Late Pleistocene slip rate of the Chaman fault based on 10Be exposure dating of offset geomorphic surfaces near Kabul, Afghanistan
Late Pleistocene slip rate of the Chaman fault based on 10Be exposure dating of offset geomorphic surfaces near Kabul, Afghanistan
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基于阿富汗喀布尔附近偏移地貌表面 10Be 暴露测年的查曼断层晚更新世滑动率
DOI：
10.1016/j.tecto.2020.228593
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发表时间：
2020
期刊：
影响因子：
2.9
通讯作者：
Tsutsumi Hiroyuki
中科院分区：
文献类型：
--
作者：
Shnizai Zakeria;Matsushi Yuki;Tsutsumi Hiroyuki
根据冲积扇面10be测年，首次报道了阿富汗北部查曼断裂带晚更新世左旋滑动速率。实地测绘加上对CORONA和ALOS PRISM卫星图像以及阴影地形和地形数据的分析，使我们能够在喀布尔以南的瓦尔达克省两个位移冲积扇（Ghat Bandakul和Azadkhail）的断裂带上确定穿透点。我们根据深埋石英岩砂岩巨石和鹅卵石的10be陆地宇宙成因核素（TCN）定年，对偏置冲积扇的年龄进行了限定。的山路Bandakul冲积球迷抵消165 ± 15 米和235 ± 24 m,为which10Be TCN模型年龄平均46.9 ±3.5 可以和66.6±4.9 可以,分别产生的滑移率3.5 ± 0.4毫米/年。在Azadkhail遗址，我们发现了两个相互抵消的梯田。基于111.2 ± 10.5 kyr年龄的地貌面500 ± 50 m偏移量，我们得到了4.5 ± 0.6 mm/yr的滑移率。结合800 ± 70 m的左偏置匹配和平均年龄176.8 ± 17.1 kyr，得到相同的地貌滑移率为4.5 ± 0.6 mm/yr。这些滑动速率远低于以前沿查曼断层南部获得的地质、地貌和大地测量定义的滑动速率。结果表明，随着向东北方向距离的增加，断层滑动率有明显的减小趋势。观测结果表明，该断层的南部容纳了印度板块和欧亚板块之间相对运动的大部分断层平行分量。阿富汗查曼断裂带较低的滑动速率可能是由于从查曼断裂带向北伸展的Gardez和Mokur断裂带的左侧向剪切转移所致。
We report the first late Pleistocene left-lateral slip rate of the northern Chaman fault in Afghanistan based on10Be dating of offset alluvial fan surfaces. Field mapping complemented with the analysis of CORONA and ALOS PRISM satellite images and shaded relief and topographic data allows us to identify piercing points across the fault zone at two displaced alluvial fans (Ghat Bandakul and Azadkhail) at Wardak Province south of Kabul. We constrain the ages of offset alluvial fans based on10Be terrestrial cosmogenic nuclides (TCN) dating of well-embedded quartzite sandstone boulders and cobbles. The Ghat Bandakul alluvial fans are offset at 165 ± 15 m and 235 ± 24 m, for which10Be TCN model ages average 46.9 ± 3.5 kyr and 66.6 ± 4.9 kyr, respectively, yielding a slip rate of 3.5 ± 0.4 mm/yr. At the Azadkhail site, we identified two offset terraces. Based on 500 ± 50 m offset of a geomorphic surface with 111.2 ± 10.5 kyr age, we obtain a slip rate of 4.5 ± 0.6 mm/yr. Combining the 800 ± 70 m left-lateral offset matching with an average age of 176.8 ± 17.1 kyr for the fan yields the same geomorphic slip rate of 4.5 ± 0.6 mm/yr. These slip rates are considerably lower than geologically, geomorphologically, and geodetically defined slip rates previously obtained along the southern Chaman fault. These results show a clear trend of decreasing fault slip rate with increasing distance to the northeast. The observations suggest that the southern portion of the fault accommodates most of the fault-parallel component of relative motion between the Indian and Eurasian plates. The lower slip rate of the Chaman fault in Afghanistan may be explained by the transfer of the left-lateral shear onto the Gardez and Mokur faults that splay northward from the Chaman fault.