Mateus Rodrigues de Vargas, Julie Tugend, Geoffroy Mohn, Nick Kusznir, Lin Liang-Fu
We investigate the crustal structure of the Northeastern (NE) South China Sea (SCS) rifted margin to constrain its crustal thickness and basement nature with implications for the Mesozoic and Cenozoic evolution of the SCS. First-order interfaces interpreted from seismic reflection data were integrated into a 3D gravity inversion scheme to determine Moho depth and crustal thickness variations. A joint inversion of seismic and gravity data allowed us to determine crustal density variations along 2D profiles. The distal margin of the NE SCS is divided into two distinct crustal domains: the Southern Rift System (SRS), and the Southern High (SH). The SRS shows an extremely thinned crust on top of which thick Cenozoic sequences are observed. It is separated from the oceanic crust (∼6–8 km thick) by the SH, a comparatively thicker crustal domain (∼10–15 km thick) with significant magmatic additions. The distal NE SCS margin formed during the Cenozoic rifting of the SCS. The SH likely corresponds to a polygenic piece of crust, recording polyphase magmatic activity since the Mesozoic, with potentially significant activity during Cenozoic post-rift time. The NE SCS margin is conjugate to Palawan whose basement is considered to be part of the exotic Luconia microcontinent that collided with Eurasia during the Late Cretaceous. Basement similarities between Palawan and the SH are highlighted, suggesting that the latter might also be part of Luconia. Our results suggest that the docking/suture zone between Eurasia and Luconia might have acted as a preferred zone for the Cenozoic rift development.
{"title":"Crustal Structure of the Northeast South China Sea Rifted Margin","authors":"Mateus Rodrigues de Vargas, Julie Tugend, Geoffroy Mohn, Nick Kusznir, Lin Liang-Fu","doi":"10.1029/2024tc008399","DOIUrl":"https://doi.org/10.1029/2024tc008399","url":null,"abstract":"We investigate the crustal structure of the Northeastern (NE) South China Sea (SCS) rifted margin to constrain its crustal thickness and basement nature with implications for the Mesozoic and Cenozoic evolution of the SCS. First-order interfaces interpreted from seismic reflection data were integrated into a 3D gravity inversion scheme to determine Moho depth and crustal thickness variations. A joint inversion of seismic and gravity data allowed us to determine crustal density variations along 2D profiles. The distal margin of the NE SCS is divided into two distinct crustal domains: the Southern Rift System (SRS), and the Southern High (SH). The SRS shows an extremely thinned crust on top of which thick Cenozoic sequences are observed. It is separated from the oceanic crust (∼6–8 km thick) by the SH, a comparatively thicker crustal domain (∼10–15 km thick) with significant magmatic additions. The distal NE SCS margin formed during the Cenozoic rifting of the SCS. The SH likely corresponds to a polygenic piece of crust, recording polyphase magmatic activity since the Mesozoic, with potentially significant activity during Cenozoic post-rift time. The NE SCS margin is conjugate to Palawan whose basement is considered to be part of the exotic Luconia microcontinent that collided with Eurasia during the Late Cretaceous. Basement similarities between Palawan and the SH are highlighted, suggesting that the latter might also be part of Luconia. Our results suggest that the docking/suture zone between Eurasia and Luconia might have acted as a preferred zone for the Cenozoic rift development.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"73 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209526","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}
Sedigheh Khodaparast, Saeed Madanipour, Eva Enkelmann, Khaled Hessami, Reza Nozaem
The collisional Iranian Plateau and its recent kinematic evolution represent a natural example to study the intraplate response to the transferred deformation from an active convergent plate margin. The late Cenozoic deformation and structural evolution of the Plateau is not well understood. Here, we integrate structural, tectonostratigraphic, and morphotectonic field observations with low-temperature thermochronometric data along the NW-SE trending Kushk-e-Nosrat (KN) Fault to unravel the exhumation history and the kinematic change at the northwestern boundary of the Iranian Plateau. We found different sets of strike-slip related structures along the KN Fault zone, which are classified into four categories based on their cross-cutting relations and the superimposition of kinematic indicators. These include dextral transtension, dextral, dextral transpression, and sinistral kinematics. The unreset zircon (U-Th)/He and apatite fission track results and the reset apatite (U-Th)/He data from the restraining area along the KN Fault suggest 80–60°C of cooling during the early Miocene (∼20–18 Ma) and late Miocene–early Pliocene (∼7–5 Ma) due to dextral and dextral transpressional kinematics along the KN Fault zone, respectively. The dextral transtentional faulting was recorded as deposition of the Qom Formation within the releasing overlap areas along the KN Fault at >20–18 Ma. The kinematics of the KN Fault changed to sinistral during Pliocene–Quaternary times presumably triggered by the simultaneous clockwise rotation of central Iran, Alborz Mountains, and the South Caspian block. Our study proposes that the morphological and tectonostratigraphic evolution of the northern margin of the Iranian Plateau has mainly been controlled through local uplift and exhumation in restraining areas and local thick deposition in releasing areas of the major strike-slip faults during the late Cenozoic time.
{"title":"Time Constraints on the Late Cenozoic Fault Evolution Along the Northern Margin of the Iranian Plateau in the Arabia-Eurasia Collision Zone","authors":"Sedigheh Khodaparast, Saeed Madanipour, Eva Enkelmann, Khaled Hessami, Reza Nozaem","doi":"10.1029/2023tc008034","DOIUrl":"https://doi.org/10.1029/2023tc008034","url":null,"abstract":"The collisional Iranian Plateau and its recent kinematic evolution represent a natural example to study the intraplate response to the transferred deformation from an active convergent plate margin. The late Cenozoic deformation and structural evolution of the Plateau is not well understood. Here, we integrate structural, tectonostratigraphic, and morphotectonic field observations with low-temperature thermochronometric data along the NW-SE trending Kushk-e-Nosrat (KN) Fault to unravel the exhumation history and the kinematic change at the northwestern boundary of the Iranian Plateau. We found different sets of strike-slip related structures along the KN Fault zone, which are classified into four categories based on their cross-cutting relations and the superimposition of kinematic indicators. These include dextral transtension, dextral, dextral transpression, and sinistral kinematics. The unreset zircon (U-Th)/He and apatite fission track results and the reset apatite (U-Th)/He data from the restraining area along the KN Fault suggest 80–60°C of cooling during the early Miocene (∼20–18 Ma) and late Miocene–early Pliocene (∼7–5 Ma) due to dextral and dextral transpressional kinematics along the KN Fault zone, respectively. The dextral transtentional faulting was recorded as deposition of the Qom Formation within the releasing overlap areas along the KN Fault at >20–18 Ma. The kinematics of the KN Fault changed to sinistral during Pliocene–Quaternary times presumably triggered by the simultaneous clockwise rotation of central Iran, Alborz Mountains, and the South Caspian block. Our study proposes that the morphological and tectonostratigraphic evolution of the northern margin of the Iranian Plateau has mainly been controlled through local uplift and exhumation in restraining areas and local thick deposition in releasing areas of the major strike-slip faults during the late Cenozoic time.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"75 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209401","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}
Violeta Veliz-Borel, Vasiliki Mouslopoulou, Johannes Glodny, John Begg, Sabrina Metzger, Dimitris Sakellariou, Onno Oncken
Sets of marine terraces, sediments, and paleoshorelines are commonly found in forearc regions worldwide. A common assumption holds that crustal uplift prevents these features from littoral erosion. Here, we study the vertical deformation of Karpathos, a forearc island in the eastern Mediterranean, whose long axis extends at a high angle to the strike of the Hellenic Subduction System (HSS). We target three key coastal localities along the island to discuss spatial and temporal variability of vertical motion. We mapped sets of up to 19 marine terraces per locality, with elevations ranging from 1.5 to ∼350 masl. Ages for terraces and sediments are constrained by radiocarbon (<31 masl) and Sr-isotope (2–310 masl) dating, and range from 2.4 ka to ∼4.3 Ma. Data analysis shows that average uplift rates are up to two orders of magnitude faster over shorter (⪅100 ka) than longer (⪆100 ka) timescales, in agreement with other local and global data sets. Further, we find evidence for multiple marine reoccupations of late Pleistocene terraces, indicating that carbonate beachrock is often resistant to multiple interactions with sea-level. Neogene marine sequences that witness longer periods (∼4 Ma) show signs of alternating vertical motion. Using this novel data set, we explore the effects of various mechanisms (i.e., upper-plate normal faulting, splay-thrust faulting, basal underplating) on the spatial and temporal patterns of vertical deformation. Although the contribution of each mechanism to the net vertical deformation cannot be isolated with certainty, our results show that none alone could account for the observations.
{"title":"Exploring Uplift Mechanisms Across the Forearc of a Subduction System: Karpathos Island as a Natural Transect Across the Eastern Hellenic Margin","authors":"Violeta Veliz-Borel, Vasiliki Mouslopoulou, Johannes Glodny, John Begg, Sabrina Metzger, Dimitris Sakellariou, Onno Oncken","doi":"10.1029/2023tc008156","DOIUrl":"https://doi.org/10.1029/2023tc008156","url":null,"abstract":"Sets of marine terraces, sediments, and paleoshorelines are commonly found in forearc regions worldwide. A common assumption holds that crustal uplift prevents these features from littoral erosion. Here, we study the vertical deformation of Karpathos, a forearc island in the eastern Mediterranean, whose long axis extends at a high angle to the strike of the Hellenic Subduction System (HSS). We target three key coastal localities along the island to discuss spatial and temporal variability of vertical motion. We mapped sets of up to 19 marine terraces per locality, with elevations ranging from 1.5 to ∼350 masl. Ages for terraces and sediments are constrained by radiocarbon (<31 masl) and Sr-isotope (2–310 masl) dating, and range from 2.4 ka to ∼4.3 Ma. Data analysis shows that average uplift rates are up to two orders of magnitude faster over shorter (⪅100 ka) than longer (⪆100 ka) timescales, in agreement with other local and global data sets. Further, we find evidence for multiple marine reoccupations of late Pleistocene terraces, indicating that carbonate beachrock is often resistant to multiple interactions with sea-level. Neogene marine sequences that witness longer periods (∼4 Ma) show signs of alternating vertical motion. Using this novel data set, we explore the effects of various mechanisms (i.e., upper-plate normal faulting, splay-thrust faulting, basal underplating) on the spatial and temporal patterns of vertical deformation. Although the contribution of each mechanism to the net vertical deformation cannot be isolated with certainty, our results show that none alone could account for the observations.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"102 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209525","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}
The Mauléon basin is a world-class example of hyperextended rift suture. The basin possesses key attributes of an optimal hydrogen target, namely mantle, at shallow depth with tectonic structures rooted into it. Natural H2 seepages have been recognized at the surface in the foothills. Yet distribution and quantification of serpentinization within the mantel piece representing the potential H2 source has not been addressed while this aspect is crucial to consider further exploration. We discuss these aspects using joint gravimetric and magnetic 2D forward modeling along two orthogonal transects. 2D forward modeling shows that serpentinization gradually increases from bottom (20 km depth) to top reaching a maximum amount of nearly 76% (8 km depth). The N-S transect evidence that serpentinization fronts are northward inclined, suggesting a N-S serpentinization gradient responsible for the long wavelength gravity and magnetic anomalies. This orientation matches that of detachment within the former hyperextended domain, which exhumed the mantle during the Cretaceous. The W-E transect shows that serpentinization also increase toward the east reaching its maximum amount against the Barlanès lithospheric structure. The latter also coincides with the main short wavelength magnetic anomaly recognized in the basin. Forward geophysical modeling reveals that this anomaly could be linked to the presence, at shallow depth, of an alkaline magmatic body or a shallower piece of highly serpentinized subcontinental mantle both attesting for the paroxysm of the Cretaceous rifting phase. Finally, we propose a conceptual model of the H2 life cycle in the Mauléon basin and discuss the implications for H2 exploration.
{"title":"Serpentinization and Magmatic Distribution in a Hyperextended Rift Suture: Implication for Natural Hydrogen Exploration (Mauléon Basin, Pyrenees)","authors":"N. Saspiturry, C. Allanic, A. Peyrefitte","doi":"10.1029/2024tc008385","DOIUrl":"https://doi.org/10.1029/2024tc008385","url":null,"abstract":"The Mauléon basin is a world-class example of hyperextended rift suture. The basin possesses key attributes of an optimal hydrogen target, namely mantle, at shallow depth with tectonic structures rooted into it. Natural H2 seepages have been recognized at the surface in the foothills. Yet distribution and quantification of serpentinization within the mantel piece representing the potential H2 source has not been addressed while this aspect is crucial to consider further exploration. We discuss these aspects using joint gravimetric and magnetic 2D forward modeling along two orthogonal transects. 2D forward modeling shows that serpentinization gradually increases from bottom (20 km depth) to top reaching a maximum amount of nearly 76% (8 km depth). The N-S transect evidence that serpentinization fronts are northward inclined, suggesting a N-S serpentinization gradient responsible for the long wavelength gravity and magnetic anomalies. This orientation matches that of detachment within the former hyperextended domain, which exhumed the mantle during the Cretaceous. The W-E transect shows that serpentinization also increase toward the east reaching its maximum amount against the Barlanès lithospheric structure. The latter also coincides with the main short wavelength magnetic anomaly recognized in the basin. Forward geophysical modeling reveals that this anomaly could be linked to the presence, at shallow depth, of an alkaline magmatic body or a shallower piece of highly serpentinized subcontinental mantle both attesting for the paroxysm of the Cretaceous rifting phase. Finally, we propose a conceptual model of the H2 life cycle in the Mauléon basin and discuss the implications for H2 exploration.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"8 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209529","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}
The High-Pressure Phyllites-Quartzites (PQ) unit of the External Hellenides is exposed in tectonic windows in the central and northern Peloponnese (Greece). Understanding the deformation history of this unit is essential to interpreting the Oligo-Miocene evolution of the External Hellenides belt and its associated exhumation events. This study integrates new field observations and microtectonic analyses with previous studies to offer a comprehensive deformation model of the PQ unit since the Late Oligocene. The first deformation phase (D1), captures the progressive incorporation of the PQ into an orogenic wedge. This phase is largely overprinted and only preserved as relict features. The second phase (D2) displays coeval top-to-the-ENE and top-to-the-WSW localized ductile shear. A transition is observed from top-to-the-ENE non-coaxial deformation at the upper parts of the nappe to intense isoclinal folding (refolding S1) at the lower structural levels. We associate D2 with the ductile syn-orogenic exhumation of the PQ within an extrusion wedge, accompanied by greenschist-facies retrogression. In the third phase (D3), semi-brittle to brittle extensional fault planes cut through the previous ductile structures. D3 faults exhibit extensional kinematics in all directions on the flanks of exhumation domes. This phase correlates with a late-orogenic doming event, marking the final exhumation stage of the PQ unit in the upper crust. The exhumation of high-pressure units results from the interplay between ductile syn-orogenic extrusion and continuous underplating within the subduction zone. This underplating maintains vertical movements and uplift of the units, initiating a 3D upper-crustal extensional collapse along low-angle normal faults.
{"title":"Deformation Mechanisms During the Syn-Orogenic Extrusion of the High-Pressure Phyllites-Quartzites Unit in the Central and Northern Peloponnese, Greece","authors":"Vincent Wicker, Simon Bufféral","doi":"10.1029/2023tc008116","DOIUrl":"https://doi.org/10.1029/2023tc008116","url":null,"abstract":"The High-Pressure Phyllites-Quartzites (PQ) unit of the External Hellenides is exposed in tectonic windows in the central and northern Peloponnese (Greece). Understanding the deformation history of this unit is essential to interpreting the Oligo-Miocene evolution of the External Hellenides belt and its associated exhumation events. This study integrates new field observations and microtectonic analyses with previous studies to offer a comprehensive deformation model of the PQ unit since the Late Oligocene. The first deformation phase (D<sub>1</sub>), captures the progressive incorporation of the PQ into an orogenic wedge. This phase is largely overprinted and only preserved as relict features. The second phase (D<sub>2</sub>) displays coeval top-to-the-ENE and top-to-the-WSW localized ductile shear. A transition is observed from top-to-the-ENE non-coaxial deformation at the upper parts of the nappe to intense isoclinal folding (refolding S<sub>1</sub>) at the lower structural levels. We associate D<sub>2</sub> with the ductile syn-orogenic exhumation of the PQ within an extrusion wedge, accompanied by greenschist-facies retrogression. In the third phase (D<sub>3</sub>), semi-brittle to brittle extensional fault planes cut through the previous ductile structures. D<sub>3</sub> faults exhibit extensional kinematics in all directions on the flanks of exhumation domes. This phase correlates with a late-orogenic doming event, marking the final exhumation stage of the PQ unit in the upper crust. The exhumation of high-pressure units results from the interplay between ductile syn-orogenic extrusion and continuous underplating within the subduction zone. This underplating maintains vertical movements and uplift of the units, initiating a 3D upper-crustal extensional collapse along low-angle normal faults.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"19 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209399","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}
Yanling Zhang, Changqing Yin, Lin Ding, Shun Li, Jiahui Qian, Peng Gao, Wangchao Li
Despite a half-century of intense research, the timing and diachroneity of initial collision between India and Asia remain highly debated, largely due to different definitions of “initial collision” and correspondingly different methods adopted. This study focuses on high-pressure pelitic granulites of the Eastern Himalayan Syntaxis (EHS) to elucidate their metamorphic evolution and provide new constraints on the timing of initial India-Asia collision. Petrological examination and phase equilibria modeling show that high-pressure pelitic granulites have undergone four metamorphic stages, with the peak assemblage of garnet + K-feldspar + kyanite + biotite ± plagioclase ± rutile + ilmenite + quartz at P-T conditions of 13.1–15.7 kbar and 790–850°C. Clockwise P-T paths suggest that the Indian continent underwent tectonometamorphic processes of initial collision and subsequent continent subduction. Zircon and monazite dating results indicate that the metamorphic ages of pelitic granulites range from 60 to 15 Ma, with the oldest ones clustered at 60–58 Ma. The oldest metamorphic ages of high- to ultrahigh-pressure Himalayan metamorphic rocks can provide an upper age limit of the initial collision. Therefore, the initial India-Asia collision must have occurred before 60–58 Ma in the EHS, roughly consistent with ca. 57 Ma in the western Himalaya and 63–60 Ma in the central Himalaya. Collectively, we conclude that the northern margin of India most likely underwent a single-stage synchronous collision with the southern margin of Asia initially at around 60 Ma along the entire Yarlung-Tsangpo suture zone.
尽管经过半个世纪的深入研究，印度和亚洲之间最初碰撞的时间和非同步性仍然存在很大争议，这主要是由于对 "最初碰撞 "的定义不同，相应采用的方法也不同。本研究以东喜马拉雅山系（EHS）的高压辉绿岩花岗岩为研究对象，旨在阐明其变质演化过程，并为印度与亚洲的初始碰撞时间提供新的约束条件。岩石学检查和相平衡模型显示，高压辉绿岩花岗岩经历了四个变质阶段，在13.1-15.7千巴和790-850°C的P-T条件下，石榴石+K长石+闪长岩+生物橄榄石±斜长石±金红石+钛铁矿+石英的组合达到顶峰。顺时针的P-T路径表明，印度大陆经历了最初的碰撞和随后的大陆俯冲的构造变质过程。锆石和独居石测年结果表明，辉绿岩花岗岩的变质年龄在60-15Ma之间，最古老的集中在60-58Ma。喜马拉雅山高压至超高压变质岩的最古老变质年龄可以提供初始碰撞的年龄上限。因此，最初的印度-亚洲碰撞一定发生在 EHS 的 60-58 Ma 之前，与喜马拉雅西部的约 57 Ma 和喜马拉雅中部的 63-60 Ma 大致吻合。综上所述，我们得出结论，印度北缘很可能在60Ma左右时沿整个雅鲁藏布江缝合带与亚洲南缘发生了单阶段同步碰撞。
{"title":"Single-Stage Synchronous India-Asia Collision Model Revealed by Himalayan High-Pressure Metamorphic Rocks","authors":"Yanling Zhang, Changqing Yin, Lin Ding, Shun Li, Jiahui Qian, Peng Gao, Wangchao Li","doi":"10.1029/2024tc008253","DOIUrl":"https://doi.org/10.1029/2024tc008253","url":null,"abstract":"Despite a half-century of intense research, the timing and diachroneity of initial collision between India and Asia remain highly debated, largely due to different definitions of “initial collision” and correspondingly different methods adopted. This study focuses on high-pressure pelitic granulites of the Eastern Himalayan Syntaxis (EHS) to elucidate their metamorphic evolution and provide new constraints on the timing of initial India-Asia collision. Petrological examination and phase equilibria modeling show that high-pressure pelitic granulites have undergone four metamorphic stages, with the peak assemblage of garnet + K-feldspar + kyanite + biotite ± plagioclase ± rutile + ilmenite + quartz at <i>P</i>-<i>T</i> conditions of 13.1–15.7 kbar and 790–850°C. Clockwise <i>P</i>-<i>T</i> paths suggest that the Indian continent underwent tectonometamorphic processes of initial collision and subsequent continent subduction. Zircon and monazite dating results indicate that the metamorphic ages of pelitic granulites range from 60 to 15 Ma, with the oldest ones clustered at 60–58 Ma. The oldest metamorphic ages of high- to ultrahigh-pressure Himalayan metamorphic rocks can provide an upper age limit of the initial collision. Therefore, the initial India-Asia collision must have occurred before 60–58 Ma in the EHS, roughly consistent with ca. 57 Ma in the western Himalaya and 63–60 Ma in the central Himalaya. Collectively, we conclude that the northern margin of India most likely underwent a single-stage synchronous collision with the southern margin of Asia initially at around 60 Ma along the entire Yarlung-Tsangpo suture zone.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"47 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209528","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}
Haomin Ji, Zhikun Ren, Xiaoxiao Zhu, Mingkun Bai, Guodong Bao, Jinrui Liu, Guanghao Ha, Zhongtai He
The tectonic deformation of the southeastern margin of the Tibetan Plateau underwent significant changes before and after the Miocene, which led to the change of the deformation characteristics of the Sichuan-Yunnan block, and some local areas in the block also showed structural patterns inconsistent with the macroscopic clockwise rotation deformation. Moreover, the Chenghai fault (CF) in the Sichuan-Yunnan block was the seismogenic fault of the M 73/4 Yongsheng earthquake in 1515. However, the dense vegetation impeded the acquisition of surface deformation characteristics and small-scale horizontal offsets along the fault, resulting in its misty kinematic properties, roughly determined geometric distribution, and the highly controversial rupture parameters of the Yongsheng earthquake. Therefore, we used airborne light detection and ranging, which can penetrate vegetation to obtain high-resolution surface topography, to map the CF within 120 km. Combined with satellite images and field investigations, we determined that the CF consists of a series of secondary faults with simple geometric structures. Continuous offset linear landforms were preserved along the fault. 102 offsets below 30 m were statistically analyzed and the result revealed that the CF has a characteristic displacement of ∼6 m and it may rupture as a united rupture segment in each large earthquake or its two rupture segments cascade rupture to generate large earthquakes. The magnitude of the Yongsheng earthquake in 1515 was estimated at 7.7. Finally, based on this study, the kinematic characteristics of the Dali terrane and Sichuan-Yunnan block, where the CF is located are discussed.
{"title":"Slip Distribution Along the Chenghai Fault From Airborne LiDAR and Tectonic Implications for the 1515 Yongsheng Earthquake, China","authors":"Haomin Ji, Zhikun Ren, Xiaoxiao Zhu, Mingkun Bai, Guodong Bao, Jinrui Liu, Guanghao Ha, Zhongtai He","doi":"10.1029/2024tc008285","DOIUrl":"https://doi.org/10.1029/2024tc008285","url":null,"abstract":"The tectonic deformation of the southeastern margin of the Tibetan Plateau underwent significant changes before and after the Miocene, which led to the change of the deformation characteristics of the Sichuan-Yunnan block, and some local areas in the block also showed structural patterns inconsistent with the macroscopic clockwise rotation deformation. Moreover, the Chenghai fault (CF) in the Sichuan-Yunnan block was the seismogenic fault of the M 7<sup>3</sup>/<sub>4</sub> Yongsheng earthquake in 1515. However, the dense vegetation impeded the acquisition of surface deformation characteristics and small-scale horizontal offsets along the fault, resulting in its misty kinematic properties, roughly determined geometric distribution, and the highly controversial rupture parameters of the Yongsheng earthquake. Therefore, we used airborne light detection and ranging, which can penetrate vegetation to obtain high-resolution surface topography, to map the CF within 120 km. Combined with satellite images and field investigations, we determined that the CF consists of a series of secondary faults with simple geometric structures. Continuous offset linear landforms were preserved along the fault. 102 offsets below 30 m were statistically analyzed and the result revealed that the CF has a characteristic displacement of ∼6 m and it may rupture as a united rupture segment in each large earthquake or its two rupture segments cascade rupture to generate large earthquakes. The magnitude of the Yongsheng earthquake in 1515 was estimated at 7.7. Finally, based on this study, the kinematic characteristics of the Dali terrane and Sichuan-Yunnan block, where the CF is located are discussed.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"35 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141933222","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}
Ali Niknam, Annique van der Boon, Mahnaz Rezaeian, Nuretdin Kaymakcı, Cor Langereis
Northwest Iran is a seismically active region dominated by NW-SE trending strike-slip faults, such as the North Tabriz and Qosha Dagh faults, and smaller NNE-SSW striking faults. The Bozgush Mountains are shaped by these faults and divided into two domains that show a difference in strike. To quantify rotational tectonic deformation in NW Iran, we performed a paleomagnetic study along three transects of the Bozgush and Qosha Dagh Mountains with 127 sites. Our large new paleomagnetic data set shows that the Bozgush Mountains did not rotate as a single rigid block. In the western domain of the Bozgush Mountains, we find evidence for clockwise vertical axis rotations of ∼40°, while the eastern domain has rotated up to ∼80° clockwise. Declinations of the western Bozgush domain fit well with observed declinations in the Qosha Dagh Mountains. Fault patterns show that the eastern domain of the Bozgush Mountains is divided by a set of NNE-SSW striking sinistral strike-slip faults, which created domino-style blocks that accommodated the additional 40° of rotation. We estimate that these extra rotations have resulted in around 4 km of N-S shortening and more than 1.5 km of differential uplift.
{"title":"Block Rotations in NW Iran in Response to the Arabia-Eurasia Collision Constrained by Paleomagnetism","authors":"Ali Niknam, Annique van der Boon, Mahnaz Rezaeian, Nuretdin Kaymakcı, Cor Langereis","doi":"10.1029/2023tc008139","DOIUrl":"https://doi.org/10.1029/2023tc008139","url":null,"abstract":"Northwest Iran is a seismically active region dominated by NW-SE trending strike-slip faults, such as the North Tabriz and Qosha Dagh faults, and smaller NNE-SSW striking faults. The Bozgush Mountains are shaped by these faults and divided into two domains that show a difference in strike. To quantify rotational tectonic deformation in NW Iran, we performed a paleomagnetic study along three transects of the Bozgush and Qosha Dagh Mountains with 127 sites. Our large new paleomagnetic data set shows that the Bozgush Mountains did not rotate as a single rigid block. In the western domain of the Bozgush Mountains, we find evidence for clockwise vertical axis rotations of ∼40°, while the eastern domain has rotated up to ∼80° clockwise. Declinations of the western Bozgush domain fit well with observed declinations in the Qosha Dagh Mountains. Fault patterns show that the eastern domain of the Bozgush Mountains is divided by a set of NNE-SSW striking sinistral strike-slip faults, which created domino-style blocks that accommodated the additional 40° of rotation. We estimate that these extra rotations have resulted in around 4 km of N-S shortening and more than 1.5 km of differential uplift.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"3 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141933224","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}
The accommodation of the substantial eastward crustal motion of the Bayan Har block characterizes the dynamics of faults located at the eastern Tibetan Plateau. However, uncertainties persist concerning the manner and amount of deformation distributed on these faults, with slip senses and rates constituting critical factors. In the northeastern segment of the Longmenshan thrust zone, the contentious activity and the unknown geologic slip rate present challenges. This study, focusing on the Qingchuan fault, the predominant fault within the northeastern Longmenshan, employed satellite imagery interpretation, displaced fluvial terraces surveying, displacement measurements, and chronological analysis to comprehensively characterize its fault activity. Our investigation robustly demonstrates the Qingchuan fault has been active since the late Quaternary, and is primarily marked with a pronounced dextral slip at a rate of 0.6–1.0 mm/year. By quantitatively assessing the deformation rates of the faults at the eastern Tibetan Plateau, we propose that they sufficiently accommodate the entire eastward crustal movement of the Bayan Har block; thereby no additional deformation propagates beyond the Qingchuan fault. Furthermore, we introduce a subblock model to elucidate the regional crustal deformation pattern, wherein the eastward movement of the Bayan Har block transfers to the northeastward movement of the Bikou subblock. This movement results in reverse slip patterns for the Minjiang and Huya faults, while the Beichuan and Qingchuan faults predominantly experience dextral displacements. The complex strain partitioning within the northern Longmenshan range underscores the observed variations in slip patterns across different segments of the Longmenshan thrust zone, advancing our understanding of fault behavior and the orchestration of crustal deformation in this intricate tectonic framework.
{"title":"Kinematics Along the Qingchuan Fault and Deformation Pattern in the Eastern Tibetan Plateau","authors":"Haoyue Sun, Honglin He, Yasutaka Ikeda, Ken'ichi Kano, Wei Gao, Wen Sun, Feng Shi, Peng Su, Tomoo Echigo, Shinsuke Okada, Yoshiki Shirahama","doi":"10.1029/2023tc008075","DOIUrl":"https://doi.org/10.1029/2023tc008075","url":null,"abstract":"The accommodation of the substantial eastward crustal motion of the Bayan Har block characterizes the dynamics of faults located at the eastern Tibetan Plateau. However, uncertainties persist concerning the manner and amount of deformation distributed on these faults, with slip senses and rates constituting critical factors. In the northeastern segment of the Longmenshan thrust zone, the contentious activity and the unknown geologic slip rate present challenges. This study, focusing on the Qingchuan fault, the predominant fault within the northeastern Longmenshan, employed satellite imagery interpretation, displaced fluvial terraces surveying, displacement measurements, and chronological analysis to comprehensively characterize its fault activity. Our investigation robustly demonstrates the Qingchuan fault has been active since the late Quaternary, and is primarily marked with a pronounced dextral slip at a rate of 0.6–1.0 mm/year. By quantitatively assessing the deformation rates of the faults at the eastern Tibetan Plateau, we propose that they sufficiently accommodate the entire eastward crustal movement of the Bayan Har block; thereby no additional deformation propagates beyond the Qingchuan fault. Furthermore, we introduce a subblock model to elucidate the regional crustal deformation pattern, wherein the eastward movement of the Bayan Har block transfers to the northeastward movement of the Bikou subblock. This movement results in reverse slip patterns for the Minjiang and Huya faults, while the Beichuan and Qingchuan faults predominantly experience dextral displacements. The complex strain partitioning within the northern Longmenshan range underscores the observed variations in slip patterns across different segments of the Longmenshan thrust zone, advancing our understanding of fault behavior and the orchestration of crustal deformation in this intricate tectonic framework.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"77 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141933165","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}
The present tectonic regime of the Qilian Shan is dominated by large northeast and northwest striking strike-slip faults and northwest striking thrust faults. Deformation distribution between the subparallel Haiyuan Strike-slip Fault and the Minle-Damaying Thrust Fault (MDF) is crucial for understanding the orogenic mechanism of the northeastern Tibetan Plateau. However, the uncertain kinematics of the MDF and the stress variation along the strike-varying Haiyuan Fault inhibit further discussion of their relationship. Five key sites along the MDF were selected for analysis of terrace abandonment ages and vertical offsets to determine the slip rates. Two finite element models were constructed to calculate the stress-strain relationship between the Haiyuan Fault and MDF. We find that the activity of the MDF can be divided into two segments by a stepover with less activity and lower terrain at the Xida River site. Shortening rates of the MDF vary between 0.2 and 2.4 mm/a since the late Pleistocene with trapezoidal trends on both fault segments. The two finite element models and GPS data reveal that the strain rates are lower at the Xida River site but higher at the Menyuan Bend on the Haiyuan Fault. We infer that long-term strain accumulation at the Menyuan Bend may have mitigated the tectonic activity northeast to the bend under the northeastward stress field, including the activity of the MDF at the Xida River site, and resulted in the segmentation of the MDF.
{"title":"The Bend on the Haiyuan Strike-Slip Fault Leads to Segmented Activity of the Minle-Damaying Thrust Fault in the Qilian Shan, the Northeastern Tibetan Plateau","authors":"Qingri Liu, Jianguo Xiong, Peizhen Zhang, Wei Tao, Luyuan Huang, Xuhang Yang, Yihui Zhang, Feipeng Huang, Xiuli Zhang, Huiping Zhang, Chuanyou Li, Youli Li","doi":"10.1029/2023tc008239","DOIUrl":"https://doi.org/10.1029/2023tc008239","url":null,"abstract":"The present tectonic regime of the Qilian Shan is dominated by large northeast and northwest striking strike-slip faults and northwest striking thrust faults. Deformation distribution between the subparallel Haiyuan Strike-slip Fault and the Minle-Damaying Thrust Fault (MDF) is crucial for understanding the orogenic mechanism of the northeastern Tibetan Plateau. However, the uncertain kinematics of the MDF and the stress variation along the strike-varying Haiyuan Fault inhibit further discussion of their relationship. Five key sites along the MDF were selected for analysis of terrace abandonment ages and vertical offsets to determine the slip rates. Two finite element models were constructed to calculate the stress-strain relationship between the Haiyuan Fault and MDF. We find that the activity of the MDF can be divided into two segments by a stepover with less activity and lower terrain at the Xida River site. Shortening rates of the MDF vary between 0.2 and 2.4 mm/a since the late Pleistocene with trapezoidal trends on both fault segments. The two finite element models and GPS data reveal that the strain rates are lower at the Xida River site but higher at the Menyuan Bend on the Haiyuan Fault. We infer that long-term strain accumulation at the Menyuan Bend may have mitigated the tectonic activity northeast to the bend under the northeastward stress field, including the activity of the MDF at the Xida River site, and resulted in the segmentation of the MDF.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"191 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141933223","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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