractures, we analyzed the fracture swarm and volcanic vents developed during the 1947 eruption (North-East Rift, Etna), and reconstructed the pre-1947 fracture field by historical aerial photos. Then we developed Finite Element Method numerical models, varying the number, spacing, width and vertical and lateral distance of pre-existing fractures with respect to a dike, as well as the dike overpressure. Although in general the 1947 dike followed the path of a previous dike, at a more detailed scale the 1947 vents are shifted up to 11 m laterally with respect to the nearest pre-existing fracture. In areas where few fractures were already present, a significant number of new fractures developed during the 1947 event, whereas if several fractures pre-existed, a few new ones formed. In the case of a pre-existent single fracture, numerical models suggest two scenarios: nucleation of a new fracture bending toward the pre-existing one, possibly followed by dike deflection, or the vertical propagation of the dike. The latter is facilitated by close pre-existing fractures, because dike/fracture interaction enhances tensile stress above the dike tip. This stress increase is sensitive to horizontal fracture spacing, dike/fracture depth difference, and dike overpressure. Stress concentration towards the dike tip and fracture base means a lower probability of new fractures formation at the surface if pre-existing fractures are already widespread. A dike located nearby, or in the middle, of already existing fractures, receives a stress “booster” enhancing its probability of further propagation.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105563"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145425876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-10DOI: 10.1016/j.jsg.2025.105583
Riccardo Sordi , Spyridon Saltapidas , Adrian Hartley , Mark Cooper
Understanding the rates and amount of extension during the initiation of rifting in the northern North Sea basin is important for defining the structural framework for the subsequent Mesozoic rifting event. The pre-Jurassic tectonic history of the northern North Sea rift has, to date, been largely overlooked due to difficulties in distinguishing Triassic strata from older Devonian and Permian units, limited quality of deep seismic data and a lack of deep well penetrations within rift basin depocenters. This study integrates recent research on the Triassic of the North Sea region to analyse and restore 2D seismic lines and establish a unified tectonic framework for the northern North Sea Triassic rift system. Four regional transects and nine sections covering the Norwegian and UK sectors are analysed, and the tectonic stretching is calculated for the Devonian-Carboniferous, Permian, Triassic (Early, Middle, and Late), Jurassic, and Cretaceous. Our results demonstrate that during the Triassic, extension occurred primarily in the Early and Late Triassic, with minor extension in the Middle Triassic. Furthermore, the Triassic rift was a significantly lower-magnitude event than previously estimated (between β = 1.20 and 1.50), with an extension of c.a. 4 % (β = 1.04). By utilising cross-border datasets, this work reviews the northern North Sea stretching factor throughout the upper Paleozoic and Mesozoic. It also provides a comparative analysis with other rifts, exploring the evolution of the northern North Sea and its relationship with the opening of the Atlantic, ultimately creating a cohesive narrative of the Mesozoic rifting event and its earlier evolutionary stages.
{"title":"A quantitative assessment of tectonic stretching in the northern North Sea, the Triassic of the Utsira High and greater Tampen Spur area","authors":"Riccardo Sordi , Spyridon Saltapidas , Adrian Hartley , Mark Cooper","doi":"10.1016/j.jsg.2025.105583","DOIUrl":"10.1016/j.jsg.2025.105583","url":null,"abstract":"<div><div>Understanding the rates and amount of extension during the initiation of rifting in the northern North Sea basin is important for defining the structural framework for the subsequent Mesozoic rifting event. The pre-Jurassic tectonic history of the northern North Sea rift has, to date, been largely overlooked due to difficulties in distinguishing Triassic strata from older Devonian and Permian units, limited quality of deep seismic data and a lack of deep well penetrations within rift basin depocenters. This study integrates recent research on the Triassic of the North Sea region to analyse and restore 2D seismic lines and establish a unified tectonic framework for the northern North Sea Triassic rift system. Four regional transects and nine sections covering the Norwegian and UK sectors are analysed, and the tectonic stretching is calculated for the Devonian-Carboniferous, Permian, Triassic (Early, Middle, and Late), Jurassic, and Cretaceous. Our results demonstrate that during the Triassic, extension occurred primarily in the Early and Late Triassic, with minor extension in the Middle Triassic. Furthermore, the Triassic rift was a significantly lower-magnitude event than previously estimated (between β = 1.20 and 1.50), with an extension of c.a. 4 % (β = 1.04). By utilising cross-border datasets, this work reviews the northern North Sea stretching factor throughout the upper Paleozoic and Mesozoic. It also provides a comparative analysis with other rifts, exploring the evolution of the northern North Sea and its relationship with the opening of the Atlantic, ultimately creating a cohesive narrative of the Mesozoic rifting event and its earlier evolutionary stages.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105583"},"PeriodicalIF":2.9,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145528923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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