叠溪古堰塞湖地震扰动沉积物特征  

Characteristics of Diexi ancient barrier lake sediments brought about by seismic disturbances,Sichuan,China

作　　者：沈曼[1] 王小群[1] 许峰[1] 周辀 崔亚昆 

机构地区：[1]地质灾害防治与地质环境保护国家重点实验室(成都理工大学),成都610059

出　　处：《成都理工大学学报（自然科学版）》2014年第3期369-377,共9页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家自然科学基金资助项目(41072230);地质灾害防治与地质环境保护国家重点实验室研究基金资助项目(SKLGP2012Z007)

摘　　要：探讨湖相沉积物的粒度特征，研究大地震发生的周期。岷江上游叠溪古堰塞湖沉积物中保存了大量气候环境信息和地质环境信息。通过地面调查、岩心观察、粒度测试分析加以测龄、环境气候分析的方法，对叠溪古堰塞湖全断面岩心中具有明显扰动特征的扰动层及其下卧层（下接触层）土壤进行分析。结果表明，岩心中存在10个明显的扰动层，其扰动现象与叠溪古堰塞湖地表出露的扰动现象一致。扰动层粒度总体上大于其下卧层（下接触层）。扰动层沉积物的平均粒径（d 50）在0．0068～0．0107 mm，大多数为0．008 mm 左右。扰动层的粉粒含量波动较大，其下卧层粉粒的质量分数大多在64％左右；相对应黏粒的质量分数，扰动层多在33％左右，而其下卧层波动较大。这些扰动层与下卧层的特征反映了湖相沉积物在沉积过程中受到外力影响而发生的变化。结合测龄资料，初步推测大地震发生的周期大约是850 a。In order to study the earthquake cycle, it is necessary to approach the grain size characteristics of lake sediments.The sediments in the Diexi ancient lake located at the upstream of the Minjiang River contain a lot of information about climate and geological environments.The soils in the disturbed layers and the underlying layer （lower contact layer ） with obvious disturbance characteristics in the full section cores of the Diexi ancient lake are analyzed by using the methods such as ground investigation,core observation,measurement and dating of particle size and climate analysis.The results show that there are ten obvious disturbed layers,whose disturbing phenomena are the same with that outcropped on the surface of the Diexi ancient lake.The particle size in the disturbed layer is larger than that in the lower contact layer.The particle diameter （d 50 ）of the sediments in the disturbed layers is 0.0068~0.0107 mm and that of the most sediments is about 0.008 mm.The silt content of the disturbed layers fluctuates a lot and the mass fraction of its underlying layer powder is mostly about 64%.On the other hand,the mass fraction of the clay in the disturbance layers is about 33%,while that of the underlying layer fluctuates a lot.The characteristics of these disturbance layers and underlying layers reflect the changes of the lacustrine sediments under the influence of the external force during the deposition process.Combined with the data of the age dating,the result of the initial speculation about the earthquake cycle is about 850 a.

关 键 词：湖相沉积物 粒度特征 扰动层 地震周期 

分 类 号：P534.63[天文地球—第四纪地质学]