摘要
在渭河盆地东南缘的华山山前断裂北侧,对分布于陕西华县莲花寺一带数平方千米的黄土之下松散堆积的角砾岩的成因存在多种不同的认识,笔者根据地貌和堆积物特征支持其为高速远程滑坡的观点,并确定滑坡分为早、晚两期,后期还叠加了崩塌。野外调查发现覆盖于滑坡体上的黄土最大厚度达9m,根据第四纪黄土平均堆积速率估算的年龄与前人认为的滑坡时代大相径庭。为了准确厘定陕西华县莲花寺滑坡的形成时代,对覆盖于滑坡体上的黄土进行了5个剖面的样品采集,应用光释光（OSL）方法开展了系统的测年,结果5个剖面角砾岩之上最底部的黄土年龄在 130.2±5.6-187.3±7.7ka之间,显示角砾岩之上堆积的黄土并不是同时形成的,其堆积的先后可能与古地形有关,角砾岩之上最底部黄土的最老年龄（187.3±7.7ka）代表了陕西华县莲花寺第二次滑坡形成时代的上限,即陕西华县莲花寺高速远程滑坡至少形成于18.7万年前。这是首次准确获得陕西华县莲花寺古滑坡的时代上限,亦是目前国内报道最老的高速远程滑坡,对滑坡的研究具有重要意义。同时,讨论了华县莲花寺高速远程滑坡的诱因可能是华山山前断裂的地震活动。
The study area is located in transition zone between the Qinling orogenic belt and Weihe basin of the southeast in Ordos block,is about 15km east of Huaxian,Shaanxi Province.Huashan piedmont fault is a crust-structural and geomorphologic boundary between the Qinling orogenic belt and the east of Weihe basin.The loose-accumulated breccia,in an area of 4-6km2 occurs under the loess in north-part of Huashan piedmont fault,Lianhuasi area in Huaxian.There are several viewpoints of origin of loose-accumulated breccia under loess.According to the field survey of landform characteristics and deposits,the authors prefer the viewpoint of high-speed remote landslide.We found that the landslide is composed of slide bed,slip,sliding surface,the posterior wall of the landslide,landslide perimeter,landslides depression and so on; the landslides can be divided into early and late two stages,and collapse superimposed in late stage landslide.Early stage landslide is corresponding to the chair circle landscape in hilltop of Zhangjiashan,breccia is deposits in Baiya Lake hole depth 60.10m to 70.23m,with a thickness of 10.13m.Late stage landslide corresponds to lower chair circle landscape in the southern of Baoyu valley,breccia is deposits in Baiya Lake hole depth 33.74-50.15m in thickness of 16.41m.What is the age of late stage landslide？Most researchers think that it is associated with MS=5 1/2 Huaxian earthquakes of November 3,1072 or MS=8 Huaxian earthquakes of January 23,1556.However,we find that the maximum thickness of loess covered in the landslides is up to 9m during the field investigation,so,it must be formed in at least the tens of thousands years ago according to the Quaternary loess accretion rate projections.In order to constraint accurately the age of Lianhuasi landslides of Huaxian,Shaanxi Province,we gather 17 OSL samples from loess accumulated above late stage landslide in five cross section selected,breccia were collected.We carried out OSL dating of bottom of the loess cover on landslides from five cross section are from 130.2±5.6ka to 187.3±7.7ka,it means that bottom loess cover on landslides formed in different time,it may be related to the ancient landform.The oldest age have been get 187.3±7.7kaB.P., it represent the late stage landslides of Lianhuasi of Huaxian formed in 187.3kaB.P.ago.It is the first time to accurately obtain the upper boundary of age of late landslides of Lianhuasi of Huaxian,this paper reports that it is the oldest highspeed and runout landslide in China,it is of a very important significance in landslide research.So that,the reasonable interpretation of Huaxian Lianhuasi landslides is induced by seismic activity of Huashan piedmont fault.
出处
《第四纪研究》
CAS
CSCD
北大核心
2013年第5期1005-1015,共11页
Quaternary Sciences
基金
中国地质调查局地质大调查项目"秦岭北缘断裂带构造特征及构造地貌过程研究"(批准号:1212011120102)
深部探测技术与实验研究专项项目(批准号:Sinoproble-06)共同资助
关键词
高速远程滑坡
古滑坡
华县莲花寺滑坡
黄土OSL测年
华山山前断裂
high-speed and long-distance landslide, ancient landslide, Lianhuasi landslide of Huaxian,loess OSL dating,Huashan piedmont fault
