10Be Datingof Taheman Large Scale Landslidein Eastern Pamirand Paleoseismic Implications
详细信息
- 责任者：Yuan Zhaode(State Key Laboratory of Earthquake Dynamics ; Institute of Geology ; China Earthquake Administration ; Beijing 100029) ; Chen Jie
- 刊名：Quaternary Sciences
- 出版年：2012
- 卷期：32(3)
- 页码：p.409-416
- issnNo：ISSN1001-7410
- isbnNo：CN11-2708/P
摘要
Large-scale landslides/rock avalanches are significant events that result in erosional degradation of mountains as well as the change of orogenic mass balance,and imperil human populations and their infrastructure.Determining the distribution of landslides through time is the key to assess hazards and for understanding triggering mechanisms,such as climatic change,phases of enhanced earthquake frequency,or post-glacial stress relaxation.However,few studies have been undertaken on large landslides in the high mountains of Central Asia because of the inaccessibility of the region and the associated problems of mapping and sampling for numerical dating.The Taheman landslide is located on the south side of Muztagh Ata(7546m above sea level)just to the north of the 1895 Tashkurgan earthquake(M7)surface rupture in the NE Chinese Pamir,a tectonically active orogen.This paper describes the characteristics of Taheman large scale landslide,with a debris area as 5.1km2 and its volume as 155×106m3(height and width are ca.150m and ca.2km respectively).The landslide is composed of sediment deposit zone,transport zone and detachment zone.Its deposit has a tongue-shaped toe which is marked by numerous sub-parallel,parabolic,and longitudinal ridges.The surface of the deposit is dominated by large,very angular block>1m in diameter.Some blocks almost exceed 20m in length and have jigsaw morphology.Blocks on the surface form an open framework with some sand and fine gravel which is the result of bedrock shattering during transport and emplacement.In order to confine the time of the landslide,six gneiss boulders(length,height and width are all more than 1m)on the surface of the landslides were collected for 10Be exposure dating.All these samples were processed in University of Cincinnati and then measured by accelerator mass spectrometry at PRIME Laboratory in Purdue University.Basic concepts of cosmogenic nuclide dating,sampling and pretreatment are showed in this paper.The six 10Be dating ages are very consistent and indicate their formation 6.8±0.2kaB.P.The consistence suggests TCN exposure dating is an effective method of dating landslides.In addition,gully scale,rock varnish thickness,offset scarp and dating results suggest that the Taheman landslide was not trigged by 1895 Tashkorgan earthquake.Moreover,the methods and parameters used for interpreting TCN data are not yet standardized.Therefore,we attempted to use our six 10Be dating data to set up data reporting standards needed in order to help other scientists to use our data to do more research.