Pub Date : 2025-11-13DOI: 10.1016/j.jsg.2025.105560
Hugues Raimbourg , Benjamin Moris-Muttoni , Romain Augier , Kristijan Rajič , Ismay Vénice Akker , Aurélien Canizarès , Emmanuel Le Trong
Carbonaceous matter is a common component of metasedimentary rocks, mainly deriving from the diagenetic and then metamorphic evolution of the organic matter originally present in the sedimentary protolith. During burial, the maturity of carbonaceous particles increases by rearrangements of the aromatic carbon sheets and expulsion of heteroatoms, mostly as a result of temperature increase. However, additional external factors could enhance the maturity such as the pressure, fluid-rock interactions and/or deformation. In this work we explored the effect of strain at low metamorphic temperatures (in the range ∼200–320 °C) along natural strain gradients of variable scales, in three accretionary or collisional complexes (Shimanto and Kodiak accretionary complexes, Infrahelvetic Flysch Units), using Raman spectra of carbonaceous matter. In these examples, both ductile and brittle zones of localized deformation were observed, in the form of shear and breccia zones, respectively. Carbonaceous particles observed by TEM are ∼50–100 nm in size and are distributed throughout the rocks, enabling automated Raman spectroscopy profiles and maps to be carried out. Irrespective of the deformation process, the intensity ratio between D and G band (R1 ratio) of Raman spectra is systematically increased by up to ∼60 % in high strain zones compared to the least deformed, reference zones. From the comparison with a series of undeformed metamorphic rocks spanning the same temperature range, the R1 increase reflects the progressive organization of the carbonaceous matter towards higher maturity. In mm-scale shear bands, the increase in R1 can be unambiguously ascribed to localized strain, whereas in brecciated domains, localized temperature increase may also have contributed to R1 anomaly.
{"title":"Impact of strain on carbonaceous matter crystallinity: Insights from Raman spectroscopy and microstructural analysis of strain gradients from exhumed accretionary complexes","authors":"Hugues Raimbourg , Benjamin Moris-Muttoni , Romain Augier , Kristijan Rajič , Ismay Vénice Akker , Aurélien Canizarès , Emmanuel Le Trong","doi":"10.1016/j.jsg.2025.105560","DOIUrl":"10.1016/j.jsg.2025.105560","url":null,"abstract":"<div><div>Carbonaceous matter is a common component of metasedimentary rocks, mainly deriving from the diagenetic and then metamorphic evolution of the organic matter originally present in the sedimentary protolith. During burial, the maturity of carbonaceous particles increases by rearrangements of the aromatic carbon sheets and expulsion of heteroatoms, mostly as a result of temperature increase. However, additional external factors could enhance the maturity such as the pressure, fluid-rock interactions and/or deformation. In this work we explored the effect of strain at low metamorphic temperatures (in the range ∼200–320 °C) along natural strain gradients of variable scales, in three accretionary or collisional complexes (Shimanto and Kodiak accretionary complexes, Infrahelvetic Flysch Units), using Raman spectra of carbonaceous matter. In these examples, both ductile and brittle zones of localized deformation were observed, in the form of shear and breccia zones, respectively. Carbonaceous particles observed by TEM are ∼50–100 nm in size and are distributed throughout the rocks, enabling automated Raman spectroscopy profiles and maps to be carried out. Irrespective of the deformation process, the intensity ratio between D and G band (R1 ratio) of Raman spectra is systematically increased by up to ∼60 % in high strain zones compared to the least deformed, reference zones. From the comparison with a series of undeformed metamorphic rocks spanning the same temperature range, the R1 increase reflects the progressive organization of the carbonaceous matter towards higher maturity. In mm-scale shear bands, the increase in R1 can be unambiguously ascribed to localized strain, whereas in brecciated domains, localized temperature increase may also have contributed to R1 anomaly.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"203 ","pages":"Article 105560"},"PeriodicalIF":2.9,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145580011","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 : 2025-11-12DOI: 10.1016/j.jsg.2025.105584
Eloi González-Esvertit , Josep Maria Casas , Àngels Canals , Paul D. Bons , Kevin Konrad , Maria-Gema Llorens , Gabriel Serrano-López , Claudia Prieto-Torrell , Joyce Neilson , Diego Domínguez-Carretero , Aratz Beranoaguirre , Axel Gerdes , Enrique Gomez-Rivas
The age of the mylonite belts in the basement rocks of the Pyrenees is a subject of debate in the structural geology and petrology communities because of its potential implication on the regional tectonothermal history and on the tectonic evolution of SW Europe. Here we address when and how mylonitisation took place in two key areas of the Eastern Pyrenees, where shear zones are associated with Giant Quartz Veins (GQVs). We conducted zircon U-Pb and muscovite 40Ar/39Ar dating coupled with structural, textural, and crystallographic preferred orientation (CPO) analyses of mylonites from the Cap de Creus and Canigó Massifs. U-Pb zircon dating of a dacite porphyry dyke crosscut by GQVs and mylonitic bands yields a maximum shear zone and GQV formation age of ca. 292 ± 3 Ma. 40Ar/39Ar analyses of muscovite within mylonitised GQVs yield initial crystallisation ages between ca. 164 and 188 Ma, as well as younger recrystallisation ages of ca. 110–118 Ma. A qualitative assessment of the GQV history is inferred from step-heating spectra of muscovite and quartz CPOs. The results indicate that GQV formation and mylonitisation were coupled, coeval, and long-lasting processes that took place from early Jurassic to early Cretaceous times. A comparative evaluation of quartz CPOs reveals inconsistencies regarding the strain distribution, quartz slip systems activity, and deformation temperatures depending on the deformed rock type. Quartz mylonites have stronger CPOs dominated by basal <a>, prism <a>, or prism <c> slip systems, whilst phyllonites and granite mylonites show weaker fabrics mostly dominated by mixed <a> slip. This apparently suggests higher deformation temperatures in quartz mylonites than those inferred from more reliable proxies, such as mineral assemblages, brittle behaviour of K-feldspar, and fluid inclusion data. We suggest that the water-weakening effect caused by coeval formation and deformation of GQVs enabled easier dislocation glide and creep, allowing strain localisation and transitions between slip systems at lower temperatures than commonly inferred due to enhanced ductility. U-Pb zircon dating further suggests the existence of an early Carboniferous (ca. 332 ± 4 Ma; Visean) magmatic episode in the Pyrenees, in agreement with a cyclic, rather than a progressive, geodynamic history of the region during Variscan times. The present work challenges classical interpretations stating that Pyrenean mylonite belts developed during the retrograde stages of the Variscan Orogeny, highlighting that the structural evolution of this region during Mesozoic times deserves further investigation. Results have implications for interpreting deformation localisation mechanisms and conditions in crustal rocks, for the formation mechanisms of GQVs in worldwide orogenic belts, and for the tectonothermal history of the Pyrenees since late-Variscan times.
{"title":"Hydrolytic weakening controls Jurassic to early Cretaceous mylonitisation in the basement of the Pyrenees","authors":"Eloi González-Esvertit , Josep Maria Casas , Àngels Canals , Paul D. Bons , Kevin Konrad , Maria-Gema Llorens , Gabriel Serrano-López , Claudia Prieto-Torrell , Joyce Neilson , Diego Domínguez-Carretero , Aratz Beranoaguirre , Axel Gerdes , Enrique Gomez-Rivas","doi":"10.1016/j.jsg.2025.105584","DOIUrl":"10.1016/j.jsg.2025.105584","url":null,"abstract":"<div><div>The age of the mylonite belts in the basement rocks of the Pyrenees is a subject of debate in the structural geology and petrology communities because of its potential implication on the regional tectonothermal history and on the tectonic evolution of SW Europe. Here we address when and how mylonitisation took place in two key areas of the Eastern Pyrenees, where shear zones are associated with Giant Quartz Veins (GQVs). We conducted zircon U-Pb and muscovite <sup>40</sup>Ar/<sup>39</sup>Ar dating coupled with structural, textural, and crystallographic preferred orientation (CPO) analyses of mylonites from the Cap de Creus and Canigó Massifs. U-Pb zircon dating of a dacite porphyry dyke crosscut by GQVs and mylonitic bands yields a maximum shear zone and GQV formation age of ca. 292 ± 3 Ma. <sup>40</sup>Ar/<sup>39</sup>Ar analyses of muscovite within mylonitised GQVs yield initial crystallisation ages between ca. 164 and 188 Ma, as well as younger recrystallisation ages of ca. 110–118 Ma. A qualitative assessment of the GQV history is inferred from step-heating spectra of muscovite and quartz CPOs. The results indicate that GQV formation and mylonitisation were coupled, coeval, and long-lasting processes that took place from early Jurassic to early Cretaceous times. A comparative evaluation of quartz CPOs reveals inconsistencies regarding the strain distribution, quartz slip systems activity, and deformation temperatures depending on the deformed rock type. Quartz mylonites have stronger CPOs dominated by basal <a>, prism <a>, or prism <c> slip systems, whilst phyllonites and granite mylonites show weaker fabrics mostly dominated by mixed <a> slip. This apparently suggests higher deformation temperatures in quartz mylonites than those inferred from more reliable proxies, such as mineral assemblages, brittle behaviour of K-feldspar, and fluid inclusion data. We suggest that the water-weakening effect caused by coeval formation and deformation of GQVs enabled easier dislocation glide and creep, allowing strain localisation and transitions between slip systems at lower temperatures than commonly inferred due to enhanced ductility. U-Pb zircon dating further suggests the existence of an early Carboniferous (ca. 332 ± 4 Ma; Visean) magmatic episode in the Pyrenees, in agreement with a cyclic, rather than a progressive, geodynamic history of the region during Variscan times. The present work challenges classical interpretations stating that Pyrenean mylonite belts developed during the retrograde stages of the Variscan Orogeny, highlighting that the structural evolution of this region during Mesozoic times deserves further investigation. Results have implications for interpreting deformation localisation mechanisms and conditions in crustal rocks, for the formation mechanisms of GQVs in worldwide orogenic belts, and for the tectonothermal history of the Pyrenees since late-Variscan times.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"203 ","pages":"Article 105584"},"PeriodicalIF":2.9,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145693865","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 : 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":"2025-11-10","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}
Pub 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":"2025-11-06","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 : 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":"2025-11-06","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 : 2025-11-06DOI: 10.1016/j.jsg.2025.105567
Javed N. Malik , Mitthu Dhali , Mahendrasinh S. Gadhavi , Prabhat Kumar , Eshaan Srivastava , Mohd Azhar Ansari , Nayan Sharma , Santiswarup Sahoo , Pankaj Kumar
This study presents integrated paleoseismic and geodetic studies from the Kaladungi Fault (KF) in the Kumaon-Garhwal Himalaya to constrain the rupture history of major historical earthquakes. A paleoseismic trench excavated at the base of a 15 m high fault scarp at Nandpur revealed geological evidence of four surface-rupturing paleoearthquakes. In total 24 Optically Stimulated Luminescence (OSL) and 24 radiocarbon (14C) ages allowed robust bracketing of these events.
Based on offsets of sedimentary units and ages we infer that Event-I took place between BCE 2945-1990 and BCE 1480-862, and Event-II was between BCE 1264-643 and BCE 793-287. These events could not be correlated with any paleo-earthquakes due to broad age brackets and nonavailability of any pre-historic records. Event-III occurred between CE 1242–1408 and CE 1415–1529, while Event-IV (MRE) was between CE 1692–1761 and CE 1689–1822. To constrain and correlate the rupture lengths of Event III and Event IV, we considered historical records and regional paleoseismic data from Nepal, Kumaon-Garhwal to the western Himalaya. The Event-III corresponds to the CE 1505 earthquake and Event-IV (MRE) represents the CE 1803 earthquake. Moreover, the long-term slip-rate for the KF is estimated to be ∼7.1 mm/yr, which suggests the ∼40 % of the total slip (∼17.7 mm/yr, estimated from geodetic) being partitioned on this fault.
Paleoseismic evidence for the CE 1803 event indicates surface rupture, as demonstrated by fault displacements and tightly bracketed ages, countering previous claims of a blind rupture. Supporting this interpretation, geodetic modeling and seismicity patterns constrain the downdip locking extent of the Main Himalayan Thrust to ∼100 km north of the Main Frontal Thrust. The reassessment of rupture dimensions for CE 1803 event aligns with a seismic moment magnitude Mw ∼8.1–8.2 rupture.
With updated strain budget of ∼3.9 m of elastic strain accumulated since 1803, the region now represents a mature seismic gap with potential for another great earthquake. This study underscores the importance of integrating trench-based paleoseismic chronologies with GPS-constrained crustal deformation models to enhance seismic hazard assessments along the Himalayan front.
{"title":"Surface rupture signatures of historical earthquakes (16th and 19th centuries) from Kumaon-Garhwal, central Himalaya: Implications for seismic hazard assessment","authors":"Javed N. Malik , Mitthu Dhali , Mahendrasinh S. Gadhavi , Prabhat Kumar , Eshaan Srivastava , Mohd Azhar Ansari , Nayan Sharma , Santiswarup Sahoo , Pankaj Kumar","doi":"10.1016/j.jsg.2025.105567","DOIUrl":"10.1016/j.jsg.2025.105567","url":null,"abstract":"<div><div>This study presents integrated paleoseismic and geodetic studies from the Kaladungi Fault (KF) in the Kumaon-Garhwal Himalaya to constrain the rupture history of major historical earthquakes. A paleoseismic trench excavated at the base of a 15 m high fault scarp at Nandpur revealed geological evidence of four surface-rupturing paleoearthquakes. In total 24 Optically Stimulated Luminescence (OSL) and 24 radiocarbon (14C) ages allowed robust bracketing of these events.</div><div>Based on offsets of sedimentary units and ages we infer that <strong>Event-I</strong> took place between BCE 2945-1990 and BCE 1480-862, and <strong>Event-II</strong> was between BCE 1264-643 and BCE 793-287. These events could not be correlated with any paleo-earthquakes due to broad age brackets and nonavailability of any pre-historic records. <strong>Event-III</strong> occurred between CE 1242–1408 and CE 1415–1529, while <strong>Event-IV</strong> (MRE) was between CE 1692–1761 and CE 1689–1822. To constrain and correlate the rupture lengths of Event III and Event IV, we considered historical records and regional paleoseismic data from Nepal, Kumaon-Garhwal to the western Himalaya. The Event-III corresponds to the CE 1505 earthquake and Event-IV (MRE) represents the CE 1803 earthquake. Moreover, the long-term slip-rate for the KF is estimated to be ∼7.1 mm/yr, which suggests the ∼40 % of the total slip (∼17.7 mm/yr, estimated from geodetic) being partitioned on this fault.</div><div>Paleoseismic evidence for the CE 1803 event indicates surface rupture, as demonstrated by fault displacements and tightly bracketed ages, countering previous claims of a blind rupture. Supporting this interpretation, geodetic modeling and seismicity patterns constrain the downdip locking extent of the Main Himalayan Thrust to ∼100 km north of the Main Frontal Thrust. The reassessment of rupture dimensions for CE 1803 event aligns with a seismic moment magnitude Mw ∼8.1–8.2 rupture.</div><div>With updated strain budget of ∼3.9 m of elastic strain accumulated since 1803, the region now represents a mature seismic gap with potential for another great earthquake. This study underscores the importance of integrating trench-based paleoseismic chronologies with GPS-constrained crustal deformation models to enhance seismic hazard assessments along the Himalayan front.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105567"},"PeriodicalIF":2.9,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145528924","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 : 2025-11-05DOI: 10.1016/j.jsg.2025.105569
Abhisek Basa , Behzad Alaei , Anita Torabi
Generation of 3D fault network in conventional seismic interpretation involves creation of structural models by manually tracking the same discontinuity across seismic horizons on several adjacent vertical profiles. This process is often time-consuming, susceptible to human bias and introduces uncertainties in the characterization of fault geometric attributes - such as length, width and throw - that cannot be reliably quantified. In this study, we adopt a data-driven approach and extract the geometric attributes of the individual segments constituting the 3D seismic fault zone architecture in remarkable detail, that provides insights beyond the capabilities of conventional seismic attributes. This is achieved through the application of 3D Deep Learning (DL) Networks trained on 3D synthetic seismic datasets on a seismic survey from the eastern flank of Polhem Subplatform, SW of Norwegian Barents Sea to automatically create probabilistic fault volumes. Detailed extraction of individual fault segments from the fault probability volume allows us to investigate the seismic fault zone architecture at multiple scales. Our results show that the maximum segment length of all the studied faults is present near the upper tips and reduces towards the lower tips. The fault zone widths of individual segments measured on E-W-oriented vertical scanplanes orthogonal to the strike of the dominant fault set mostly vary between 10 and 20m. They exhibit higher values at locations where fault segments link laterally/vertically or interact with antithetic fault sets with similar strike of the dominant westward dipping fault set. Throw estimates and the total accumulated fault zone widths are higher towards the lower tips of the faults. Thus, the application of Deep Learning enables data-driven, high-resolution visualization of the seismic fault zone architecture and facilitates comprehensive extraction of fault geometric attributes, providing a more robust complement to traditional interpretation techniques.
{"title":"Detailed 3D characterization of fault geometric attributes: Insights from deep learning-based fault imaging in seismic data","authors":"Abhisek Basa , Behzad Alaei , Anita Torabi","doi":"10.1016/j.jsg.2025.105569","DOIUrl":"10.1016/j.jsg.2025.105569","url":null,"abstract":"<div><div>Generation of 3D fault network in conventional seismic interpretation involves creation of structural models by manually tracking the same discontinuity across seismic horizons on several adjacent vertical profiles. This process is often time-consuming, susceptible to human bias and introduces uncertainties in the characterization of fault geometric attributes - such as length, width and throw - that cannot be reliably quantified. In this study, we adopt a data-driven approach and extract the geometric attributes of the individual segments constituting the 3D seismic fault zone architecture in remarkable detail, that provides insights beyond the capabilities of conventional seismic attributes. This is achieved through the application of 3D Deep Learning (DL) Networks trained on 3D synthetic seismic datasets on a seismic survey from the eastern flank of Polhem Subplatform, SW of Norwegian Barents Sea to automatically create probabilistic fault volumes. Detailed extraction of individual fault segments from the fault probability volume allows us to investigate the seismic fault zone architecture at multiple scales. Our results show that the maximum segment length of all the studied faults is present near the upper tips and reduces towards the lower tips. The fault zone widths of individual segments measured on E-W-oriented vertical scanplanes orthogonal to the strike of the dominant fault set mostly vary between 10 and 20m. They exhibit higher values at locations where fault segments link laterally/vertically or interact with antithetic fault sets with similar strike of the dominant westward dipping fault set. Throw estimates and the total accumulated fault zone widths are higher towards the lower tips of the faults. Thus, the application of Deep Learning enables data-driven, high-resolution visualization of the seismic fault zone architecture and facilitates comprehensive extraction of fault geometric attributes, providing a more robust complement to traditional interpretation techniques.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"203 ","pages":"Article 105569"},"PeriodicalIF":2.9,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145532424","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 : 2025-11-05DOI: 10.1016/j.jsg.2025.105571
T.G. Blenkinsop
Stresses in plate interiors vary in magnitude and orientations on various scales, implying that shear and normal stresses on faults may vary regionally. The effects of intraplate regional stress variations are analysed using a recent compilation of in-situ stress to calculate slip and dilation tendencies of United Kingdom onshore faults. The tendencies are normalised to maximum possible values. Stress in UK can be characterised by a strike slip stress field with variable orientations of maximum horizontal stress, SH. Throughout southern UK, SH is orientated NW, giving rise to very low slip and dilation tendencies on NE striking Caledonian faults. North and E to ESE striking faults have very high slip tendencies, and intermediate dilation tendencies. At a major boundary in stress orientation (the Highland Boundary Fault in Scotland), SH changes abruptly to a northerly trend. Steeply dipping Caledonian faults in northern UK such as the Great Glen Fault have very high slip tendencies and intermediate dilation tendencies. Faults with low dips (e.g. the Moine Thrust) have intermediate slip and dilation tendencies. The dramatic change in slip tendencies on steeply dipping Caledonian faults from southern to northern UK illustrates some of the profound consequences of regional scale stress variations. These conclusions are robust to reasonable uncertainties, but the coarse results of this study indicate that more detailed knowledge of stress and fault geometry is necessary for applications such as pump-storage schemes, nuclear power plants, radioactive waste disposal, mining, and carbon sequestration, as well as for seismic hazard analysis.
{"title":"How variations in intraplate stresses affect slip and dilation tendencies of faults: The onshore United Kingdom example","authors":"T.G. Blenkinsop","doi":"10.1016/j.jsg.2025.105571","DOIUrl":"10.1016/j.jsg.2025.105571","url":null,"abstract":"<div><div>Stresses in plate interiors vary in magnitude and orientations on various scales, implying that shear and normal stresses on faults may vary regionally. The effects of intraplate regional stress variations are analysed using a recent compilation of in-situ stress to calculate slip and dilation tendencies of United Kingdom onshore faults. The tendencies are normalised to maximum possible values. Stress in UK can be characterised by a strike slip stress field with variable orientations of maximum horizontal stress, S<sub>H</sub>. Throughout southern UK, S<sub>H</sub> is orientated NW, giving rise to very low slip and dilation tendencies on NE striking Caledonian faults. North and E to ESE striking faults have very high slip tendencies, and intermediate dilation tendencies. At a major boundary in stress orientation (the Highland Boundary Fault in Scotland), S<sub>H</sub> changes abruptly to a northerly trend. Steeply dipping Caledonian faults in northern UK such as the Great Glen Fault have very high slip tendencies and intermediate dilation tendencies. Faults with low dips (e.g. the Moine Thrust) have intermediate slip and dilation tendencies. The dramatic change in slip tendencies on steeply dipping Caledonian faults from southern to northern UK illustrates some of the profound consequences of regional scale stress variations. These conclusions are robust to reasonable uncertainties, but the coarse results of this study indicate that more detailed knowledge of stress and fault geometry is necessary for applications such as pump-storage schemes, nuclear power plants, radioactive waste disposal, mining, and carbon sequestration, as well as for seismic hazard analysis.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"202 ","pages":"Article 105571"},"PeriodicalIF":2.9,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145528926","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":"2025-11-04","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 : 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":"2025-10-29","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}
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