| A Preliminary Study on the Soft–Sediment Deformation Structures
in the Late Quaternary Lacustrine Sediments at Tashkorgan,
Northeastern Pamir, China |
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| 作者姓名： | LIANG Lianji DAI Fuchu JIANG Hanchao ZHONG Ning |
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| 摘 要： | This study identified soft–sediment deformation structures(SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo–dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS 14 C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yr BP and 22710±80 yr BP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.
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| 关 键 词： | soft–sediment deformation structures lacustrine sediment Pamir liquefaction thixotropy paleo–seismicity |
| 修稿时间： | 2018/3/8 0:00:00 |
A Preliminary Study on the Soft–Sediment Deformation Structures in the Late Quaternary Lacustrine Sediments at Tashkorgan,Northeastern Pamir,China |
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| Authors: | LIANG Lianji DAI Fuchu JIANG Hanchao and ZHONG Ning |
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| Institution: | 1. College of Architecture and Civil Engineering, Beijing University of Technology, China;2. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, China |
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| Abstract: | This study identified soft–sediment deformation structures (SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo–dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M>6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS 14C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China. |
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| Keywords: | soft– sediment deformation structures lacustrine sediment Pamir liquefaction thixotropy paleo– seismicity |
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