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Title:: Discussion of the Origin of the Soft-sediment Deformation Structures in Paleo-dammed Lake Sediments in the Upper Reaches of the Minjiang River

作者:: 张斌¹; 2; 王萍¹; 王建存¹; 2; (1.中国地震局地质研究所地震动力学国家重点实验室,北京 100029; 2.中国地质大学地球科学与资源学院(北京),北京 100083)

Author(s):: ZHANG Bin¹; 2; WANG Ping¹; WANG Jian-cun¹; 2; (1.State Key Laboratory of Earthquake Dynamics,Institute of Geology,CEA,Beijing 100029,China)(2.School of the Earth Sciences and Resource,China University of Geosciences,Beijing 100083,China)

Keywords:: soft-sediment deformation; seismites; paleo-earthquake; dammed lake; Minjiang River

摘要:: 对在岷江上游及其支流河谷中的晚第四纪古堰塞湖地层中发现的大量软沉积物变形构造的类型、特征和成因进行了分析,发现这些软沉积物变形构造分为两类:一类是小型的层内变形构造,如液化卷曲变形、泄水构造、负荷构造、阶梯状微断裂等,其形成与软沉积物的塑性变形、液化和流动作用相关; 另一类是崩(滑)塌体对软沉积物的扰动形成的大型褶曲构造。通过与其它成因的软沉积物变形构造的对比以及对区域构造环境的分析,得出地震、崩塌和滑坡等灾害性地质事件是造成河谷区古堰塞湖地层中软沉积物变形构造发育的最可能的驱动机制。

Abstract:: Paleo-dammed lake sediments in the upper reaches of the Minjiang River and its tributaries show several types of deformational structures that are interpreted as seismites.In this paper,we analyze the types and characteristics of these deformation.We classify the structures into two types:the small-scale deformations,which are related to the plastic deformation,liquefaction and fluidization processes of the soft sediment.Another is the large-scale folds formed by the disturbance of the collapse masses(slip block).The comparison with other soft-sediment deformation structures and study of the seismotectonic environment indicate that the main trigger factors for deformation were seismic shocks,collapse and landslide induced by the earthquake.