{"title":"褶皱河流阶地的 21Ne 和 10Be 测定:对中国新疆昆仑山西麓古曼褶皱活动变形的约束","authors":"","doi":"10.1016/j.jsg.2024.105244","DOIUrl":null,"url":null,"abstract":"<div><p>Characterizing the active deformation of the foreland is particularly valuable for understanding the dynamics of regional structural evolution within active contractional orogens. We focus on the Guman fold, one of the most prominent fold-and-thrust belts along the foothill of the Western Kunlun Mountains (Xinjiang, China). The anticline growing above the blind thrust faults progressively deforms river terraces. However, contemporaneous terrace surfaces are buried under young deposits north of the fold. We propose a novel method that extends terrace surfaces above the forelimb of the fold within the extent of deformation determined on the seismic reflection profile, to estimate the sediment thickness after abandonment of the terraces. Furthermore, cosmogenic nuclide (<sup>10</sup>Be and <sup>21</sup>Ne) depth profile dating was used to determine the exposure ages of the two terrace surfaces: 413–673 kyr for T1b and 3.7–5.2 Myr for T3b. Combining the age and deformation amount, the slip rate on the frontal fault ramp within the fold is estimated to be 0.4<sup>+0.2</sup>/<sub>-0.1</sub> mm/yr and 0.17<sup>+0.07</sup>/<sub>-0.03</sub> mm/yr since the abandonment of the T1b and the T3b terrace respectively. These rates represent the recent crustal shortening rate across the Guman fold and likely account for most of the total crustal shortening rate across the Western Kunlun Mountains. However, these rates appear to be notably lower by an order of magnitude compared to the long-term (∼23 Ma) average crustal shortening rate (∼1.1–2.6 mm/yr) in this region. This may indicate a rapid slowing down of the deformation at the scale of the whole Western Kunlun Mountains, possibly related to a regional reorganization.</p></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"21Ne and 10Be dating of folded fluvial terraces: Constraining active deformation of the Guman fold along the foothill of the western Kunlun mountains (Xinjiang, China)\",\"authors\":\"\",\"doi\":\"10.1016/j.jsg.2024.105244\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Characterizing the active deformation of the foreland is particularly valuable for understanding the dynamics of regional structural evolution within active contractional orogens. We focus on the Guman fold, one of the most prominent fold-and-thrust belts along the foothill of the Western Kunlun Mountains (Xinjiang, China). The anticline growing above the blind thrust faults progressively deforms river terraces. However, contemporaneous terrace surfaces are buried under young deposits north of the fold. We propose a novel method that extends terrace surfaces above the forelimb of the fold within the extent of deformation determined on the seismic reflection profile, to estimate the sediment thickness after abandonment of the terraces. Furthermore, cosmogenic nuclide (<sup>10</sup>Be and <sup>21</sup>Ne) depth profile dating was used to determine the exposure ages of the two terrace surfaces: 413–673 kyr for T1b and 3.7–5.2 Myr for T3b. Combining the age and deformation amount, the slip rate on the frontal fault ramp within the fold is estimated to be 0.4<sup>+0.2</sup>/<sub>-0.1</sub> mm/yr and 0.17<sup>+0.07</sup>/<sub>-0.03</sub> mm/yr since the abandonment of the T1b and the T3b terrace respectively. These rates represent the recent crustal shortening rate across the Guman fold and likely account for most of the total crustal shortening rate across the Western Kunlun Mountains. However, these rates appear to be notably lower by an order of magnitude compared to the long-term (∼23 Ma) average crustal shortening rate (∼1.1–2.6 mm/yr) in this region. This may indicate a rapid slowing down of the deformation at the scale of the whole Western Kunlun Mountains, possibly related to a regional reorganization.</p></div>\",\"PeriodicalId\":50035,\"journal\":{\"name\":\"Journal of Structural Geology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.6000,\"publicationDate\":\"2024-08-28\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Structural Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0191814124001962\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Structural Geology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0191814124001962","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
21Ne and 10Be dating of folded fluvial terraces: Constraining active deformation of the Guman fold along the foothill of the western Kunlun mountains (Xinjiang, China)
Characterizing the active deformation of the foreland is particularly valuable for understanding the dynamics of regional structural evolution within active contractional orogens. We focus on the Guman fold, one of the most prominent fold-and-thrust belts along the foothill of the Western Kunlun Mountains (Xinjiang, China). The anticline growing above the blind thrust faults progressively deforms river terraces. However, contemporaneous terrace surfaces are buried under young deposits north of the fold. We propose a novel method that extends terrace surfaces above the forelimb of the fold within the extent of deformation determined on the seismic reflection profile, to estimate the sediment thickness after abandonment of the terraces. Furthermore, cosmogenic nuclide (10Be and 21Ne) depth profile dating was used to determine the exposure ages of the two terrace surfaces: 413–673 kyr for T1b and 3.7–5.2 Myr for T3b. Combining the age and deformation amount, the slip rate on the frontal fault ramp within the fold is estimated to be 0.4+0.2/-0.1 mm/yr and 0.17+0.07/-0.03 mm/yr since the abandonment of the T1b and the T3b terrace respectively. These rates represent the recent crustal shortening rate across the Guman fold and likely account for most of the total crustal shortening rate across the Western Kunlun Mountains. However, these rates appear to be notably lower by an order of magnitude compared to the long-term (∼23 Ma) average crustal shortening rate (∼1.1–2.6 mm/yr) in this region. This may indicate a rapid slowing down of the deformation at the scale of the whole Western Kunlun Mountains, possibly related to a regional reorganization.
期刊介绍:
The Journal of Structural Geology publishes process-oriented investigations about structural geology using appropriate combinations of analog and digital field data, seismic reflection data, satellite-derived data, geometric analysis, kinematic analysis, laboratory experiments, computer visualizations, and analogue or numerical modelling on all scales. Contributions are encouraged to draw perspectives from rheology, rock mechanics, geophysics,metamorphism, sedimentology, petroleum geology, economic geology, geodynamics, planetary geology, tectonics and neotectonics to provide a more powerful understanding of deformation processes and systems. Given the visual nature of the discipline, supplementary materials that portray the data and analysis in 3-D or quasi 3-D manners, including the use of videos, and/or graphical abstracts can significantly strengthen the impact of contributions.