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首页> 外文OA文献 >The late Quaternary slip-rate of the Har-Us-Nuur fault (Mongolian Altai) from cosmogenic Be-10 and luminescence dating
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The late Quaternary slip-rate of the Har-Us-Nuur fault (Mongolian Altai) from cosmogenic Be-10 and luminescence dating

机译：宇宙成因Be-10和发光测年的Har-Us-Nuur断层（蒙古阿尔泰）的晚期第四纪滑动速率

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The Altai range (western Mongolia) accommodates NNE-SSW shortening across the northern India-Eurasia collision zone by dextral slip on faults trending NNW-SSE, and anticlockwise, vertical-axis rotations of fault-bounded blocks. However, fault slip-rates and the way in which faulting evolves over time are poorly understood, and form the motivation for this study. We focussed on the Har-Us-Nuur fault, a major transpressional fault bounding the eastern margin of the Altai. Three abandoned alluvial fan surfaces, each displaced right-laterally by the fault, were targeted for dating with cosmogenic 10Be and quartz optically stimulated luminescence (OSL). The first surface (A2) shows an exponential decrease in 10Be with increasing depth, with a significant inherited component. Modelling this profile yielded a minimum age of 74.1 ka. Material from the same sampling pit was dated at ~ 19 ka with OSL, but we consider this younger age to be incorrect, possibly due to feldspar contamination or abnormal quartz OSL characteristics. The A2 surface is displaced by 175 m, implying a (maximum) dextral slip-rate of 2.4 ± 0.4 mm yr- 1. A second fan surface (F1) was dated at ~ 6 ka with OSL and shows little variation in 10Be with depth, consistent with this young age. The inherited component is higher than for A2, indicating contrasting levels of inheritance for different periods of fan aggradation. A final surface (F2) shows scattered 10Be concentrations and lacks material suitable for OSL, so cannot be dated precisely. Using the total vertical displacement across the fault, we place the initiation of movement on the fault at ~ 2 Ma, significantly later than the late Oligocene to Miocene (28-5 Ma) onset of shortening in the Altai region. This suggests that deformation in the Altai has widened over time to incorporate new faults at the range margins (such as Har-Us-Nuur), possibly because older faults in the range interior have rotated about vertical axes into orientations that require work to be done against gravity. © 2009 Elsevier B.V. All rights reserved.
机译：阿尔泰山脉（蒙古西部）可通过印度北部-欧亚大陆碰撞带上的NNE-SSW缩短，这是由于倾向NNW-SSE的断层发生右旋滑移，以及断层界块的逆时针垂直轴旋转。但是，人们对断层滑移率和断层随时间演化的方式知之甚少，并形成了本研究的动机。我们的重点是Har-Us-Nuur断层，这是一个主要的压断层，其边界位于阿尔泰东部边缘。三个废弃的冲积扇面，每个都由断层向右偏移，目标是与宇宙成因的10Be和石英光学激发发光（OSL）约会。第一表面（A2）随深度的增加显示10Be呈指数下降，并且具有显着的遗传成分。对此轮廓进行建模后，最小年龄为74.1 ka。来自同一采样坑的材料的OSL年代约为19ka，但是我们认为这个年轻年龄是不正确的，这可能是由于长石污染或石英OSL特性异常造成的。 A2表面位移175 m，这意味着（最大）右旋滑移率为2.4±0.4 mm yr-1。第二个风扇表面（F1）的OSL年代约为〜6 ka，并且深度随10Be的变化很小，与此年龄相符。继承的分量比A2高，表明在不同的扇形凝集时间段内，继承的对比级别不同。最终表面（F2）显示出分散的10Be浓度，并且缺乏适用于OSL的材料，因此无法准确确定日期。利用整个断层的垂直位移，我们将运动的始端置于〜2 Ma处，明显晚于阿尔泰地区的渐新世至中新世（28-5 Ma）缩短开始。这表明阿尔泰地区的变形随着时间的推移而扩大，以在距离边缘合并新的断层（例如Har-Us-Nuur），这可能是因为山峰内部的较早断层已围绕垂直轴旋转成需要完成工作的方向抵抗重力。 ©2009 Elsevier B.V.保留所有权利。

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