Ian Pierce, Ibrahim Guliyev, Gurban Yetirmishli, Rauf Muradov, Sabina Kazimova, Rashid Javanshir, Gregory P. De Pascale, Ben Johnson, Neill Marshall, Richard Walker, Paul Wordsworth
Here we present the results of the first paleoseismic study of the Kura fold-thrust belt in Azerbaijan based on field mapping, fault trenching, and Quaternary dating. Convergence at rates of ∼10 mm/yr between the Arabian and Eurasian Plates is largely accommodated by the Kura fold-thrust belt which stretches between central Azerbaijan and Georgia along the southern front of the Greater Caucasus (45–48°E). Although destructive historic earthquakes are known here, little is known about the active faults responsible for these earthquakes. A paleoseismic trench was excavated across a 2-m-high fault scarp near Agsu revealing evidence of two surface rupturing earthquakes. Radiocarbon dating of the faulted sediments limits the earthquake timing to AD 1713–1895 and AD 1872–2003. Allowing for uncertainties in dating, the two events likely correspond to historical destructive M ∼ 7 earthquakes near Shamakhi, Azerbaijan in AD 1668 and 1902. A second trench 60 km west of Agsu was excavated near Goychay also revealing evidence of at least one event that occurred 334–118 BC. Holocene shortening and dip-slip rates for the Kura fold-thrust belt are ∼8.0 and 8.5 mm/yr, respectively, based on an uplifted strath terrace west of Agsu. The only known historical devastating (M > ∼7) earthquakes in the Kura region, west of Shamakhi, occurred in 1139 and possibly 1668. The lack of reported historical ruptures from the past 4–8 centuries in the Kura, in contrast with the numerous recorded destructive earthquakes in Shamakhi, suggests that the Kura fold-thrust belt may have accumulated sufficient strain to produce a M > 7.7 earthquake.
{"title":"Surface Rupturing Earthquakes of the Greater Caucasus Frontal Thrusts, Azerbaijan","authors":"Ian Pierce, Ibrahim Guliyev, Gurban Yetirmishli, Rauf Muradov, Sabina Kazimova, Rashid Javanshir, Gregory P. De Pascale, Ben Johnson, Neill Marshall, Richard Walker, Paul Wordsworth","doi":"10.1029/2023tc007758","DOIUrl":"https://doi.org/10.1029/2023tc007758","url":null,"abstract":"Here we present the results of the first paleoseismic study of the Kura fold-thrust belt in Azerbaijan based on field mapping, fault trenching, and Quaternary dating. Convergence at rates of ∼10 mm/yr between the Arabian and Eurasian Plates is largely accommodated by the Kura fold-thrust belt which stretches between central Azerbaijan and Georgia along the southern front of the Greater Caucasus (45–48°E). Although destructive historic earthquakes are known here, little is known about the active faults responsible for these earthquakes. A paleoseismic trench was excavated across a 2-m-high fault scarp near Agsu revealing evidence of two surface rupturing earthquakes. Radiocarbon dating of the faulted sediments limits the earthquake timing to AD 1713–1895 and AD 1872–2003. Allowing for uncertainties in dating, the two events likely correspond to historical destructive <i>M</i> ∼ 7 earthquakes near Shamakhi, Azerbaijan in AD 1668 and 1902. A second trench 60 km west of Agsu was excavated near Goychay also revealing evidence of at least one event that occurred 334–118 BC. Holocene shortening and dip-slip rates for the Kura fold-thrust belt are ∼8.0 and 8.5 mm/yr, respectively, based on an uplifted strath terrace west of Agsu. The only known historical devastating (<i>M</i> > ∼7) earthquakes in the Kura region, west of Shamakhi, occurred in 1139 and possibly 1668. The lack of reported historical ruptures from the past 4–8 centuries in the Kura, in contrast with the numerous recorded destructive earthquakes in Shamakhi, suggests that the Kura fold-thrust belt may have accumulated sufficient strain to produce a <i>M</i> > 7.7 earthquake.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"79 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140097472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yu Tang, Xiao Liang, Genhou Wang, Dian Li, Zhanhui Qing, Yipeng Feng, Wei Zhang, Ning Han, Yang Tian, Zhuosheng Wang
The poor understanding of the structural history of the Late Triassic flysch in the northeastern Tethyan Himalaya has caused many disputes regarding India-Asia collisional tectonics. Here, we conducted an integrated study including tectonostratigraphic analysis, structural analysis, and zircon U‒Pb and muscovite 40Ar/39Ar dating to unravel the structural evolution of the Late Triassic flysch. Field geological mapping revealed that the flysch can be subdivided into three structural units, including the Gyaca mélange, Qiongjie-Dengmu shear zone and Langjiexue fold-thrust belt. The three units all contain voluminous siliciclastic rocks deposited in an abyssal submarine fan environment at the Indian passive continental margin. The Gyaca mélange shows a two-stage deformation process that generated a collisional mélange resulting from the subduction of the Indian passive continental margin. 40Ar/39Ar dating of top-to-the-south shear bands and block-in-matrix structure indicate that the India-Asia collision happened no later than the Selandian (ca. 60 Ma). The divergent imbricated thrusting and folding of the Gyaca mélange and Langjiexue fold-thrust belt formed a positive flower structure. The zircon U‒Pb and 40Ar/39Ar dating of syntectonic dikes and sericite flakes within the Gyaca mélange yield ages of ca. 56–55 Ma for the genesis of the divergent structures. Moreover, the Qiongjie-Dengmu dextral shear zone yields a sericite 40Ar/39Ar age of ca. 35 Ma and thus indicates a transient strike-slip stress regime. Generally, the early India-Asia collision tectonics in the northeastern Tethyan Himalaya showed episodic evolution with changing structural styles from mélange formation to imbricate fold-thrust belt development and finally strike-slip shear generation.
{"title":"Diverse Structural Styles of the Northeastern Tethyan Himalaya in Southern Tibet Reveal the Early Collisional Tectonics of India and Asia","authors":"Yu Tang, Xiao Liang, Genhou Wang, Dian Li, Zhanhui Qing, Yipeng Feng, Wei Zhang, Ning Han, Yang Tian, Zhuosheng Wang","doi":"10.1029/2023tc007954","DOIUrl":"https://doi.org/10.1029/2023tc007954","url":null,"abstract":"The poor understanding of the structural history of the Late Triassic flysch in the northeastern Tethyan Himalaya has caused many disputes regarding India-Asia collisional tectonics. Here, we conducted an integrated study including tectonostratigraphic analysis, structural analysis, and zircon U‒Pb and muscovite <sup>40</sup>Ar/<sup>39</sup>Ar dating to unravel the structural evolution of the Late Triassic flysch. Field geological mapping revealed that the flysch can be subdivided into three structural units, including the Gyaca mélange, Qiongjie-Dengmu shear zone and Langjiexue fold-thrust belt. The three units all contain voluminous siliciclastic rocks deposited in an abyssal submarine fan environment at the Indian passive continental margin. The Gyaca mélange shows a two-stage deformation process that generated a collisional mélange resulting from the subduction of the Indian passive continental margin. <sup>40</sup>Ar/<sup>39</sup>Ar dating of top-to-the-south shear bands and block-in-matrix structure indicate that the India-Asia collision happened no later than the Selandian (ca. 60 Ma). The divergent imbricated thrusting and folding of the Gyaca mélange and Langjiexue fold-thrust belt formed a positive flower structure. The zircon U‒Pb and <sup>40</sup>Ar/<sup>39</sup>Ar dating of syntectonic dikes and sericite flakes within the Gyaca mélange yield ages of ca. 56–55 Ma for the genesis of the divergent structures. Moreover, the Qiongjie-Dengmu dextral shear zone yields a sericite <sup>40</sup>Ar/<sup>39</sup>Ar age of ca. 35 Ma and thus indicates a transient strike-slip stress regime. Generally, the early India-Asia collision tectonics in the northeastern Tethyan Himalaya showed episodic evolution with changing structural styles from mélange formation to imbricate fold-thrust belt development and finally strike-slip shear generation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"56 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140071957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Villani, A. Antonioli, M. Pastori, P. Baccheschi, M. G. Ciaccio
In the Eastern Alps, the indentation of the Adriatic promontory since the Cenozoic affected the kinematics of separate crustal domains bounded by faults that accommodate lateral extrusion processes and differential shortening. Deciphering the pattern of crustal stresses in the orogen interior is challenging, due to the lack of in situ stress measurements at crustal depths. We define stress regimes and the orientations of the most-compressive horizontal stress (SHmax) by integrating published results with new data, including stress analysis from fault plane solutions, estimation of crustal anisotropy through the shear wave splitting analysis, paleostress determination from fault slip data, and computation of cumulative seismic displacements. The retrieved regional SHmax are generally consistent with N-S convergence. In the northern part of the study area, current stress orientations are almost parallel to paleo-SHmax, suggesting a rather uniform compressional regime since the late Cenozoic. Conversely, sharp deflections and divergence with paleo-SHmax appear at the western border of the Adriatic promontory across major transpressive and extensional shear zones and in the Southalpine domain, indicating a change in tectonically induced second-order stresses. A current strike-slip regime with subordinate orogen-parallel seismic displacements affects a belt to north of the Periadriatic Lineament and NE-extension characterizes the Ortles-Engandine region. Seismic anisotropy locally exhibits fault-parallel fast axes (Brenner-Giudicarie fault-systems, Dinaric and Southalpine thrusts), whereas stress-induced anisotropy parallel to SHmax characterizes the southern part of the orogen. Cumulative seismic displacements are small compared to geodetic ones, and unravel partitioning of deformation into second-order transpressive and extensional belts in response to indentation.
{"title":"Stress Patterns and Crustal Anisotropy in the Eastern Alps: Insights From Seismological and Geological Observations","authors":"F. Villani, A. Antonioli, M. Pastori, P. Baccheschi, M. G. Ciaccio","doi":"10.1029/2023tc008033","DOIUrl":"https://doi.org/10.1029/2023tc008033","url":null,"abstract":"In the Eastern Alps, the indentation of the Adriatic promontory since the Cenozoic affected the kinematics of separate crustal domains bounded by faults that accommodate lateral extrusion processes and differential shortening. Deciphering the pattern of crustal stresses in the orogen interior is challenging, due to the lack of in situ stress measurements at crustal depths. We define stress regimes and the orientations of the most-compressive horizontal stress (S<sub>Hmax</sub>) by integrating published results with new data, including stress analysis from fault plane solutions, estimation of crustal anisotropy through the shear wave splitting analysis, paleostress determination from fault slip data, and computation of cumulative seismic displacements. The retrieved regional S<sub>Hmax</sub> are generally consistent with N-S convergence. In the northern part of the study area, current stress orientations are almost parallel to paleo-S<sub>Hmax</sub>, suggesting a rather uniform compressional regime since the late Cenozoic. Conversely, sharp deflections and divergence with paleo-S<sub>Hmax</sub> appear at the western border of the Adriatic promontory across major transpressive and extensional shear zones and in the Southalpine domain, indicating a change in tectonically induced second-order stresses. A current strike-slip regime with subordinate orogen-parallel seismic displacements affects a belt to north of the Periadriatic Lineament and NE-extension characterizes the Ortles-Engandine region. Seismic anisotropy locally exhibits fault-parallel fast axes (Brenner-Giudicarie fault-systems, Dinaric and Southalpine thrusts), whereas stress-induced anisotropy parallel to S<sub>Hmax</sub> characterizes the southern part of the orogen. Cumulative seismic displacements are small compared to geodetic ones, and unravel partitioning of deformation into second-order transpressive and extensional belts in response to indentation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"27 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140056451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Filip Tomek, Jiří Žák, Kryštof Verner, Josef Ježek, Scott R. Paterson
The relation of plate kinematics to the structural record of arc plutons and their host rocks is complex and still not fully understood. We address this issue through a combination of field mapping, structural analysis, anisotropy of magnetic susceptibility analysis, and fabric modeling in the Late Cretaceous Tuolumne Intrusive Complex, Sierra Nevada, California. A pattern of anti-clockwise rotation from ∼NNW–SSE to WNW–ESE steep foliations and change in fabric ellipsoid shape from oblate to prolate was revealed in successively emplaced Kuna Crest (∼95–92 Ma), Half Dome (∼92–89 Ma), and Cathedral Peak (∼89–84 Ma) granodiorites. The numerical model indicates that the Kuna Crest was emplaced in a transpressional setting with an angle of convergence α = 60–40°, whereas the Half Dome and Cathedral Peak required simultaneous vertical constriction overprinted by transpression with α = 35–15°. This transition, which occurred at ∼92 Ma, is accompanied by a shallowing of the lineation plunge observed also in other ∼88–84 Ma central Sierra Nevada plutons. Provided that the Cretaceous Sierra Nevada arc was constructed during overall dextral transpression, these transitions reflect significant changes in kinematics, where ∼107–92 Ma plutons were emplaced during pure shear-dominated transpression, which was followed by a transition to wrench-dominated transpression recorded in ∼92–84 Ma plutons. Such a transition in kinematics is explained as a result of progressively increasing obliquity of the relative convergence of the Farallon plate subducting beneath the North American continental margin, in agreement with most paleogeographic reconstructions.
板块运动学与弧形柱岩及其母岩的结构记录之间的关系非常复杂，至今仍未完全搞清楚。我们在加利福尼亚州内华达山脉的晚白垩世图奥卢姆内侵入复合体（Tuolumne Intrusive Complex）中，通过实地测绘、结构分析、磁感应强度各向异性分析和构造建模相结合的方法来解决这个问题。在相继出露的 Kuna Crest（95-92 Ma）、Half Dome（92-89 Ma）和 Cathedral Peak（89-84 Ma）花岗闪长岩中，发现了从∼NNW-SSE 到 WNW-ESE 陡峭褶皱的逆时针旋转模式，以及构造椭球体形状从扁球形到长球形的变化。数值模型表明，库纳峰丛是在换位环境中堆积的，其汇聚角α=60-40°，而半圆顶和大教堂峰丛则需要同时进行垂直收缩，并叠加换位作用，其汇聚角α=35-15°。这一转变发生在 ∼92 Ma，与此同时，在其他 ∼88-84 Ma 的内华达山脉中部岩浆岩中也观察到了线状暴跌的变浅。如果白垩纪内华达山脉弧是在整体右旋转位过程中形成的，那么这些转变反映了运动学的重大变化，即 107-92 Ma ∼的岩柱是在纯剪切主导的转位过程中喷出的，而在 92-84 Ma ∼的岩柱中则过渡到了扳动主导的转位。这种运动学上的过渡可解释为俯冲于北美大陆边缘之下的法拉隆板块相对辐合的斜度逐渐增大的结果，这与大多数古地理重建一致。
{"title":"A Complex Interplay Between Pluton Emplacement, Tectonic Deformation, and Plate Kinematics in the Cretaceous Sierra Nevada Magmatic Arc, California","authors":"Filip Tomek, Jiří Žák, Kryštof Verner, Josef Ježek, Scott R. Paterson","doi":"10.1029/2023tc007822","DOIUrl":"https://doi.org/10.1029/2023tc007822","url":null,"abstract":"The relation of plate kinematics to the structural record of arc plutons and their host rocks is complex and still not fully understood. We address this issue through a combination of field mapping, structural analysis, anisotropy of magnetic susceptibility analysis, and fabric modeling in the Late Cretaceous Tuolumne Intrusive Complex, Sierra Nevada, California. A pattern of anti-clockwise rotation from ∼NNW–SSE to WNW–ESE steep foliations and change in fabric ellipsoid shape from oblate to prolate was revealed in successively emplaced Kuna Crest (∼95–92 Ma), Half Dome (∼92–89 Ma), and Cathedral Peak (∼89–84 Ma) granodiorites. The numerical model indicates that the Kuna Crest was emplaced in a transpressional setting with an angle of convergence <i>α</i> = 60–40°, whereas the Half Dome and Cathedral Peak required simultaneous vertical constriction overprinted by transpression with <i>α</i> = 35–15°. This transition, which occurred at ∼92 Ma, is accompanied by a shallowing of the lineation plunge observed also in other ∼88–84 Ma central Sierra Nevada plutons. Provided that the Cretaceous Sierra Nevada arc was constructed during overall dextral transpression, these transitions reflect significant changes in kinematics, where ∼107–92 Ma plutons were emplaced during pure shear-dominated transpression, which was followed by a transition to wrench-dominated transpression recorded in ∼92–84 Ma plutons. Such a transition in kinematics is explained as a result of progressively increasing obliquity of the relative convergence of the Farallon plate subducting beneath the North American continental margin, in agreement with most paleogeographic reconstructions.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"2014 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140056334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiuxi Wang, Massimiliano Zattin, Yu Yang, Jia Tao, Huiming Liu, Yanbo Zhang, Hong Wang, Bozhong Pang, Linbing Wang, Minxiao Ji
The Cenozoic growth history of the northeast (NE) Tibetan Plateau has been strongly debated in the past few years with three deformation models being proposed: progressive northeastward propagation, out-of-sequence deformation, and episodic deformation. Reconstruction of the long-term deformation and exhumation history of the different blocks can help elucidate the growth pattern and tectonic processes involved in the formation of the Plateau. Both the Qaidam and Jiuquan basins—the two largest basins of the NE Tibetan Plateau—contain continuous and well-exposed successions of synorogenic sediments that span the entire Cenozoic. We used apatite fission-track thermochronology, sedimentary facies, and structural and provenance analyses of these successions to determine the exhumation history of the Tibetan Plateau. Five distinct fast exhumation events were recognized and dated: 65–54, 43–39, 34–29, 24–21, and 16–15 Ma. Comparison with existing morphotectonic information enabled us to reconstruct a multiple-stage growth scenario for the NE Tibetan Plateau in the context of the surface uplift phases across the Himalayan-Tibetan orogen during the Cenozoic. Overall, our findings support the episodic deformation model and emphasizes that the current relief of the NE Tibetan Plateau is largely derived from these five of stage of exhumation.
{"title":"Multiple Exhumation Stages During the Cenozoic Evolution of the Northeast Tibetan Plateau","authors":"Xiuxi Wang, Massimiliano Zattin, Yu Yang, Jia Tao, Huiming Liu, Yanbo Zhang, Hong Wang, Bozhong Pang, Linbing Wang, Minxiao Ji","doi":"10.1029/2023tc007850","DOIUrl":"https://doi.org/10.1029/2023tc007850","url":null,"abstract":"The Cenozoic growth history of the northeast (NE) Tibetan Plateau has been strongly debated in the past few years with three deformation models being proposed: progressive northeastward propagation, out-of-sequence deformation, and episodic deformation. Reconstruction of the long-term deformation and exhumation history of the different blocks can help elucidate the growth pattern and tectonic processes involved in the formation of the Plateau. Both the Qaidam and Jiuquan basins—the two largest basins of the NE Tibetan Plateau—contain continuous and well-exposed successions of synorogenic sediments that span the entire Cenozoic. We used apatite fission-track thermochronology, sedimentary facies, and structural and provenance analyses of these successions to determine the exhumation history of the Tibetan Plateau. Five distinct fast exhumation events were recognized and dated: 65–54, 43–39, 34–29, 24–21, and 16–15 Ma. Comparison with existing morphotectonic information enabled us to reconstruct a multiple-stage growth scenario for the NE Tibetan Plateau in the context of the surface uplift phases across the Himalayan-Tibetan orogen during the Cenozoic. Overall, our findings support the episodic deformation model and emphasizes that the current relief of the NE Tibetan Plateau is largely derived from these five of stage of exhumation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"1 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140056436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. M. Tewksbury-Christle, W. M. Behr, M. A. Helper, D. F. Stockli
The Klamath Mountains in northern California and southern Oregon are thought to record 200+ m.y. of subduction and terrane accretion, whereas the outboard Franciscan Complex records ocean-continent subduction along the North American margin. Unraveling the Klamath Mountains' Late Jurassic history could help constrain this transition in subduction style. Key is the Mesozoic Condrey Mountain Schist (CMS), comprising, in part, a subduction complex that occupies a structural window through older, overlying central Klamath thrust sheets but with otherwise uncertain relationships to more outboard Klamath or Franciscan terranes. The CMS consists of two units (upper and lower), which could be correlated with (a) other Klamath terranes, (b) the Franciscan, or (c) neither based on regional structures and limited extant age data. Upper CMS protolith and metamorphic dates overlap with other Klamath terranes, but the lower CMS remains enigmatic. We used multiple geochronometers to constrain the timing of lower CMS deposition and metamorphism. Maximum depositional ages (MDAs) derived from detrital zircon geochronology of metasedimentary rocks are 153–135 Ma. Metamorphic ages from white mica K-Ar and Rb-Sr multi-mineral isochrons from intercalated and coherently deformed metamafic lenses are 133–116 Ma. Lower CMS MDAs (<153 Ma) predominantly postdate other Klamath terrane ages, but subduction metamorphism appears to start before the earliest coherent Franciscan underplating (ca. 123 Ma). The lower CMS thus occupies a spatial and temporal position between the Klamath Mountains and Franciscan and preserves a non-retrogressed record of the Franciscan Complex's early history (>123 Ma), otherwise only partially preserved in retrogressed Franciscan high grade blocks.
{"title":"Tectonic Evolution of the Condrey Mountain Schist: An Intact Record of Late Jurassic to Early Cretaceous Franciscan Subduction and Underplating","authors":"C. M. Tewksbury-Christle, W. M. Behr, M. A. Helper, D. F. Stockli","doi":"10.1029/2023tc008115","DOIUrl":"https://doi.org/10.1029/2023tc008115","url":null,"abstract":"The Klamath Mountains in northern California and southern Oregon are thought to record 200+ m.y. of subduction and terrane accretion, whereas the outboard Franciscan Complex records ocean-continent subduction along the North American margin. Unraveling the Klamath Mountains' Late Jurassic history could help constrain this transition in subduction style. Key is the Mesozoic Condrey Mountain Schist (CMS), comprising, in part, a subduction complex that occupies a structural window through older, overlying central Klamath thrust sheets but with otherwise uncertain relationships to more outboard Klamath or Franciscan terranes. The CMS consists of two units (upper and lower), which could be correlated with (a) other Klamath terranes, (b) the Franciscan, or (c) neither based on regional structures and limited extant age data. Upper CMS protolith and metamorphic dates overlap with other Klamath terranes, but the lower CMS remains enigmatic. We used multiple geochronometers to constrain the timing of lower CMS deposition and metamorphism. Maximum depositional ages (MDAs) derived from detrital zircon geochronology of metasedimentary rocks are 153–135 Ma. Metamorphic ages from white mica K-Ar and Rb-Sr multi-mineral isochrons from intercalated and coherently deformed metamafic lenses are 133–116 Ma. Lower CMS MDAs (<153 Ma) predominantly postdate other Klamath terrane ages, but subduction metamorphism appears to start before the earliest coherent Franciscan underplating (ca. 123 Ma). The lower CMS thus occupies a spatial and temporal position between the Klamath Mountains and Franciscan and preserves a non-retrogressed record of the Franciscan Complex's early history (>123 Ma), otherwise only partially preserved in retrogressed Franciscan high grade blocks.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"107 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140044810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Manuel Curzi, Giulio Viola, Costantino Zuccari, Luca Aldega, Andrea Billi, Roelant van der Lelij, Andrew Kylander-Clark, Gianluca Vignaroli
The Eastern Southern Alps fold-and-thrust belt (ESA) is part of the seismically active S-verging retro-wedge of the European Alps. Its temporal tectonic evolution during continental shortening has so far been constrained by few and low-resolution indirect time constraints. Aiming at better elucidating the ESA spatiotemporal evolution, we gathered new structural and geochronological data from two regional thrust systems: the innermost south verging Valsugana Thrust (VT) and the more external Belluno Thrust System (BTS). Field work allowed us to constrain the geometry and kinematics of those thrusts and related folds and informed our sampling strategy to carry out fault gouge K-Ar and tectonic carbonate U-Pb dating from representative samples structurally associated with the VT and BTS. Our results suggest that the VT was active already in the Late Cretaceous (between ∼78 and 76 Ma) in response to far-field stresses, with repeated reactivation continuing to the Late Miocene (∼6 Ma). The BTS recorded two distinct deformation events during the Oligocene (∼30 Ma) and at the Oligocene-Miocene boundary (∼23 Ma). The VT was active for ∼72 Myr and partly acted during out-of-sequence thrusting. Based on regional correlations, we propose that the ESA share a similar spatiotemporal deformation history with the central Southern Alps farther to the west. We suggest a conceptual regional tectonic model wherein multiple, broadly coeval deformation events occurred in the entire Southern Alps during their long-lived orogenic deformation in response to generally continuous NW-SE shortening.
南阿尔卑斯山东部褶皱-推覆带（ESA）是欧洲阿尔卑斯山地震活跃的 S 向后缘的一部分。迄今为止，其在大陆缩短过程中的时间构造演化一直受到很少且分辨率较低的间接时间约束。为了更好地阐明欧空局的时空演化，我们从两个区域推力系统收集了新的构造和地质年代数据：最内侧的南向瓦卢加纳推力系统（VT）和更外侧的贝鲁诺推力系统（BTS）。野外工作使我们能够确定这些推力和相关褶皱的几何和运动学特征，并为我们从与 VT 和 BTS 结构相关的代表性样本中进行断层冲沟 K-Ar 和构造碳酸盐 U-Pb 测年的取样策略提供了依据。我们的研究结果表明，VT 在晚白垩世（78 ∼ 76 Ma 之间）就已经因远场应力而开始活跃，其反复重新活跃一直持续到晚中新世（6 Ma ∼ 6 Ma）。BTS在渐新世（30 Ma）和渐新世-中新世边界（23 Ma）记录了两次不同的变形事件。VT活跃了72 Myr，部分作用于序外推力。根据区域相关性，我们提出欧空局与更西边的南阿尔卑斯山中部有着相似的时空变形历史。我们提出了一个概念性的区域构造模型，即在整个南阿尔卑斯山漫长的造山运动变形过程中，发生了多次大体共时的变形事件，以应对总体上持续的西北-东南向缩短。
{"title":"Tectonic Evolution of the Eastern Southern Alps (Italy): A Reappraisal From New Structural Data and Geochronological Constraints","authors":"Manuel Curzi, Giulio Viola, Costantino Zuccari, Luca Aldega, Andrea Billi, Roelant van der Lelij, Andrew Kylander-Clark, Gianluca Vignaroli","doi":"10.1029/2023tc008013","DOIUrl":"https://doi.org/10.1029/2023tc008013","url":null,"abstract":"The Eastern Southern Alps fold-and-thrust belt (ESA) is part of the seismically active S-verging retro-wedge of the European Alps. Its temporal tectonic evolution during continental shortening has so far been constrained by few and low-resolution indirect time constraints. Aiming at better elucidating the ESA spatiotemporal evolution, we gathered new structural and geochronological data from two regional thrust systems: the innermost south verging Valsugana Thrust (VT) and the more external Belluno Thrust System (BTS). Field work allowed us to constrain the geometry and kinematics of those thrusts and related folds and informed our sampling strategy to carry out fault gouge K-Ar and tectonic carbonate U-Pb dating from representative samples structurally associated with the VT and BTS. Our results suggest that the VT was active already in the Late Cretaceous (between ∼78 and 76 Ma) in response to far-field stresses, with repeated reactivation continuing to the Late Miocene (∼6 Ma). The BTS recorded two distinct deformation events during the Oligocene (∼30 Ma) and at the Oligocene-Miocene boundary (∼23 Ma). The VT was active for ∼72 Myr and partly acted during out-of-sequence thrusting. Based on regional correlations, we propose that the ESA share a similar spatiotemporal deformation history with the central Southern Alps farther to the west. We suggest a conceptual regional tectonic model wherein multiple, broadly coeval deformation events occurred in the entire Southern Alps during their long-lived orogenic deformation in response to generally continuous NW-SE shortening.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"30 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140044918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chance B. Ronemus, Caden J. Howlett, Peter G. DeCelles, Barbara Carrapa, Sarah W. M. George
The Manantiales basin contains >4 km of nonmarine sedimentary strata that accumulated at 31.75–32.5°S during construction of the High Andes. We report field and analytical data from the underexplored northern portion of this basin. The basin contains upper Eocene–middle Miocene strata that accumulated in back-bulge or distal foredeep through inner-wedge-top depozones of the Andean foreland basin as it migrated through this region. A revised accumulation history for the basin-filling Río de los Patos and Chinches Formations supports a regional pattern of flexure in front of an east-vergent orogenic wedge. The former formation consists of eolian and localized fluviolacustrine deposits which accumulated between ca. 38 Ma and ≤34 Ma during thrust belt development in Chile. A subsequent ≤12 Myr hiatus may reflect passage of the flexural forebulge or cessation of subsidence during orogenic quiescence. The overlying Chinches Formation records a transition from the foredeep to wedge-top depozones. Foredeep deposits of east-flowing, meandering streams were incised prior to ca. 18 Ma, after which deposits of axial rivers, playas, and perennial lakes ponded in a depression behind orogenic topography to the east. After ca. 15 Ma, alluvial-fan deposits were syndepositionally deformed adjacent to growing thrust-belt structures along the western basin margin. Although the basin record supports a westward step in the locus of deformation during Early–Middle Miocene time, it conflicts with models involving west-vergence of the orogenic wedge. Rather, this pattern can be explained as out-of-sequence deformation alternating with wedge forward propagation, consistent with Coulomb wedge models incorporating syntectonic sedimentation.
Manantiales 盆地包含 4 公里长的非海相沉积地层，这些地层在高安第斯山脉形成过程中积聚在 31.75-32.5°S 处。我们报告了该盆地北部未充分勘探地区的实地数据和分析数据。该盆地包含上新世-中新世地层，这些地层在安第斯前陆盆地迁移经过该地区时，通过内侧楔顶剥蚀带在后凸或远端前深部堆积。经修订的充填盆地的里奥德洛斯帕托斯地层和钦奇地层的堆积历史，支持了东向造山楔前的区域褶皱模式。前一个地层由约 38 Ma 至 ≤34 Ma 之间在智利推力带发展过程中堆积的风化沉积物和局部流积物组成。随后≤12 Myr的间断可能反映了挠曲前突的经过或造山运动静止期间的沉降停止。上覆的钦奇地层记录了前深部向楔顶剥蚀带的过渡。在大约18Ma之前，东流蜿蜒溪流的前深部沉积物被切开，之后，轴向河流、泥沼和多年生湖泊的沉积物在造山地形东侧的洼地中汇集。在大约 15 Ma 之后，冲积-扇状地形开始形成。大约 15 Ma 之后，冲积扇沉积物在盆地西部边缘不断增长的推力带构造附近发生了联合沉积变形。尽管盆地记录支持早中新世时期变形位置向西移动，但这与造山楔向西辐合的模式相冲突。相反，这种模式可以解释为序列外变形与楔向前传播交替进行，与包含综合沉积作用的库仑楔模型相一致。
{"title":"The Manantiales Basin, Southern Central Andes (∼32°S), Preserves a Record of Late Eocene–Miocene Episodic Growth of an East-Vergent Orogenic Wedge","authors":"Chance B. Ronemus, Caden J. Howlett, Peter G. DeCelles, Barbara Carrapa, Sarah W. M. George","doi":"10.1029/2023tc008100","DOIUrl":"https://doi.org/10.1029/2023tc008100","url":null,"abstract":"The Manantiales basin contains >4 km of nonmarine sedimentary strata that accumulated at 31.75–32.5°S during construction of the High Andes. We report field and analytical data from the underexplored northern portion of this basin. The basin contains upper Eocene–middle Miocene strata that accumulated in back-bulge or distal foredeep through inner-wedge-top depozones of the Andean foreland basin as it migrated through this region. A revised accumulation history for the basin-filling Río de los Patos and Chinches Formations supports a regional pattern of flexure in front of an east-vergent orogenic wedge. The former formation consists of eolian and localized fluviolacustrine deposits which accumulated between ca. 38 Ma and ≤34 Ma during thrust belt development in Chile. A subsequent ≤12 Myr hiatus may reflect passage of the flexural forebulge or cessation of subsidence during orogenic quiescence. The overlying Chinches Formation records a transition from the foredeep to wedge-top depozones. Foredeep deposits of east-flowing, meandering streams were incised prior to ca. 18 Ma, after which deposits of axial rivers, playas, and perennial lakes ponded in a depression behind orogenic topography to the east. After ca. 15 Ma, alluvial-fan deposits were syndepositionally deformed adjacent to growing thrust-belt structures along the western basin margin. Although the basin record supports a westward step in the locus of deformation during Early–Middle Miocene time, it conflicts with models involving west-vergence of the orogenic wedge. Rather, this pattern can be explained as out-of-sequence deformation alternating with wedge forward propagation, consistent with Coulomb wedge models incorporating syntectonic sedimentation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"22 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140008436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhenyu Peng, Xin Wang, Fabien Graveleau, Bruno C. Vendeville, Alan G. Nunns
In the rejuvenated mountain front, preexisting basement structures are often reactivated and interact with the subsequent thin-skinned deformation. How the deep structures affect the shallower ones is key to establishing the processes and mechanisms for the foreland fold-and-thrust system. We presented an exceptional case study on the structural inheritance between the deep Mesozoic strike-slip faults and the shallow Cenozoic contractional folds from the Northern Tianshan foreland basin, Northwest China, using high-resolution 2-D and 3-D seismic data. Based on the interpretation of seismic data and progressive restoration, our study illustrated the NW-trending Ai-Ka strike-slip faults controlled a dextral shear zone, which initiated the Gaoquan restraining bend in the basement during Jurassic. Later, these strike-slip structures, close to the mountain front, were reactivated during the N-S Mio-Pliocene contraction, and folded the upper décollements that characterized the localization of thin-skinned deformation. In contrast, in the further foreland, nonreactive strike-slip faults controlled basal décollement pinch-out, which localizes the thin-skinned deformation, resulting in en échelon folds that trace the strike of the deep strike-slip faults. The onset time of each anticline shows that the thin-skinned deformation first extended laterally and then propagated further north, resulting in ca. 7 km shortening along the whole foreland. Moreover, the shortening rate decreased eastward from 0.90 to 1.46 mm/yr along the Gaoquan-Kayindike structural line to 0.24–0.37 mm/yr along the Dunan structural line as the Sikeshu depression, constrained by the NW-trending Ai-Ka strike-slip fault, narrowed eastward. This feature implies that the width of the depression may control the amount of displacement propagation.
{"title":"Structural Interactions Between Deep Mesozoic Strike-Slip Faults and Shallow Cenozoic Contractional Folds in the Northern Tianshan Foreland Basin (NW China)","authors":"Zhenyu Peng, Xin Wang, Fabien Graveleau, Bruno C. Vendeville, Alan G. Nunns","doi":"10.1029/2023tc007986","DOIUrl":"https://doi.org/10.1029/2023tc007986","url":null,"abstract":"In the rejuvenated mountain front, preexisting basement structures are often reactivated and interact with the subsequent thin-skinned deformation. How the deep structures affect the shallower ones is key to establishing the processes and mechanisms for the foreland fold-and-thrust system. We presented an exceptional case study on the structural inheritance between the deep Mesozoic strike-slip faults and the shallow Cenozoic contractional folds from the Northern Tianshan foreland basin, Northwest China, using high-resolution 2-D and 3-D seismic data. Based on the interpretation of seismic data and progressive restoration, our study illustrated the NW-trending Ai-Ka strike-slip faults controlled a dextral shear zone, which initiated the Gaoquan restraining bend in the basement during Jurassic. Later, these strike-slip structures, close to the mountain front, were reactivated during the N-S Mio-Pliocene contraction, and folded the upper <i>décollements</i> that characterized the localization of thin-skinned deformation. In contrast, in the further foreland, nonreactive strike-slip faults controlled basal <i>décollement</i> pinch-out, which localizes the thin-skinned deformation, resulting in <i>en échelon</i> folds that trace the strike of the deep strike-slip faults. The onset time of each anticline shows that the thin-skinned deformation first extended laterally and then propagated further north, resulting in ca. 7 km shortening along the whole foreland. Moreover, the shortening rate decreased eastward from 0.90 to 1.46 mm/yr along the Gaoquan-Kayindike structural line to 0.24–0.37 mm/yr along the Dunan structural line as the Sikeshu depression, constrained by the NW-trending Ai-Ka strike-slip fault, narrowed eastward. This feature implies that the width of the depression may control the amount of displacement propagation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"13 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139948356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Asier Madarieta-Txurruka, Lourdes González-Castillo, José A. Peláez, Jesús Galindo-Zaldívar, María J. Borque, María C. Lacy, Antonio M. Ruiz-Armenteros, Jesús Henares, Patricia Ruano, Alberto Sánchez-Alzola, Manuel Avilés, Gracia Rodríguez-Caderot, Francisco José Martínez-Moreno, Víctor Tendero-Salmerón, Raquel Vinardell-Peña, Antonio J. Gil
The central Betic Cordillera, southern Spain, is affected by an uplift related to the NNW–SSE Eurasia-Nubia convergence and shallow ENE–WSW orthogonal extension accommodated by the extensional system of the Granada Basin. The combination of geophysical, geodetic, and geological data reveals that the southwestern boundary of this extensional system is a seismically active compressional front extending from the W to the SW of the Granada Basin. The near-field Global Navigation Satellite System data determine NNE–SSW shortening of up to 2 mm/yr of the compressional front in the Zafarraya Polje. In this setting, the normal Ventas de Zafarraya Fault developed as a result of the bending-moment extension of the Sierra de Alhama antiform and was last reactivated during the 1884 Andalusian earthquake (Mw 6.5). The uplift in the central Betic Cordillera together with the subsidence in the Western Alborán Basin may facilitate a westward to southwestward gravitational collapse through the extensional detachment of the Granada Basin. The heterogeneous crust of the Betic Cordillera would generate the compressional front, which is divided into two sectors: thrusting to the west, and folding associated with buttressing to the south. Our results evidence that basal detachments, linking extensional fault activity with compressional fronts, may determine the activity of local surface structures and the geological hazard in densely populated regions.
西班牙南部的贝蒂科迪勒拉山系中部受到与欧亚-努比亚西北-东南辐合有关的隆起以及格拉纳达盆地延伸系统所容纳的东偏东-西偏西正交浅延伸的影响。地球物理、大地测量和地质数据的综合显示，该延伸系统的西南边界是一个地震活跃的压缩前沿，从格拉纳达盆地的西部延伸到西南部。全球导航卫星系统的近场数据确定，Zafarraya Polje 地区的压缩前线向东北-西南方向缩短，缩短幅度高达 2 毫米/年。在这种情况下，正常的 Ventas de Zafarraya 断层因 Sierra de Alhama antiform 的弯曲延伸而形成，最后一次重新激活是在 1884 年安达卢西亚地震（Mw 6.5）期间。贝蒂科迪勒拉山系中部的隆起和西阿尔博兰盆地的下沉可能会通过格拉纳达盆地的延伸剥离，促进向西至西南的重力塌陷。贝蒂科迪勒拉山系的异质地壳会产生压缩锋，压缩锋分为两部分：向西的推力和向南与对接相关的褶皱。我们的研究结果证明，基底剥离将延伸断层活动与压缩锋联系在一起，可能会决定当地地表结构的活动以及人口稠密地区的地质灾害。
{"title":"Active Shortening Simultaneous to Normal Faulting Based on GNSS, Geophysical, and Geological Data: The Seismogenic Ventas de Zafarraya Fault (Betic Cordillera, Southern Spain)","authors":"Asier Madarieta-Txurruka, Lourdes González-Castillo, José A. Peláez, Jesús Galindo-Zaldívar, María J. Borque, María C. Lacy, Antonio M. Ruiz-Armenteros, Jesús Henares, Patricia Ruano, Alberto Sánchez-Alzola, Manuel Avilés, Gracia Rodríguez-Caderot, Francisco José Martínez-Moreno, Víctor Tendero-Salmerón, Raquel Vinardell-Peña, Antonio J. Gil","doi":"10.1029/2023tc007956","DOIUrl":"https://doi.org/10.1029/2023tc007956","url":null,"abstract":"The central Betic Cordillera, southern Spain, is affected by an uplift related to the NNW–SSE Eurasia-Nubia convergence and shallow ENE–WSW orthogonal extension accommodated by the extensional system of the Granada Basin. The combination of geophysical, geodetic, and geological data reveals that the southwestern boundary of this extensional system is a seismically active compressional front extending from the W to the SW of the Granada Basin. The near-field Global Navigation Satellite System data determine NNE–SSW shortening of up to 2 mm/yr of the compressional front in the Zafarraya Polje. In this setting, the normal Ventas de Zafarraya Fault developed as a result of the bending-moment extension of the Sierra de Alhama antiform and was last reactivated during the 1884 Andalusian earthquake (Mw 6.5). The uplift in the central Betic Cordillera together with the subsidence in the Western Alborán Basin may facilitate a westward to southwestward gravitational collapse through the extensional detachment of the Granada Basin. The heterogeneous crust of the Betic Cordillera would generate the compressional front, which is divided into two sectors: thrusting to the west, and folding associated with buttressing to the south. Our results evidence that basal detachments, linking extensional fault activity with compressional fronts, may determine the activity of local surface structures and the geological hazard in densely populated regions.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"18 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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