Mervin J. Bartholomew, Demin Liu, Andrew M. Mickelson, Lian Brugere, Tammy Rittenour, Guo Q. Sun
The Yushu fault, part of the Yushu–Ganzi fault zone, is one of several E-W-trending left-lateral, strike-slip fault zones that extend across the Tibetan Plateau accommodating lateral transfer of crustal material out of the collision zone between the Indian and Eurasian plates. Discontinuous left-lateral surface rupture occurred along WNW-ESE-striking, near-vertical faults during two Mw 6.9 14 April 2010 Yushu earthquakes. Geomorphic and surface-rupture characteristics change at the base of a red cliff separating the Guoqiong and Buqionggei segments. Excavations across these segments near the Jinsha River show: (a) more continuous deposition on the down-dropped side; and (b) how frequently these surface-rupture histories were linked or sequential (major to great earthquakes) versus not linked (moderate/strong to large earthquakes). Trench CUG-2011-1 and roadcut CUG-2012-1 (Guoqiong segment) were on older fan surfaces and Trench CUG-2012-2 (Buqionggei segment) crossed a narrow graben. On the Guoqiong segment, using OxCal v.4.4 that works with IntCal20 database for Bayesian-ordered ages from four 14C and nine OSL ages, surface ruptures occurred during earthquakes at 2010CE, ∼200BCE, ∼2400BCE, ∼4250BCE, ∼6750BCE, ∼7400BCE and ∼10400BCE consistent with an ∼2200-year Holocene recurrence interval. For the Buqionggei segment, Bayesian-ordered ages from six OSL ages indicate three Holocene surface ruptures occurred at 2010CE, ∼4600BCE and ∼6750BCE. Surface ruptures on both segments (suggesting linked or sequential major to great earthquakes) only occurred two to three times at 2010CE, ∼4500BCE and/or ∼6750BCE. Thus, risk of infrequent major to great Holocene earthquakes is ∼2400–∼8800 years along the Yushu fault.
{"title":"Timing of Holocene Surface-Ruptures Across Adjacent Rupture-Segments Where the Jinsha River Crosses the Yushu Fault, Qinghai Province, China","authors":"Mervin J. Bartholomew, Demin Liu, Andrew M. Mickelson, Lian Brugere, Tammy Rittenour, Guo Q. Sun","doi":"10.1029/2023tc007922","DOIUrl":"https://doi.org/10.1029/2023tc007922","url":null,"abstract":"The Yushu fault, part of the Yushu–Ganzi fault zone, is one of several E-W-trending left-lateral, strike-slip fault zones that extend across the Tibetan Plateau accommodating lateral transfer of crustal material out of the collision zone between the Indian and Eurasian plates. Discontinuous left-lateral surface rupture occurred along WNW-ESE-striking, near-vertical faults during two Mw 6.9 14 April 2010 Yushu earthquakes. Geomorphic and surface-rupture characteristics change at the base of a red cliff separating the Guoqiong and Buqionggei segments. Excavations across these segments near the Jinsha River show: (a) more continuous deposition on the down-dropped side; and (b) how frequently these surface-rupture histories were linked or sequential (<i>major to great</i> earthquakes) versus not linked (<i>moderate/strong to large</i> earthquakes). Trench CUG-2011-1 and roadcut CUG-2012-1 (Guoqiong segment) were on older fan surfaces and Trench CUG-2012-2 (Buqionggei segment) crossed a narrow graben. On the Guoqiong segment, using OxCal v.4.4 that works with IntCal20 database for Bayesian-ordered ages from four <sup>14</sup>C and nine OSL ages, surface ruptures occurred during earthquakes at 2010CE, ∼200BCE, ∼2400BCE, ∼4250BCE, ∼6750BCE, ∼7400BCE and ∼10400BCE consistent with an ∼2200-year Holocene recurrence interval. For the Buqionggei segment, Bayesian-ordered ages from six OSL ages indicate three Holocene surface ruptures occurred at 2010CE, ∼4600BCE and ∼6750BCE. Surface ruptures on both segments (suggesting linked or sequential <i>major to great</i> earthquakes) only occurred two to three times at 2010CE, ∼4500BCE and/or ∼6750BCE. Thus, risk of infrequent <i>major to great</i> Holocene earthquakes is ∼2400–∼8800 years along the Yushu fault.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"35 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141551243","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}
R. Quiroga, L. Giambiagi, A. Echaurren, J. Mescua, H. Pingel, G. Fuentes, M. Peña, J. Suriano, F. Martínez, C. Mpodozis, M. R. Strecker
We present a study in the southern Puna (26°30′–27°30′S), aiming to explore the late Cenozoic evolution of the deformation and the stress field during its uplift. Through U-Pb geochronology, structural observations, paleostress analysis, and balanced cross-sections, we propose an structural evolutionary model over the past 24 million years, separated in four stages: Stage 1, in the late Oligocene to middle Miocene, the region experienced E-W compression. Stage 2, from middle to late Miocene, a transition from predominant compression to an incipient strike-slip regime is observed. Stage 3, from late Miocene to early Pliocene, showed a further shift in the stress field, resulting in a combination of a predominant strike-slip regime, and less predominant compressional regime. Finally, Stage 4, from late Pliocene to Quaternary, featured a dominance of strike-slip regimes. Our results show that the stress field in each stage is associated with the orogen's internal architecture and its evolution. Vertical stress variations are linked to plateau uplift, creating topographic gradients across the orogen. Horizontal rotations of the principal stress axes are caused mainly by an edge effect resulting from the growth of the plateau while it reaches a critical crustal thickness and elevation. This leads to a transfer of compression from high-lying areas to lower regions. The southernmost Puna region shows no significant evidence of normal faulting, suggesting it is not undergoing orogenic collapse associated with a regional tensional stress regime.
{"title":"Boundary Effects of Orogenic Plateaus in the Evolution of the Stress Field: The Southern Puna Study Case (26°30′–27°30′S)","authors":"R. Quiroga, L. Giambiagi, A. Echaurren, J. Mescua, H. Pingel, G. Fuentes, M. Peña, J. Suriano, F. Martínez, C. Mpodozis, M. R. Strecker","doi":"10.1029/2023tc008185","DOIUrl":"https://doi.org/10.1029/2023tc008185","url":null,"abstract":"We present a study in the southern Puna (26°30′–27°30′S), aiming to explore the late Cenozoic evolution of the deformation and the stress field during its uplift. Through U-Pb geochronology, structural observations, paleostress analysis, and balanced cross-sections, we propose an structural evolutionary model over the past 24 million years, separated in four stages: Stage 1, in the late Oligocene to middle Miocene, the region experienced E-W compression. Stage 2, from middle to late Miocene, a transition from predominant compression to an incipient strike-slip regime is observed. Stage 3, from late Miocene to early Pliocene, showed a further shift in the stress field, resulting in a combination of a predominant strike-slip regime, and less predominant compressional regime. Finally, Stage 4, from late Pliocene to Quaternary, featured a dominance of strike-slip regimes. Our results show that the stress field in each stage is associated with the orogen's internal architecture and its evolution. Vertical stress variations are linked to plateau uplift, creating topographic gradients across the orogen. Horizontal rotations of the principal stress axes are caused mainly by an edge effect resulting from the growth of the plateau while it reaches a critical crustal thickness and elevation. This leads to a transfer of compression from high-lying areas to lower regions. The southernmost Puna region shows no significant evidence of normal faulting, suggesting it is not undergoing orogenic collapse associated with a regional tensional stress regime.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"40 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508358","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}
A. Ceccato, W. M. Behr, A. S. Zappone, L. Tavazzani, A. Giuliani
The rheology of crystalline units controls the large-scale deformation geometry and dynamics of collisional orogens. Defining a time-constrained rheological evolution of such units may help unravel the details of collisional dynamics. Here, we integrate field analysis, pseudosection calculations and in situ garnet U–Pb and mica Rb–Sr geochronology to define the structural and rheological evolution of the Rotondo granite (Gotthard nappe, Central Alps). We identify a sequence of four (D1–D4) deformation stages. Pre-collisional D1 brittle faults developed before Alpine peak metamorphism, which occurred at 34–20 Ma (U–Pb garnet ages) at 590 ± 25°C and 0.9 ± 0.1 GPa. The reactivation of D1 structures controlled the rheological evolution, from D2 reverse mylonitic shearing at amphibolite facies (520 ± 40°C and 0.8 ± 0.1 GPa) at 18–20 Ma (white mica Rb–Sr ages), to strike-slip, brittle-ductile shearing at greenschist-facies D3 (395 ± 25°C and 0.4 ± 0.1 GPa) at 14–15 Ma (white mica and biotite Rb–Sr ages), and then to D4 strike-slip faulting at shallow conditions. Although highly misoriented for the Alpine collisional stress orientation, D1 brittle structures controlled the localization of D2 ductile mylonites accommodating fast (∼3 mm/yr) exhumation rates due to their weak shear strength (<10 MPa). This structural and rheological evolution is common across External Crystalline Massifs (e.g., Aar, Mont Blanc), suggesting that the European upper crust was extremely weak during Alpine collision, its strength controlled by weak ductile shear zones localized on pre-collisional deformation structures, that in turn controlled localized exhumation at the scale of the orogen.
{"title":"Structural Evolution, Exhumation Rates, and Rheology of the European Crust During Alpine Collision: Constraints From the Rotondo Granite—Gotthard Nappe","authors":"A. Ceccato, W. M. Behr, A. S. Zappone, L. Tavazzani, A. Giuliani","doi":"10.1029/2023tc008219","DOIUrl":"https://doi.org/10.1029/2023tc008219","url":null,"abstract":"The rheology of crystalline units controls the large-scale deformation geometry and dynamics of collisional orogens. Defining a time-constrained rheological evolution of such units may help unravel the details of collisional dynamics. Here, we integrate field analysis, pseudosection calculations and in situ garnet U–Pb and mica Rb–Sr geochronology to define the structural and rheological evolution of the Rotondo granite (Gotthard nappe, Central Alps). We identify a sequence of four (D<sub>1</sub>–D<sub>4</sub>) deformation stages. Pre-collisional D<sub>1</sub> brittle faults developed before Alpine peak metamorphism, which occurred at 34–20 Ma (U–Pb garnet ages) at 590 ± 25°C and 0.9 ± 0.1 GPa. The reactivation of D<sub>1</sub> structures controlled the rheological evolution, from D<sub>2</sub> reverse mylonitic shearing at amphibolite facies (520 ± 40°C and 0.8 ± 0.1 GPa) at 18–20 Ma (white mica Rb–Sr ages), to strike-slip, brittle-ductile shearing at greenschist-facies D<sub>3</sub> (395 ± 25°C and 0.4 ± 0.1 GPa) at 14–15 Ma (white mica and biotite Rb–Sr ages), and then to D<sub>4</sub> strike-slip faulting at shallow conditions. Although highly misoriented for the Alpine collisional stress orientation, D<sub>1</sub> brittle structures controlled the localization of D<sub>2</sub> ductile mylonites accommodating fast (∼3 mm/yr) exhumation rates due to their weak shear strength (<10 MPa). This structural and rheological evolution is common across External Crystalline Massifs (e.g., Aar, Mont Blanc), suggesting that the European upper crust was extremely weak during Alpine collision, its strength controlled by weak ductile shear zones localized on pre-collisional deformation structures, that in turn controlled localized exhumation at the scale of the orogen.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"193 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508359","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 interplay between regional tectonics and the development of a major ocean gateway between the Pacific and the Atlantic Ocean has resulted in numerous paleogeographic reconstruction studies that describe the Cenozoic tectonic history of the Scotia Sea region. Despite the multitude of published tectonic reconstructions and the variety of geological and geophysical data available from the Scotia Sea, the geological history remains ambiguous. We present a comparative paleogeographic analysis of previously published tectonic reconstructions to identify agreements and conflicts between these reconstructions. We propose an alternative model to explain the Cenozoic evolution of the Scotia Sea region. The paleogeographic comparison shows that most reconstructions agree on the tectonic evolution of the South Scotia Ridge and the East Scotia Ridge. Major differences between the reconstructions are the role of the westward subducting plate below the South Sandwich plate, and the age and origin of the Central Scotia Sea. Tectonic reconstructions assume that the Central Scotia Sea is either part of a Cenozoic back-arc basin, or a captured piece of Cretaceous oceanic crust. We propose a new alternative tectonic reconstruction that brings these two prevailing hypotheses elegantly together. Here, we identified new geographical blocks consisting of thinned continental or Cretaceous oceanic fragments that originate from the Paleo-Pacific Weddell Sea gateway from high-resolution bathymetry. These fragments are now part of the Central Scotia Sea and have been affected by early back-arc tectonic activity of the South Sandwich subduction zone, leading locally to the formation of Cenozoic-aged crust in the Central Scotia Sea.
{"title":"Cretaceous Crust in the Scotia Sea: Missing Pieces in a Geological Puzzle?","authors":"J. H. Oldenhage, W. P. Schellart, A. Beniest","doi":"10.1029/2023tc008079","DOIUrl":"https://doi.org/10.1029/2023tc008079","url":null,"abstract":"The interplay between regional tectonics and the development of a major ocean gateway between the Pacific and the Atlantic Ocean has resulted in numerous paleogeographic reconstruction studies that describe the Cenozoic tectonic history of the Scotia Sea region. Despite the multitude of published tectonic reconstructions and the variety of geological and geophysical data available from the Scotia Sea, the geological history remains ambiguous. We present a comparative paleogeographic analysis of previously published tectonic reconstructions to identify agreements and conflicts between these reconstructions. We propose an alternative model to explain the Cenozoic evolution of the Scotia Sea region. The paleogeographic comparison shows that most reconstructions agree on the tectonic evolution of the South Scotia Ridge and the East Scotia Ridge. Major differences between the reconstructions are the role of the westward subducting plate below the South Sandwich plate, and the age and origin of the Central Scotia Sea. Tectonic reconstructions assume that the Central Scotia Sea is either part of a Cenozoic back-arc basin, or a captured piece of Cretaceous oceanic crust. We propose a new alternative tectonic reconstruction that brings these two prevailing hypotheses elegantly together. Here, we identified new geographical blocks consisting of thinned continental or Cretaceous oceanic fragments that originate from the Paleo-Pacific Weddell Sea gateway from high-resolution bathymetry. These fragments are now part of the Central Scotia Sea and have been affected by early back-arc tectonic activity of the South Sandwich subduction zone, leading locally to the formation of Cenozoic-aged crust in the Central Scotia Sea.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"12 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508360","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}
Max M. Garvue, James A. Spotila, Michele L. Cooke, Elizabeth R. Curtiss
Restraining bends influence topography, strike-slip evolution, and earthquake rupture dynamics, however the specific factors governing their geometry and development in the crust are not well established. These relationships are challenging to investigate in field examples due to cannibalization and erosion of earlier structures with cumulative strain. To address this knowledge gap, we investigated the structure, morphology, and kinematics of 22 basement-cored restraining bends on low net-slip faults (<10 km) within the southern Eastern California shear zone (SECSZ) via mapping, topographic analyses, and 3D numerical modeling. The bends are self-similar in form with most exhibiting focused relief between high-angle bounding faults with an arrowhead shape in map view and a “whaleback” longitudinal profile. Slight changes in that form occur with increasing size indicating predictable growth that appears to be primarily controlled by local fault geometries (i.e., bifurcation angle), rather than the influence of fault obliquity relative to far-field plate motion, due to inefficient slip-transfer across interconnected irregularly trending closely spaced faults. Modeling results indicate that the self-similar fault-bound geometry of SECSZ restraining bends may arise from elevated shear strain at the outer corners of single transpressional fault bends with increasing cumulative slip. This, in turn, promotes growth of a new fault leading to efficient accommodation of local convergent strain via uplift between bounding faults. Finally, our results indicate that the kilometer-scale restraining bends contribute minimally to regional contraction as they only penetrate the upper third of the seismogenic crust and are therefore also unlikely to impede large earthquake surface ruptures.
{"title":"What Controls Early Restraining Bend Growth? Structural, Morphometric, and Numerical Modeling Analyses From the Eastern California Shear Zone","authors":"Max M. Garvue, James A. Spotila, Michele L. Cooke, Elizabeth R. Curtiss","doi":"10.1029/2023tc008148","DOIUrl":"https://doi.org/10.1029/2023tc008148","url":null,"abstract":"Restraining bends influence topography, strike-slip evolution, and earthquake rupture dynamics, however the specific factors governing their geometry and development in the crust are not well established. These relationships are challenging to investigate in field examples due to cannibalization and erosion of earlier structures with cumulative strain. To address this knowledge gap, we investigated the structure, morphology, and kinematics of 22 basement-cored restraining bends on low net-slip faults (<10 km) within the southern Eastern California shear zone (SECSZ) via mapping, topographic analyses, and 3D numerical modeling. The bends are self-similar in form with most exhibiting focused relief between high-angle bounding faults with an arrowhead shape in map view and a “whaleback” longitudinal profile. Slight changes in that form occur with increasing size indicating predictable growth that appears to be primarily controlled by local fault geometries (i.e., bifurcation angle), rather than the influence of fault obliquity relative to far-field plate motion, due to inefficient slip-transfer across interconnected irregularly trending closely spaced faults. Modeling results indicate that the self-similar fault-bound geometry of SECSZ restraining bends may arise from elevated shear strain at the outer corners of single transpressional fault bends with increasing cumulative slip. This, in turn, promotes growth of a new fault leading to efficient accommodation of local convergent strain via uplift between bounding faults. Finally, our results indicate that the kilometer-scale restraining bends contribute minimally to regional contraction as they only penetrate the upper third of the seismogenic crust and are therefore also unlikely to impede large earthquake surface ruptures.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"50 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191799","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}
Wen-Huang Chen, Yi Yan, Andrew Carter, Peter D. Clift, Chi-Yue Huang, Graciano P. Yumul, Carla B. Dimalanta, Jillian Aira S. Gabo-Ratio, Le Zhang, Ming-Huei Wang, Xin-Chang Zhang
The evolution of arc-continent collision between the Palawan microcontinental block and the Cagayan Ridge in the southeastern margin of the South China Sea (SCS) is vital to understand how this collision correlated with seafloor spreading of the SCS. To address the evolution of arc-continent collision, we studied the biostratigraphy and provenance of syn-collisional sediments in the Isugod Basin in central-southern Palawan. Microfossil analysis indicates a Late Miocene age (11.5–5.6 Ma) for the Isugod and Alfonso XIII Formations and rapid subsidence during initiation of the basin which may have been triggered by local extensional collapse of the wedge in response to forearc uplift. Multidisciplinary provenance analysis reveals that the Isugod and Alfonso XIII Formations were derived from the Middle Eocene–lower Oligocene Panas-Pandian Formation on the Palawan wedge and the Late Eocene Central Palawan Ophiolite. These results suggest the emergence of both the orogenic wedge and obducted forearc ophiolite at ∼11.5 Ma, implying collision onset before ∼11.5 Ma. The collision initiation in Palawan could be better constrained to ∼18 Ma, based on the drowning of the Nido carbonate platform in the foreland. Therefore, the gravitational collapse of the Palawan wedge and the subsidence/formation of the Isugod Basin might reflect a significant uplift pulse in the hinterland of the wedge beginning within 13.4–11.5 Ma in the late stage of collision. It indicates that although compression originated from spreading of the SCS had ceased at 16–15 Ma, arc-continent collision in Palawan did not stop and was sustained by compression from the upper plate afterward.
巴拉望微大陆块与南中国海（SCS）东南缘卡加延海脊之间的弧-大陆碰撞演化，对于了解这种碰撞如何与南中国海的海底扩张相关至关重要。针对弧-大陆碰撞的演化，我们研究了巴拉望岛中南部伊苏戈德盆地同步碰撞沉积物的生物地层学和产状。微化石分析表明，伊苏古德和阿方索十三世地层的年代为晚中新世（11.5-5.6Ma），在盆地形成过程中出现了快速下沉，这可能是由于前弧隆升导致楔块局部伸展塌陷而引发的。多学科成因分析表明，伊苏古德地层和阿方索十三世地层源自巴拉望楔上的中始新世-下新世帕纳斯-潘迪亚地层和晚始新世巴拉望中部蛇绿岩。这些结果表明，造山楔和俯冲前弧蛇绿混杂岩都在∼11.5Ma出现，这意味着碰撞发生在∼11.5Ma之前。根据尼多碳酸盐平台在前陆的淹没情况，巴拉望岛的碰撞起始时间可以更好地确定为 ∼18 Ma。因此，巴拉望楔块的重力塌陷和伊苏古德盆地的下沉/形成可能反映了楔块腹地在碰撞晚期的13.4-11.5 Ma内开始的显著隆升脉冲。这表明，虽然源于南中国海扩张的挤压在 16-15 Ma 时已经停止，但巴拉望的弧-大陆碰撞并未停止，而是在之后由上板块的挤压维持着。
{"title":"Evolution of Arc-Continent Collision in the Southeastern Margin of the South China Sea: Insight From the Isugod Basin in Central-Southern Palawan","authors":"Wen-Huang Chen, Yi Yan, Andrew Carter, Peter D. Clift, Chi-Yue Huang, Graciano P. Yumul, Carla B. Dimalanta, Jillian Aira S. Gabo-Ratio, Le Zhang, Ming-Huei Wang, Xin-Chang Zhang","doi":"10.1029/2023tc008078","DOIUrl":"https://doi.org/10.1029/2023tc008078","url":null,"abstract":"The evolution of arc-continent collision between the Palawan microcontinental block and the Cagayan Ridge in the southeastern margin of the South China Sea (SCS) is vital to understand how this collision correlated with seafloor spreading of the SCS. To address the evolution of arc-continent collision, we studied the biostratigraphy and provenance of syn-collisional sediments in the Isugod Basin in central-southern Palawan. Microfossil analysis indicates a Late Miocene age (11.5–5.6 Ma) for the Isugod and Alfonso XIII Formations and rapid subsidence during initiation of the basin which may have been triggered by local extensional collapse of the wedge in response to forearc uplift. Multidisciplinary provenance analysis reveals that the Isugod and Alfonso XIII Formations were derived from the Middle Eocene–lower Oligocene Panas-Pandian Formation on the Palawan wedge and the Late Eocene Central Palawan Ophiolite. These results suggest the emergence of both the orogenic wedge and obducted forearc ophiolite at ∼11.5 Ma, implying collision onset before ∼11.5 Ma. The collision initiation in Palawan could be better constrained to ∼18 Ma, based on the drowning of the Nido carbonate platform in the foreland. Therefore, the gravitational collapse of the Palawan wedge and the subsidence/formation of the Isugod Basin might reflect a significant uplift pulse in the hinterland of the wedge beginning within 13.4–11.5 Ma in the late stage of collision. It indicates that although compression originated from spreading of the SCS had ceased at 16–15 Ma, arc-continent collision in Palawan did not stop and was sustained by compression from the upper plate afterward.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"36 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191771","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}
Yazhou Miao, Jian Zhang, Karel Schulmann, Alexandra Guy, Igor Soejono, Yingde Jiang, Min Sun, Shuhui Zhang, Zhiyong Li
The geodynamic evolution of the East Junggar is examined by means of satellite imaging and field-based structural studies, U-Pb zircon geochronology and analysis of potential field geophysical data in the Yemaquan arc and the Dulate back-arc systems. The northern Yemaquan arc shows a pervasive WNW–ESE steep S1 foliation that is related to the exhumation of Armantai ophiolitic mélange in an F1 antiformal structure. The bedding of the Dulate sequences is folded by N–S-trending F1 upright folds that are preserved in low strain domains. The timing of D1 is estimated between 310 and 280 Ma. During D2, previously folded Dulate sequences were orthogonally refolded by E–W-trending F2 upright folds, resulting in Type-1 basin and dome interference pattern and pervasive E–W trending S2 cleavage zones. The age of D2 is constrained to be 270–250 Ma based on the dating of syn-tectonic pegmatites and deposition of syn-orogenic sedimentary rocks. The boundary between the Yemaquan arc and Dulate back-arc basin experienced reactivation through D2 dextral transpressive shear zones. The D1 fabrics are the consequence of the closure of the Dulate back-arc basin due to the advancing mode of Kalamaili subduction. Almost orthogonal Permian D2 fabrics were generated by the N–S shortening of the East Junggar and the northward movement of the Junggar Block indenter. This D2 deformation was associated with the anticlockwise rotation of the southern limb of the Mongolian Orocline, the scissor-like closure of the northerly Mongol-Okhotsk Ocean and the collision of the Mongolian and the Tarim–North China craton collages.
通过卫星成像和野外构造研究、U-Pb锆石地质年代以及对叶马泉弧和Dulate后弧系统潜在野外地球物理数据的分析，研究了东准噶尔的地球动力演化。叶马泉弧北部显示出普遍的 WNW-ESE 陡峭 S1 褶皱，这与阿曼台蛇绿岩夹层在 F1 反形貌结构中的出露有关。Dulate序列的基底被保留在低应变域中的N-S向F1直立褶皱所褶皱。D1 的时间估计在 310 至 280 Ma 之间。在D2期间，先前褶皱的Dulate序列被东西走向的F2直立褶皱正交再褶皱，形成了1型盆地和穹隆干扰模式以及普遍的东西走向S2劈裂带。根据同步构造伟晶岩的年代测定和同步成因沉积岩的沉积，D2 的年龄被推定为 270-250 Ma。Yemaquan弧与Dulate后弧盆地之间的边界通过D2右旋转位剪切带重新激活。D1 构造是由于卡拉麦里俯冲模式的推进导致迪特后弧盆地关闭的结果。几乎正交的二叠纪 D2 构造是由东准噶尔北-南向缩短和准噶尔地块压头北移产生的。这种D2变形与蒙古鄂伦春山脉南缘的逆时针旋转、蒙古-奥霍次克洋向北的剪刀状闭合以及蒙古和塔里木-华北克拉通碰撞有关。
{"title":"Switching From Subduction Zone Advance to Retreat Explains the Late Paleozoic Evolution of the East Junggar System, Central Asian Orogenic Belt","authors":"Yazhou Miao, Jian Zhang, Karel Schulmann, Alexandra Guy, Igor Soejono, Yingde Jiang, Min Sun, Shuhui Zhang, Zhiyong Li","doi":"10.1029/2024tc008254","DOIUrl":"https://doi.org/10.1029/2024tc008254","url":null,"abstract":"The geodynamic evolution of the East Junggar is examined by means of satellite imaging and field-based structural studies, U-Pb zircon geochronology and analysis of potential field geophysical data in the Yemaquan arc and the Dulate back-arc systems. The northern Yemaquan arc shows a pervasive WNW–ESE steep S<sub>1</sub> foliation that is related to the exhumation of Armantai ophiolitic mélange in an F<sub>1</sub> antiformal structure. The bedding of the Dulate sequences is folded by N–S-trending F<sub>1</sub> upright folds that are preserved in low strain domains. The timing of D<sub>1</sub> is estimated between 310 and 280 Ma. During D<sub>2</sub>, previously folded Dulate sequences were orthogonally refolded by E–W-trending F<sub>2</sub> upright folds, resulting in Type-1 basin and dome interference pattern and pervasive E–W trending S<sub>2</sub> cleavage zones. The age of D<sub>2</sub> is constrained to be 270–250 Ma based on the dating of syn-tectonic pegmatites and deposition of syn-orogenic sedimentary rocks. The boundary between the Yemaquan arc and Dulate back-arc basin experienced reactivation through D<sub>2</sub> dextral transpressive shear zones. The D<sub>1</sub> fabrics are the consequence of the closure of the Dulate back-arc basin due to the advancing mode of Kalamaili subduction. Almost orthogonal Permian D<sub>2</sub> fabrics were generated by the N–S shortening of the East Junggar and the northward movement of the Junggar Block indenter. This D<sub>2</sub> deformation was associated with the anticlockwise rotation of the southern limb of the Mongolian Orocline, the scissor-like closure of the northerly Mongol-Okhotsk Ocean and the collision of the Mongolian and the Tarim–North China craton collages.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"36 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191797","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}
Kevin P. Furlong, Antonio Villaseñor, Harley M. Benz, Kirsty A. McKenzie
The northward migration of the Mendocino triple junction (MTJ) drives a fundamental plate boundary transformation from convergence to translation; producing a series of strike-slip faults, that become the San Andreas plate boundary. We find that the 3-D structure of the Pacific plate lithosphere in the vicinity of the MTJ controls the location of San Andreas plate boundary formation. At the time of initiation of the Pacific-North America plate boundary (∼30 Ma), the sequential interaction with the western margin of North America of the Pioneer Fracture Zone, soon followed by the Mendocino Fracture Zone, led to the capture of a small segment of partially subducted Farallon lithosphere by the Pacific plate, termed the Pioneer Fragment (PF). Since that time, the PF has translated with the Pacific Plate along the western margin of North America. Recently developed, high-resolution seismic-tomographic imagery of northern California indicates that (a) the PF is extant, occupying the western half of the slab window, immediately south of the MTJ; (b) the eastern edge of the PF lies beneath the newly forming Maacama fault system, which develops to become the locus for the primary plate boundary structure after approximately 6–10 Ma; and (c) the location of the translating PF adjacent to the asthenosphere of the slab window generates a shear zone within and below the crust that develops into the plate boundary faults. As a result, the San Andreas plate boundary forms interior to the western margin of North America, rather than at its western edge.
{"title":"Formation and Evolution of the Pacific-North American (San Andreas) Plate Boundary: Constraints From the Crustal Architecture of Northern California","authors":"Kevin P. Furlong, Antonio Villaseñor, Harley M. Benz, Kirsty A. McKenzie","doi":"10.1029/2023tc007963","DOIUrl":"https://doi.org/10.1029/2023tc007963","url":null,"abstract":"The northward migration of the Mendocino triple junction (MTJ) drives a fundamental plate boundary transformation from convergence to translation; producing a series of strike-slip faults, that become the San Andreas plate boundary. We find that the 3-D structure of the Pacific plate lithosphere in the vicinity of the MTJ controls the location of San Andreas plate boundary formation. At the time of initiation of the Pacific-North America plate boundary (∼30 Ma), the sequential interaction with the western margin of North America of the Pioneer Fracture Zone, soon followed by the Mendocino Fracture Zone, led to the capture of a small segment of partially subducted Farallon lithosphere by the Pacific plate, termed the Pioneer Fragment (PF). Since that time, the PF has translated with the Pacific Plate along the western margin of North America. Recently developed, high-resolution seismic-tomographic imagery of northern California indicates that (a) the PF is extant, occupying the western half of the slab window, immediately south of the MTJ; (b) the eastern edge of the PF lies beneath the newly forming Maacama fault system, which develops to become the locus for the primary plate boundary structure after approximately 6–10 Ma; and (c) the location of the translating PF adjacent to the asthenosphere of the slab window generates a shear zone within and below the crust that develops into the plate boundary faults. As a result, the San Andreas plate boundary forms interior to the western margin of North America, rather than at its western edge.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"50 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141191772","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. E. Martos, L. M. Fennell, M. Naipauer, V. Valencia, A. Folguera
The early stages of Andean construction have been barely recognized due to a long history of tectonic superposition during the growth of the orogen. In this work, we present a multi-method approach integrating sedimentological, geochronological, structural, and provenance analyses to reconstruct the architecture of the Late Cretaceous foreland basin at 34°40’S. We identified a new depocenter located in an inner position of the Late Cretaceous foreland basin, a strategic location to understand the sedimentation dynamics near the topographic front of the orogen. Two sandstone samples from the basal and upper sections of the Diamante Formation were collected for detrital zircons dating, which yielded maximum depositional ages between 98 Ma and 91 Ma. The provenance analyses based on U-Pb zircons ages indicated a main source area located to the west, in the incipient orogenic belt, with a complementary contribution from basement rocks, located to the east. Moreover, growth strata documented in these deposits were compared with structural kinematic models, which suggest that some of these deposits are associated with inherited structures, reactivated during the tectonic inversion of the extensional Jurassic Atuel depocenter. Our paleogeographic model comprises an Andean Cordillera flanked by a hinterland basin to the west and a foreland basin to the east, with a deformational front positioned further east compared to previous models.
由于在造山运动的发展过程中发生了长期的构造叠加，安第斯山脉的早期构造阶段几乎没有被认识到。在这项工作中，我们提出了一种综合沉积学、地质年代学、构造和产状分析的多方法方法，以重建南纬34°40'晚白垩世前陆盆地的结构。我们在晚白垩世前陆盆地的内部位置发现了一个新的沉积中心，这是了解造山带地形前沿附近沉积动力学的战略要地。研究人员从迪亚曼特地层的基底和上部采集了两个砂岩样本，进行了碎屑锆石测年，得出的最大沉积年龄在 98 Ma 到 91 Ma 之间。根据铀-铅锆石年龄进行的产地分析表明，主要来源区位于西面的初生造山带，东面的基底岩石对其有补充作用。此外，我们还将这些矿床中记录的生长地层与构造运动模型进行了比较，结果表明其中一些矿床与继承构造有关，这些构造在侏罗纪阿图尔沉积中心的伸展反转过程中被重新激活。我们的古地理模型包括一个安第斯科迪勒拉山系，西侧为腹地盆地，东侧为前陆盆地，与之前的模型相比，变形前沿位于更靠东的位置。
{"title":"The Ancient Configuration of the Southern Central Andes and Paleogeographic Reconstruction of the Late Cretaceous Foreland Basin at 34°40’S","authors":"F. E. Martos, L. M. Fennell, M. Naipauer, V. Valencia, A. Folguera","doi":"10.1029/2023tc008119","DOIUrl":"https://doi.org/10.1029/2023tc008119","url":null,"abstract":"The early stages of Andean construction have been barely recognized due to a long history of tectonic superposition during the growth of the orogen. In this work, we present a multi-method approach integrating sedimentological, geochronological, structural, and provenance analyses to reconstruct the architecture of the Late Cretaceous foreland basin at 34°40’S. We identified a new depocenter located in an inner position of the Late Cretaceous foreland basin, a strategic location to understand the sedimentation dynamics near the topographic front of the orogen. Two sandstone samples from the basal and upper sections of the Diamante Formation were collected for detrital zircons dating, which yielded maximum depositional ages between 98 Ma and 91 Ma. The provenance analyses based on U-Pb zircons ages indicated a main source area located to the west, in the incipient orogenic belt, with a complementary contribution from basement rocks, located to the east. Moreover, growth strata documented in these deposits were compared with structural kinematic models, which suggest that some of these deposits are associated with inherited structures, reactivated during the tectonic inversion of the extensional Jurassic Atuel depocenter. Our paleogeographic model comprises an Andean Cordillera flanked by a hinterland basin to the west and a foreland basin to the east, with a deformational front positioned further east compared to previous models.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"19 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141173280","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}
P. Santolaria, C. Ayala, R. Soto, P. Clariana, F. M. Rubio, J. Martín-León, E. L. Pueyo, J. A. Muñoz
Triassic evaporites represent the regional décollement of the Pyrenees and form two salt provinces north and south of the South Pyrenean Central Salient (SPCS). We present an updated Bouguer and residual Bouguer anomaly map built upon the homogenization of available gravity data of the SPCS together with four new and representative cross-sections, constrained by geological data acquired in the field, seismic, well, and gravity data (gravity forward modeling). Gravity anomaly maps and cross-sections are used to characterize the present-day uneven distribution of Triassic evaporites. Outcropping Triassic evaporites is not necessarily associated with an underlying evaporite accumulation and the absence of it at surface does not involves its non-existence at depth. Northwest of the salient, a major accumulation of Triassic evaporites floors a thick syn-orogenic Upper Cretaceous basin. South of it, Triassic rocks core salt-detached anticlines related to the Pyrenean orogeny. Along the southernmost (and youngest) thrust sheet of the salient, diapirs, and evaporite accumulations are associated with a salt-inflated area.
{"title":"Salt Distribution in the South Pyrenean Central Salient: Insights From Gravity Anomalies","authors":"P. Santolaria, C. Ayala, R. Soto, P. Clariana, F. M. Rubio, J. Martín-León, E. L. Pueyo, J. A. Muñoz","doi":"10.1029/2024tc008274","DOIUrl":"https://doi.org/10.1029/2024tc008274","url":null,"abstract":"Triassic evaporites represent the regional décollement of the Pyrenees and form two salt provinces north and south of the South Pyrenean Central Salient (SPCS). We present an updated Bouguer and residual Bouguer anomaly map built upon the homogenization of available gravity data of the SPCS together with four new and representative cross-sections, constrained by geological data acquired in the field, seismic, well, and gravity data (gravity forward modeling). Gravity anomaly maps and cross-sections are used to characterize the present-day uneven distribution of Triassic evaporites. Outcropping Triassic evaporites is not necessarily associated with an underlying evaporite accumulation and the absence of it at surface does not involves its non-existence at depth. Northwest of the salient, a major accumulation of Triassic evaporites floors a thick syn-orogenic Upper Cretaceous basin. South of it, Triassic rocks core salt-detached anticlines related to the Pyrenean orogeny. Along the southernmost (and youngest) thrust sheet of the salient, diapirs, and evaporite accumulations are associated with a salt-inflated area.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"43 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140932033","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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