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

IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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引用次数: 0

摘要

表征前陆的活动变形对于了解活动性收缩造山带的区域构造演化动态尤为重要。我们的研究重点是古曼褶皱,它是西昆仑山(中国新疆)山麓最突出的褶皱推覆带之一。生长在推断盲断层之上的反斜线逐渐使河流阶地发生变形。然而,当时的阶地表面被掩埋在褶皱以北的年轻沉积物之下。我们提出了一种新方法,在地震反射剖面确定的变形范围内,将阶地表面延伸到褶皱前肢以上,以估算阶地废弃后的沉积厚度。此外,还利用宇宙成因核素(10Be 和 21Ne)深度剖面测年法确定了两个阶地表面的出露年代:T1b 为 413-673 kyr,T3b 为 3.7-5.2 Myr。结合年龄和变形量,估计自 T1b 和 T3b 台地废弃以来,褶皱内正面断层斜坡的滑动速率分别为 0.4+0.2/-0.1 毫米/年和 0.17+0.07/-0.03 毫米/年。这些速率代表了古曼褶皱近期的地壳缩短速率,可能占整个西昆仑山地壳缩短速率的大部分。然而,与该地区长期(∼23 Ma)平均地壳缩短速率(∼1.1-2.6 mm/yr)相比,这些速率似乎明显低了一个数量级。这可能表明在整个西昆仑山范围内,变形的速度迅速减慢,可能与区域重组有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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.

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来源期刊
Journal of Structural Geology
Journal of Structural Geology 地学-地球科学综合
CiteScore
6.00
自引率
19.40%
发文量
192
审稿时长
15.7 weeks
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.
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