Pub Date : 2024-11-01Epub Date: 2024-11-24DOI: 10.1029/2023TC008086
Manuel Diercks, Ekbal Hussain, Zoë K Mildon, Sarah J Boulton, Milan Lazecký
Quantifying interseismic deformation of fault networks which are predominantly deforming in a north-south direction is challenging, because GNSS networks are usually not dense enough to resolve deformation at the level of individual faults. The alternative, interferometric synthetic aperture radar (InSAR), provides high spatial resolution but is limited by a low sensitivity to N-S motion. We study the active normal fault network of Western Türkiye, which is undergoing rapid N-S extension, using InSAR. Since most faults in the study region are normal faults, we overcome the low N-S sensitivity by focusing on the vertical deformation component, which presents its own challenges. Sediment-filled grabens show rapid anthropogenically induced subsidence, whereas urban areas tend toward erroneous uplift signals. Additionally, the morphological relief results in topographic and atmospheric disturbances of the InSAR signal. Our solution to these challenges is a systematic analysis of the high-resolution vertical velocity field to deduce insights into regional deformation patterns, combined with detailed investigations of deformation along individual faults in the Western Anatolian Extensional Province. We show that tectonic deformation in the large graben systems is not restricted to the main faults. Smaller and seemingly less active faults are accommodating strain, favoring a continuum model of deformation over block models. We also observe a potential correlation between recent seismicity and active interseismic surface deformation. Observed deformation rates provide an estimate of current activity for many faults in the region. We discuss the potential and limitations of InSAR time series analysis for extensional regimes.
{"title":"Active Deformation Across the Western Anatolian Extensional Province (Türkiye) From Sentinel-1 InSAR.","authors":"Manuel Diercks, Ekbal Hussain, Zoë K Mildon, Sarah J Boulton, Milan Lazecký","doi":"10.1029/2023TC008086","DOIUrl":"10.1029/2023TC008086","url":null,"abstract":"<p><p>Quantifying interseismic deformation of fault networks which are predominantly deforming in a north-south direction is challenging, because GNSS networks are usually not dense enough to resolve deformation at the level of individual faults. The alternative, interferometric synthetic aperture radar (InSAR), provides high spatial resolution but is limited by a low sensitivity to N-S motion. We study the active normal fault network of Western Türkiye, which is undergoing rapid N-S extension, using InSAR. Since most faults in the study region are normal faults, we overcome the low N-S sensitivity by focusing on the vertical deformation component, which presents its own challenges. Sediment-filled grabens show rapid anthropogenically induced subsidence, whereas urban areas tend toward erroneous uplift signals. Additionally, the morphological relief results in topographic and atmospheric disturbances of the InSAR signal. Our solution to these challenges is a systematic analysis of the high-resolution vertical velocity field to deduce insights into regional deformation patterns, combined with detailed investigations of deformation along individual faults in the Western Anatolian Extensional Province. We show that tectonic deformation in the large graben systems is not restricted to the main faults. Smaller and seemingly less active faults are accommodating strain, favoring a continuum model of deformation over block models. We also observe a potential correlation between recent seismicity and active interseismic surface deformation. Observed deformation rates provide an estimate of current activity for many faults in the region. We discuss the potential and limitations of InSAR time series analysis for extensional regimes.</p>","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"43 11","pages":"e2023TC008086"},"PeriodicalIF":3.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11586515/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142732746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01Epub Date: 2024-11-21DOI: 10.1029/2024TC008412
T A Ducharme, D A Schneider, B Grasemann, V Scoging, C Bakowsky, K P Larson, A Camacho
The Almyropotamos tectonic window on southern Evia island in the NW Aegean Sea divides two high pressure-low temperature metamorphic units, representing distinct Hellenic thrust sheets. Ductile thinning along the major low-angle Evia Shear Zone has closely juxtaposed the lower (Basal Unit) marble-flysch sequence structurally below Styra marbles (Cycladic Blueschist Unit). The partially attenuated flysch comprises a matrix dominated by pelitic schist, with dispersed cm- to hm-scale blocks of marble, carbonate schist, quartzite, and metabasite. Structural investigation of the different lithotypes in the flysch reveals tectonic fabrics related to general flattening strain are developed most strongly in the pelitic matrix, whereas the compositionally diverse blocks exhibit differential preservation of older structures. Quartz c-axis distributions from quartz veins in the schists reflect an early, moderate temperature plane strain deformation. Colder deformation is evident in some pelitic schists, capturing Z-centered girdles consistent with the oblate finite strain ellipsoid inferred from macroscopic structures. New in situ 40Ar/39Ar and 87Rb/87Sr geochronology delineate the timing of the two deformation events. Geochronological data reaffirm the first-order observations of strain partitioning behavior at the scale of the shear zone, and confirm that the structure records two resolvable tectonometamorphic events: an early Oligocene HP-LT event, and a late Oligocene-early Miocene greenschist facies overprint coinciding with ductile thinning. The diffuse and discontinuous style of deformation recorded within the shear zone is unusual for major structures facilitating exhumation in the Aegean Sea, and may represent an analogue to mélange-hosted shear zones that accommodate progressive strain during subduction.
爱琴海西北部埃维亚岛南部的阿尔米罗波塔莫斯构造窗口划分出两个高压低温变质岩单元，分别代表不同的希腊推力片。沿着主要的低角度埃维亚剪切带的延展性减薄使下部（基底单元）大理岩-萤石层序在结构上紧密地并置在斯蒂拉大理岩（基克拉泽斯蓝岩单元）之下。部分衰减的萤石岩包括以辉绿岩片岩为主的基质，以及分散的厘米至百米级的大理岩、碳酸盐片岩、石英岩和偏闪长岩块。对萤石岩中不同岩型的构造调查显示，与总体扁平应变有关的构造结构在辉绿岩基质中发育得最为强烈，而成分多样的岩块则表现出对古老构造的不同保留。片岩中石英脉的石英 c 轴分布反映了早期的中温平面应变变形。在一些辉绿岩片岩中，低温变形非常明显，捕捉到了与宏观结构推断的扁圆形有限应变椭球体一致的Z中心腰带。新的原位 40Ar/39Ar 和 87Rb/87Sr 地质年代划分了两次变形事件的时间。地质年代数据再次证实了剪切带尺度上应变分区行为的一阶观测结果，并确认该构造记录了两次可解析的构造变质事件：一次是早渐新世的HP-LT事件，另一次是晚渐新世-中新世早期的绿泥石面叠加事件，与韧性变薄同时发生。在该剪切带内记录到的弥漫和不连续的变形风格，在爱琴海促进掘起的主要构造中并不常见，可能代表了在俯冲过程中容纳渐进应变的蜕变带。
{"title":"Strain Partitioning in a Flattening Shear Zone: Re-Evaluation of a Cycladic Style Detachment.","authors":"T A Ducharme, D A Schneider, B Grasemann, V Scoging, C Bakowsky, K P Larson, A Camacho","doi":"10.1029/2024TC008412","DOIUrl":"10.1029/2024TC008412","url":null,"abstract":"<p><p>The Almyropotamos tectonic window on southern Evia island in the NW Aegean Sea divides two high pressure-low temperature metamorphic units, representing distinct Hellenic thrust sheets. Ductile thinning along the major low-angle Evia Shear Zone has closely juxtaposed the lower (Basal Unit) marble-flysch sequence structurally below Styra marbles (Cycladic Blueschist Unit). The partially attenuated flysch comprises a matrix dominated by pelitic schist, with dispersed cm- to hm-scale blocks of marble, carbonate schist, quartzite, and metabasite. Structural investigation of the different lithotypes in the flysch reveals tectonic fabrics related to general flattening strain are developed most strongly in the pelitic matrix, whereas the compositionally diverse blocks exhibit differential preservation of older structures. Quartz c-axis distributions from quartz veins in the schists reflect an early, moderate temperature plane strain deformation. Colder deformation is evident in some pelitic schists, capturing Z-centered girdles consistent with the oblate finite strain ellipsoid inferred from macroscopic structures. New in situ <sup>40</sup>Ar/<sup>39</sup>Ar and <sup>87</sup>Rb/<sup>87</sup>Sr geochronology delineate the timing of the two deformation events. Geochronological data reaffirm the first-order observations of strain partitioning behavior at the scale of the shear zone, and confirm that the structure records two resolvable tectonometamorphic events: an early Oligocene HP-LT event, and a late Oligocene-early Miocene greenschist facies overprint coinciding with ductile thinning. The diffuse and discontinuous style of deformation recorded within the shear zone is unusual for major structures facilitating exhumation in the Aegean Sea, and may represent an analogue to mélange-hosted shear zones that accommodate progressive strain during subduction.</p>","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"43 11","pages":"e2024TC008412"},"PeriodicalIF":3.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11582021/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142711081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigated the diagnostic accuracy (DA) and clinical utility (CU) of DNA methylation (5 methylcytosine) in occupational Pb-exposure from Pb based industry. Blood Lead levels (BLLs) were measured using the ICP-OES method. The total DNA methylation (5-mC) was quantified using ELISA method. Based on their BLLs, the Pb-exposed workers were categorised into three groups: low (< 10 µg/dL), moderate (10-30 µg/dL), and high exposure (> 30 µg/dL). DNA methylation (5-mC) was significantly lower in moderate and high Pb-exposure groups when compared to the low Pb-exposure group. Workers exposed to high levels of Pb-exposure, the DA variables of 5-mC showed that the sensitivity was 74.7% [95% CI 65.4-84.0], specificity was 69.6% [95% CI 50.8-88.4], positive predictive value (PPV) was 89.9% [95% CI 82.7-97.0], Postive likelihood ratio (LR+) was 2.454 [95% CI 1.3-4.6], and diagnostic odds ratio (DOR) is 6.3 [95% CI 6.5-7.7]. In moderate Pb-exposure, the DA variables of 5-mC revealed that the sensitivity is 64.9% [95% CI 55.2-74.5], the specificity is 69.6% [95% CI 50.8-88.4], the PPV is 89.7% [95% CI 82.5-97.0], the LR+ is 2.132 [95% CI 1.13-4.03], and the DOR is 4.2 [95% CI 3.6-5.7]. The high Pb-exposure group had higher DA metrics when compared to moderate Pb exposure. The clinical utility (CU+) of 5-mC was found to have good utility of 0.671 [95% CI 0.566-0.776] in the high Pb exposure group and fair utility of 0.582 [95% CI 0.470-0.694] in moderate Pb exposure group. In conclusion, DNA methylation (5mC) could be used as a predictive biomarker for high Pb-exposure.
本研究调查了 DNA 甲基化（5 甲基胞嘧啶）在铅工业职业性铅暴露中的诊断准确性（DA）和临床实用性（CU）。采用 ICP-OES 方法测量血液铅含量 (BLL)。DNA 总甲基化（5-mC）采用 ELISA 方法进行量化。根据他们的血铅含量，受铅污染的工人被分为三组：低（30 µg/dL）组、中（30 µg/dL）组和高（30 µg/dL）组。与低铅暴露组相比，中度和高度铅暴露组的 DNA 甲基化（5-mC）明显较低。在暴露于高浓度铅的工人中，5-mC 的 DA 变量显示灵敏度为 74.7% [95% CI 65.4-84.0]，特异性为 69.6% [95% CI 50.8-88.4]，阳性预测值（positive predictive value，阳性预测值）为 0.5%。阳性预测值（PPV）为 89.9% [95% CI 82.7-97.0]，阳性似然比（LR+）为 2.454 [95% CI 1.3-4.6]，诊断几率比（DOR）为 6.3 [95% CI 6.5-7.7]。在中度铅暴露中，5-mC 的 DA 变量显示灵敏度为 64.9% [95% CI 55.2-74.5]，特异性为 69.6% [95% CI 50.8-88.4]，PPV 为 89.7% [95% CI 82.5-97.0]，LR+ 为 2.132 [95% CI 1.13-4.03]，DOR 为 4.2 [95% CI 3.6-5.7]。与中度铅暴露相比，高铅暴露组的 DA 指标更高。在高铅暴露组，5-mC 的临床实用性（CU+）为 0.671 [95% CI 0.566-0.776]，良好；在中度铅暴露组，5-mC 的临床实用性为 0.582 [95% CI 0.470-0.694]，一般。总之，DNA甲基化（5mC）可作为高铅暴露的预测性生物标志物。
{"title":"Assessment of Diagnostic Accuracy and Clinical Utility of DNA Methylation (5-mC) in Detecting Severity of Occupational Lead Exposure.","authors":"Ravibabu Kalahasthi, Vinay Kumar Adepu, Raju Nagaraju","doi":"10.1007/s12291-023-01138-z","DOIUrl":"10.1007/s12291-023-01138-z","url":null,"abstract":"<p><p>This study investigated the diagnostic accuracy (DA) and clinical utility (CU) of DNA methylation (5 methylcytosine) in occupational Pb-exposure from Pb based industry. Blood Lead levels (BLLs) were measured using the ICP-OES method. The total DNA methylation (5-mC) was quantified using ELISA method. Based on their BLLs, the Pb-exposed workers were categorised into three groups: low (< 10 µg/dL), moderate (10-30 µg/dL), and high exposure (> 30 µg/dL). DNA methylation (5-mC) was significantly lower in moderate and high Pb-exposure groups when compared to the low Pb-exposure group. Workers exposed to high levels of Pb-exposure, the DA variables of 5-mC showed that the sensitivity was 74.7% [95% CI 65.4-84.0], specificity was 69.6% [95% CI 50.8-88.4], positive predictive value (PPV) was 89.9% [95% CI 82.7-97.0], Postive likelihood ratio (LR+) was 2.454 [95% CI 1.3-4.6], and diagnostic odds ratio (DOR) is 6.3 [95% CI 6.5-7.7]. In moderate Pb-exposure, the DA variables of 5-mC revealed that the sensitivity is 64.9% [95% CI 55.2-74.5], the specificity is 69.6% [95% CI 50.8-88.4], the PPV is 89.7% [95% CI 82.5-97.0], the LR+ is 2.132 [95% CI 1.13-4.03], and the DOR is 4.2 [95% CI 3.6-5.7]. The high Pb-exposure group had higher DA metrics when compared to moderate Pb exposure. The clinical utility (CU+) of 5-mC was found to have good utility of 0.671 [95% CI 0.566-0.776] in the high Pb exposure group and fair utility of 0.582 [95% CI 0.470-0.694] in moderate Pb exposure group. In conclusion, DNA methylation (5mC) could be used as a predictive biomarker for high Pb-exposure.</p>","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"12 1","pages":"572-578"},"PeriodicalIF":1.5,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11436711/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79273717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eben B. Hodgin, Nicholas L. Swanson-Hysell, Andrew R. C. Kylander-Clark, Andrew C. Turner, Daniel A. Stolper, Daniel E. Ibarra, Mark D. Schmitz, Yiming Zhang, Luke M. Fairchild, Anthony J. Fuentes
The North American craton interior preserves a >1 Ga history of near surface processes that inform ongoing debates regarding timing and drivers of continental-scale deformation and erosion associated with far-field orogenesis. We tested various models of structural inversion on a major segment of the Midcontinent Rift along the Douglas Fault (DF) in northern Wisconsin, which accommodated ≳10 km of total vertical displacement. U-Pb detrital zircon and vein calcite Δ47/U-Pb thermochronometry from the hanging wall constrain the majority of uplift (≳8.5 km) and deformation to 1052–1036 Ma during the Ottawan phase of the Grenvillian orogeny. Combined U-Pb zircon dates, Δ47/U-Pb calcite thermochronometry, and field data that document syn- to early post-depositional deformation in the footwall constrain a second stage of uplift (1–1.5 km) ca. 995–980 Ma during the Rigolet phase of the Grenvillian orogeny. A minor phase of Appalachian far-field orogenesis is associated with minimal thrust reactivation. Our combined analyses identified the 995–980 Ma Bayfield Group as a Grenvillian foreland basin with an original thickness 0.5–2 km greater than currently preserved. By quantifying flexural loading and other subsidence mechanisms along the Douglas Fault, we identify dynamic subsidence as a mechanism that could be consistent with the development of late-Grenvillian transcontinental fluvial systems. Minimal post-Grenvillian erosion (0.5–2 km) in this part of the craton interior has preserved the Bayfield Group and equivalent successions, limiting the magnitude of regional erosion that can be attributed to Neoproterozoic glaciation.
北美克拉通内部保留了近地表过程的 1 Ga 历史，为目前关于与远场造山运动相关的大陆尺度变形和侵蚀的时间和驱动因素的争论提供了信息。我们在威斯康星州北部沿道格拉斯断层（DF）的中大陆裂谷的一个主要地段测试了各种结构反演模型，该地段的总垂直位移达≳10 km。来自悬壁的U-Pb锆石和矿脉方解石Δ47/U-Pb热年代测定法将大部分隆起（≳8.5千米）和变形推定为格伦维利造山运动奥塔旺阶段的1052-1036Ma。综合U-Pb锆石日期、Δ47/U-Pb方解石热时序测定法以及记录了脚壁同步变形到沉积后早期变形的野外数据，可以推断出在格勒维利造山运动的里戈莱特阶段，大约在995-980 Ma发生了第二阶段的隆起（1-1.5 km）。阿巴拉契亚远场造山运动的一个小阶段与最小的推力重新激活有关。我们的综合分析表明，995-980 Ma 贝菲尔德组是格勒维利期的前陆盆地，其原始厚度比目前保存的厚度大 0.5-2 km。通过量化道格拉斯断层沿线的挠曲荷载和其他沉降机制，我们发现动态沉降机制可能与晚格伦维利期跨洲河流系统的发展相一致。在克拉通内部的这一部分，格伦维利期后的侵蚀（0.5-2 千米）极小，保留了贝菲尔德组和等同的演替，从而限制了可归因于新近纪冰川作用的区域侵蚀程度。
{"title":"One Billion Years of Stability in the North American Midcontinent Following Two-Stage Grenvillian Structural Inversion","authors":"Eben B. Hodgin, Nicholas L. Swanson-Hysell, Andrew R. C. Kylander-Clark, Andrew C. Turner, Daniel A. Stolper, Daniel E. Ibarra, Mark D. Schmitz, Yiming Zhang, Luke M. Fairchild, Anthony J. Fuentes","doi":"10.1029/2024tc008415","DOIUrl":"https://doi.org/10.1029/2024tc008415","url":null,"abstract":"The North American craton interior preserves a >1 Ga history of near surface processes that inform ongoing debates regarding timing and drivers of continental-scale deformation and erosion associated with far-field orogenesis. We tested various models of structural inversion on a major segment of the Midcontinent Rift along the Douglas Fault (DF) in northern Wisconsin, which accommodated ≳10 km of total vertical displacement. U-Pb detrital zircon and vein calcite Δ<sub>47</sub>/U-Pb thermochronometry from the hanging wall constrain the majority of uplift (≳8.5 km) and deformation to 1052–1036 Ma during the Ottawan phase of the Grenvillian orogeny. Combined U-Pb zircon dates, Δ<sub>47</sub>/U-Pb calcite thermochronometry, and field data that document syn- to early post-depositional deformation in the footwall constrain a second stage of uplift (1–1.5 km) ca. 995–980 Ma during the Rigolet phase of the Grenvillian orogeny. A minor phase of Appalachian far-field orogenesis is associated with minimal thrust reactivation. Our combined analyses identified the 995–980 Ma Bayfield Group as a Grenvillian foreland basin with an original thickness 0.5–2 km greater than currently preserved. By quantifying flexural loading and other subsidence mechanisms along the Douglas Fault, we identify dynamic subsidence as a mechanism that could be consistent with the development of late-Grenvillian transcontinental fluvial systems. Minimal post-Grenvillian erosion (0.5–2 km) in this part of the craton interior has preserved the Bayfield Group and equivalent successions, limiting the magnitude of regional erosion that can be attributed to Neoproterozoic glaciation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"19 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259897","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}
Nolan R. Blackford, Sean P. Long, Jeffrey Lee, Kyle P. Larson, Gareth Seward, Julia L. Stevens, Hadeel Al Harthi
Documenting the magnitude of finite strain within ductile shear zones is critical for understanding lithospheric deformation. However, pervasive recrystallization within shear zones often destroys the deformed markers from which strain can be measured. Intensity parameters calculated from quartz crystallographic preferred orientation (CPO) distributions have been interpreted as proxies for the relative strain magnitude within shear zones, but thus far have not been calibrated to absolute strain magnitude. Here, we present equations that quantify the relationship between CPO intensity parameters (cylindricity and density norm) and finite strain magnitude, which we calculate by integrating quartz CPO analyses (n = 87) with strain ellipsoids from stretched detrital quartz clasts (n = 49) and macro-scale ductile thinning measurements (n = 7) from the footwall of the Northern Snake Range décollement (NSRD) in Nevada. The NSRD footwall exhibits a strain gradient, with Rs(XZ) values increasing from 5.4 ± 1.4 to 282 ± 122 eastward across the range. Cylindricity increases from 0.52 to 0.83 as Rs increases from 5.4 to 23.5, and increases gradually to 0.92 at Rs values between 160 and 404. Density norm increases from 1.68 to 2.97 as Rs increases from 5.4 to 23.5, but stays approximately constant until Rs values between 160 and 404. We present equations that express average finite strain as a function of average cylindricity and density norm, which provide a broadly applicable tool for estimating the first-order finite strain magnitude within any shear zone from which quartz CPO intensity can be measured. To demonstrate their utility, we apply our equations to published data from Himalayan shear zones and a Cordilleran core complex.
{"title":"Relating Quartz Crystallographic Preferred Orientation Intensity to Finite Strain Magnitude in the Northern Snake Range Metamorphic Core Complex, Nevada: A New Tool for Characterizing Strain Patterns in Ductilely Sheared Rocks","authors":"Nolan R. Blackford, Sean P. Long, Jeffrey Lee, Kyle P. Larson, Gareth Seward, Julia L. Stevens, Hadeel Al Harthi","doi":"10.1029/2023tc008166","DOIUrl":"https://doi.org/10.1029/2023tc008166","url":null,"abstract":"Documenting the magnitude of finite strain within ductile shear zones is critical for understanding lithospheric deformation. However, pervasive recrystallization within shear zones often destroys the deformed markers from which strain can be measured. Intensity parameters calculated from quartz crystallographic preferred orientation (CPO) distributions have been interpreted as proxies for the relative strain magnitude within shear zones, but thus far have not been calibrated to absolute strain magnitude. Here, we present equations that quantify the relationship between CPO intensity parameters (cylindricity and density norm) and finite strain magnitude, which we calculate by integrating quartz CPO analyses (<i>n</i> = 87) with strain ellipsoids from stretched detrital quartz clasts (<i>n</i> = 49) and macro-scale ductile thinning measurements (<i>n</i> = 7) from the footwall of the Northern Snake Range décollement (NSRD) in Nevada. The NSRD footwall exhibits a strain gradient, with Rs<sub>(XZ)</sub> values increasing from 5.4 ± 1.4 to 282 ± 122 eastward across the range. Cylindricity increases from 0.52 to 0.83 as Rs increases from 5.4 to 23.5, and increases gradually to 0.92 at Rs values between 160 and 404. Density norm increases from 1.68 to 2.97 as Rs increases from 5.4 to 23.5, but stays approximately constant until Rs values between 160 and 404. We present equations that express average finite strain as a function of average cylindricity and density norm, which provide a broadly applicable tool for estimating the first-order finite strain magnitude within any shear zone from which quartz CPO intensity can be measured. To demonstrate their utility, we apply our equations to published data from Himalayan shear zones and a Cordilleran core complex.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"19 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259899","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}
Chao Li, Zhongbao Zhao, Marie-Luce Chevalier, Yong Zheng, Dongliang Liu, Haijian Lu, Paul D. Bons, Haibing Li
The tectonic and topographic evolution of the southeastern Tibetan Plateau based on low-temperature thermochronology data is controversial, especially whether it is tectonically- or climatically-controlled, especially along the Lancang fault (LCF) that links the flat central plateau to the west with the high relief southeastern Tibetan Plateau to the east. To explore the tectonic evolution of the LCF and its role in the tectonic and topographic evolution of the southeastern Tibetan Plateau, we carried out detailed field investigation and low-temperature thermochronology (AHe, AFT, and ZHe) analyses. Field evidence indicate that the northern LCF splits into two branches, the Yangda-Yaxu and Baqing-Leiwuqi faults, the latter striking N50°W and dipping to the SW at ∼55°, exposing >100 m-wide fault rocks composed of a fault damage zone, breccia, and gouge. New thermochronology data and thermo-kinematic modeling results suggest rapid exhumation of the region located between these two fault branches during ∼22–10 Ma at an exhumation rate of ∼1.57 km/Ma, compared to slow cooling prior to 22 Ma and since 10 Ma. We propose that internal anti-clockwise block rotation triggered rapid local exhumation, and that the final merging of different parts of the LCF during the Early-Middle Miocene assisted the southeastward escape of Sundaland, which profoundly affected the evolution of the regional geomorphology.
{"title":"Lancang Fault Assists Block Extrusion in Southeastern Tibet During Early-Middle Miocene","authors":"Chao Li, Zhongbao Zhao, Marie-Luce Chevalier, Yong Zheng, Dongliang Liu, Haijian Lu, Paul D. Bons, Haibing Li","doi":"10.1029/2024tc008341","DOIUrl":"https://doi.org/10.1029/2024tc008341","url":null,"abstract":"The tectonic and topographic evolution of the southeastern Tibetan Plateau based on low-temperature thermochronology data is controversial, especially whether it is tectonically- or climatically-controlled, especially along the Lancang fault (LCF) that links the flat central plateau to the west with the high relief southeastern Tibetan Plateau to the east. To explore the tectonic evolution of the LCF and its role in the tectonic and topographic evolution of the southeastern Tibetan Plateau, we carried out detailed field investigation and low-temperature thermochronology (AHe, AFT, and ZHe) analyses. Field evidence indicate that the northern LCF splits into two branches, the Yangda-Yaxu and Baqing-Leiwuqi faults, the latter striking N50°W and dipping to the SW at ∼55°, exposing >100 m-wide fault rocks composed of a fault damage zone, breccia, and gouge. New thermochronology data and thermo-kinematic modeling results suggest rapid exhumation of the region located between these two fault branches during ∼22–10 Ma at an exhumation rate of ∼1.57 km/Ma, compared to slow cooling prior to 22 Ma and since 10 Ma. We propose that internal anti-clockwise block rotation triggered rapid local exhumation, and that the final merging of different parts of the LCF during the Early-Middle Miocene assisted the southeastward escape of Sundaland, which profoundly affected the evolution of the regional geomorphology.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"46 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209519","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}
M. Patyniak, A. Landgraf, A. Dzhumabaeva, S. Baikulov, A. M. Williams, F. Preusser, K. E. Abdrakhmatov, J R. Arrowsmith, M. R. Strecker
This study investigates the intricate relationship between earthquake sources and seismogenic surface ruptures in a complex tectonic setting with active faults in the continental collision zone between the southern Tien Shan and the northern Pamir Mountains in Central Asia. The study focuses on the 2008 Mw 6.6 Nura earthquake along the Pamir Frontal Thrust, where the seismogenic surface rupture occurred unexpectedly within the footwall and 10 km away from the source thrust fault. This discrepancy raises questions about the interactions and potential trigger mechanisms between tectonic structures during earthquake rupture. Using unmanned aerial vehicle photography and field inspection, our investigation integrates detailed fault-zone mapping with tectono-geomorphic observations to unravel potential interactions between subsurface structures and surface-deformation phenomena. Our findings suggest that a combination of slip along deep-seated basement faults and remotely triggered flexural slip within folded Paleogene strata led to surface rupture of overlying Quaternary glacial deposits. Geomorphological and geochronological analyses coupled with systematic displacement measurements furthermore reveal evidence of similar past ruptures within the regional fault system, suggesting a recurrence interval of 1.7 kyr and a Holocene vertical offset rate of 0.4 mm/yr. The analysis of the Nura rupture zone contributes significantly to evaluate linkages between surface and subsurface structures regarding fault-zone behavior and seismic hazard assessments. Importantly, our results highlight the critical role of on-site investigations in regions with poorly defined surface ruptures, where misinterpretation may lead to the underestimation of the impact of seismic events and limitations in assessing earthquake history and strain accumulation.
{"title":"Surface Rupture of the 2008 Mw 6.6 Nura Earthquake: Triggered Flexural-Slip Faulting in the Pamir-Tien Shan Collision Zone","authors":"M. Patyniak, A. Landgraf, A. Dzhumabaeva, S. Baikulov, A. M. Williams, F. Preusser, K. E. Abdrakhmatov, J R. Arrowsmith, M. R. Strecker","doi":"10.1029/2024tc008360","DOIUrl":"https://doi.org/10.1029/2024tc008360","url":null,"abstract":"This study investigates the intricate relationship between earthquake sources and seismogenic surface ruptures in a complex tectonic setting with active faults in the continental collision zone between the southern Tien Shan and the northern Pamir Mountains in Central Asia. The study focuses on the 2008 <i>M</i><sub>w</sub> 6.6 Nura earthquake along the Pamir Frontal Thrust, where the seismogenic surface rupture occurred unexpectedly within the footwall and 10 km away from the source thrust fault. This discrepancy raises questions about the interactions and potential trigger mechanisms between tectonic structures during earthquake rupture. Using unmanned aerial vehicle photography and field inspection, our investigation integrates detailed fault-zone mapping with tectono-geomorphic observations to unravel potential interactions between subsurface structures and surface-deformation phenomena. Our findings suggest that a combination of slip along deep-seated basement faults and remotely triggered flexural slip within folded Paleogene strata led to surface rupture of overlying Quaternary glacial deposits. Geomorphological and geochronological analyses coupled with systematic displacement measurements furthermore reveal evidence of similar past ruptures within the regional fault system, suggesting a recurrence interval of 1.7 kyr and a Holocene vertical offset rate of 0.4 mm/yr. The analysis of the Nura rupture zone contributes significantly to evaluate linkages between surface and subsurface structures regarding fault-zone behavior and seismic hazard assessments. Importantly, our results highlight the critical role of on-site investigations in regions with poorly defined surface ruptures, where misinterpretation may lead to the underestimation of the impact of seismic events and limitations in assessing earthquake history and strain accumulation.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"58 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209527","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}
Close to its southern end where it connects to the Red Sea rift, the Dead Sea strike-slip fault (DSF) becomes trans-tensional in the Gulf of Aqaba. Details of this transition, however, remain difficult to unravel as most of the active tectonic structures are located off-shore. This study focuses on uplifted marine terraces located in the Gulf of Aqaba and on Tiran Island. Using high-resolution tri-stereo Pleiades satellite imagery, we build a Digital Surface Model (DSM) at a 0.5-m resolution of the eastern coast of the gulf and Tiran Island to map 19 levels of marine terraces. The terraces are preserved at elevations from 1 m to almost 500 m above the current sea level. Correlating laterally U-Th ages obtained along the gulf with the lower levels found on Tiran Island, we build an age model to estimate the ages of the upper terraces on the island. Combining this with the terrace heights from our DSM, we derive the uplift rate affecting the terraces. The geographic extent of the terraces along the gulf suggests that the DSF is responsible for uplift along the entire eastern coastline of the gulf at a rate of about 0.14 ± 0.03 mm/year at least over the Quaternary. The uplift rate of Tiran Island, located closer to the Red Sea rift, is faster at 0.21 ± 0.02 mm/year over the past 2.4 Myr. This faster uplift rate suggests a combined tectonic uplift related to both the Dead Sea strike-slip fault system and the Red Sea rift.
{"title":"Vertical Deformation Along a Strike-Slip Plate Boundary: The Uplifted Marine Terraces of the Gulf of Aqaba and Tiran Island, at the Southern End of the Dead Sea Fault","authors":"Matthieu Ribot, Marthe Lefèvre, Yann Klinger, Edwige Pons-Branchu, Arnaud Dapoigny, Sigurjón Jónsson","doi":"10.1029/2023tc007977","DOIUrl":"https://doi.org/10.1029/2023tc007977","url":null,"abstract":"Close to its southern end where it connects to the Red Sea rift, the Dead Sea strike-slip fault (DSF) becomes trans-tensional in the Gulf of Aqaba. Details of this transition, however, remain difficult to unravel as most of the active tectonic structures are located off-shore. This study focuses on uplifted marine terraces located in the Gulf of Aqaba and on Tiran Island. Using high-resolution tri-stereo Pleiades satellite imagery, we build a Digital Surface Model (DSM) at a 0.5-m resolution of the eastern coast of the gulf and Tiran Island to map 19 levels of marine terraces. The terraces are preserved at elevations from 1 m to almost 500 m above the current sea level. Correlating laterally U-Th ages obtained along the gulf with the lower levels found on Tiran Island, we build an age model to estimate the ages of the upper terraces on the island. Combining this with the terrace heights from our DSM, we derive the uplift rate affecting the terraces. The geographic extent of the terraces along the gulf suggests that the DSF is responsible for uplift along the entire eastern coastline of the gulf at a rate of about 0.14 ± 0.03 mm/year at least over the Quaternary. The uplift rate of Tiran Island, located closer to the Red Sea rift, is faster at 0.21 ± 0.02 mm/year over the past 2.4 Myr. This faster uplift rate suggests a combined tectonic uplift related to both the Dead Sea strike-slip fault system and the Red Sea rift.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"47 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209523","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}
Shihao Hao, Lianfu Mei, Jinyun Zheng, César R. Ranero
The 2D rifting modes interpreted in traditional “magma-poor” and “magma-rich” margins cannot explain the crustal structure and inferred rifting processes in the northern South China Sea (SCS) rifted margin. The “intermediate-type” terminology has been therefore applied to the mid-northern SCS, where a “wide-rift” model has been widely accepted. However, the tectono-magmatic processes of the SCS are still debated and at least five contrasting models exist. We present a compilation of 3-D seismic volumes and regional 2-D seismic surveys covering the entire Baiyun and Liwan Sub-basins to investigate their tectonic structure and faulting style in this “wide-rift” region. We interpret two segments with contrasting tectonic styles separated by a volcanic lineament and steep transfer faults. The Baiyun Sub-basin was controlled by a landward-dipping detachment system. The Liwan Sub-basin, however, was formed by a ∼100 km-long oceanward-dipping, concave-up detachment fault working at a low angle of <10°. The lateral boundaries of the detachment system were mechanically decoupled from surrounding tectonics by a volcanic lineament/transfer zone to the west and a > 190 km-long N-S-trending left-lateral strike-slip fault to the east. The planar low-angle detachment does not resemble classical metamorphic core complex domes interpreted previously. Our results indicate a 60-80 km-wavelength segmentation within a single “wide-rift” system, indicating complex 3D rifting during crustal extension. This study supports that the intermediate SCS margin had a kinematically complex deformation style locally dominated by the interaction between detachment and transfer fault systems that might be yet unrecognized in other margins.
{"title":"Detachment and Transfer Fault Systems in the Northern South China Sea, Insights Into 3D Tectonic Segmentation of Rifted Margins","authors":"Shihao Hao, Lianfu Mei, Jinyun Zheng, César R. Ranero","doi":"10.1029/2023tc008172","DOIUrl":"https://doi.org/10.1029/2023tc008172","url":null,"abstract":"The 2D rifting modes interpreted in traditional “magma-poor” and “magma-rich” margins cannot explain the crustal structure and inferred rifting processes in the northern South China Sea (SCS) rifted margin. The “intermediate-type” terminology has been therefore applied to the mid-northern SCS, where a “wide-rift” model has been widely accepted. However, the tectono-magmatic processes of the SCS are still debated and at least five contrasting models exist. We present a compilation of 3-D seismic volumes and regional 2-D seismic surveys covering the entire Baiyun and Liwan Sub-basins to investigate their tectonic structure and faulting style in this “wide-rift” region. We interpret two segments with contrasting tectonic styles separated by a volcanic lineament and steep transfer faults. The Baiyun Sub-basin was controlled by a landward-dipping detachment system. The Liwan Sub-basin, however, was formed by a ∼100 km-long oceanward-dipping, concave-up detachment fault working at a low angle of <10°. The lateral boundaries of the detachment system were mechanically decoupled from surrounding tectonics by a volcanic lineament/transfer zone to the west and <i>a</i> > 190 km-long N-S-trending left-lateral strike-slip fault to the east. The planar low-angle detachment does not resemble classical metamorphic core complex domes interpreted previously. Our results indicate a 60-80 km-wavelength segmentation within a single “wide-rift” system, indicating complex 3D rifting during crustal extension. This study supports that the intermediate SCS margin had a kinematically complex deformation style locally dominated by the interaction between detachment and transfer fault systems that might be yet unrecognized in other margins.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"42 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209398","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}
D. C. E. Llamas, B. J. Marfito, R. Dela Cruz, M. A. Aurelio
On 18 August 2020, Masbate Island was struck by a magnitude (MW) 6.6 earthquake. This seismic event represents the second occurrence of a strong earthquake (M > 6) in 17 years, emphasizing the necessity for further investigation into the characteristics of this event. In this study, we employ Interferometric Synthetic Aperture Radar, seismicity analysis, and field investigations to comprehensively characterize the coseismic and postseismic slip associated with the event. Our findings reveal a 50-km-long fault rupture along the Masbate segment of the Philippine Fault, with ∼23 km surface rupture mapped onshore, despite the occurrence of interseismic creep. The slip distribution demonstrates decreasing displacements northwestward toward the creeping section, with a maximum left-lateral displacement of 0.97 m near the epicenter. Toward the southeast offshore, the rupture terminates at a left stepover of a fault. While the surface rupture appears relatively straight and narrowly concentrated, the secondary ruptures and mapped offshore faults reveal a more complex transtensional fault structure in the southeastern part of Masbate Island. This fault complexity represents an asperity that facilitates high-stress accumulation and rupture initiation. Postseismic slip persists for several months along the onshore creeping segment. Based on comprehensive measurements of both cumulative and coseismic slip along the Masbate fault segment, we calculate a slip rate ranging between 2.8 and 3.8 cm/year and a recurrence interval of 16–41 years for earthquakes similar to the 2020 earthquake. Our study highlights how heterogeneity in fault properties, including geometry and coupling state, influences the distribution of slip and magnitude of earthquakes. The 2020 Masbate earthquake provides valuable insights into the rupture dynamics and fault behavior of the Philippine Fault in the Masbate region.
{"title":"Surface Rupture and Fault Characteristics Associated With the 2020 Magnitude (MW) 6.6 Masbate Earthquake, Masbate Island, Philippines","authors":"D. C. E. Llamas, B. J. Marfito, R. Dela Cruz, M. A. Aurelio","doi":"10.1029/2023tc008106","DOIUrl":"https://doi.org/10.1029/2023tc008106","url":null,"abstract":"On 18 August 2020, Masbate Island was struck by a magnitude (<i>M</i><sub><i>W</i></sub>) 6.6 earthquake. This seismic event represents the second occurrence of a strong earthquake (<i>M</i> > 6) in 17 years, emphasizing the necessity for further investigation into the characteristics of this event. In this study, we employ Interferometric Synthetic Aperture Radar, seismicity analysis, and field investigations to comprehensively characterize the coseismic and postseismic slip associated with the event. Our findings reveal a 50-km-long fault rupture along the Masbate segment of the Philippine Fault, with ∼23 km surface rupture mapped onshore, despite the occurrence of interseismic creep. The slip distribution demonstrates decreasing displacements northwestward toward the creeping section, with a maximum left-lateral displacement of 0.97 m near the epicenter. Toward the southeast offshore, the rupture terminates at a left stepover of a fault. While the surface rupture appears relatively straight and narrowly concentrated, the secondary ruptures and mapped offshore faults reveal a more complex transtensional fault structure in the southeastern part of Masbate Island. This fault complexity represents an asperity that facilitates high-stress accumulation and rupture initiation. Postseismic slip persists for several months along the onshore creeping segment. Based on comprehensive measurements of both cumulative and coseismic slip along the Masbate fault segment, we calculate a slip rate ranging between 2.8 and 3.8 cm/year and a recurrence interval of 16–41 years for earthquakes similar to the 2020 earthquake. Our study highlights how heterogeneity in fault properties, including geometry and coupling state, influences the distribution of slip and magnitude of earthquakes. The 2020 Masbate earthquake provides valuable insights into the rupture dynamics and fault behavior of the Philippine Fault in the Masbate region.","PeriodicalId":22351,"journal":{"name":"Tectonics","volume":"55 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142209400","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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