摘要
通过对北京平原南口一孙河断裂南段上下两盘钻孔剖面开展磁性地层学研究,建立了目标钻孔的磁性地层序列。结合沉积物岩石组合特征以及浅部测年数据进行分析,建立了本区第四纪地层格架。断裂两盘地层对比结果表明,南口一孙河断裂南段早更新世、中更新世、晚更新世和全新世垂直落差分别为116.5m,30.Om,4.1m和1.2m,各时代垂直活动速率分别为O.065mm/a,0.046mm/a,0.03mm/a和0.11mm/a。南口-孙河断裂南段活动特征总体表现为早更新世-晚更新世活动较弱,全新世活动强烈的特点。
As one of buried faults in Quaternary in Zhangjiakou-Bohai seismic belt,Nankou-Sunhe Fault is the only one northwest striking active fault in Capital Circle.This fault strikes is from Nankou town in Changping,southeastwards to Qijianfang,Baiquanzhuang,Dongsanqi,Sunhe and Tongzhou,and the fault segment has a general strike of 315° and 80km long.The Northwest segment of fault is from Nankou to Beiqijia and the fault section is SW trending,which controls the Quaternary Machikou-Shahe depression with a maximum Quaternary sediment thickness up to 600m.The Northeast segment of fault is from Beiqijia to Sunhe and the fault section is SE trending,which controls the boundary of Dongba depocenter in Sunyi depression with a maximum Quaternary sediment thickness up from 700m to 800r.Two boreholes are layout in the south part of Nankou-Sunhe fault,that coring rate is above 90％.The geographic coordinates of ZK17 is 40°05′51″N,116°25′40″E and the depth is 416.6m.This number of ZK18 is 40°05′16″N,116°25′32″E and 247.6m.Detailed geologic logging and sample test were done in both of boreholes.Among them,there are 386 paleomagnetic samples and 249 system thermal demagnetization samples （ZK17 hole 140 samples,ZK18 hole 109 samples）; shallow stratigraphic age measured by OSL method,ZK17 sampling depth is 1.2m and 27.0m; ZK18 sampling depth is 3.3m and 25.0m.Magnetostratigraphy was study detailed in the two fault walls,magnetostratigraphic sequence of target boreholes was established.ZK17 hole：0～ 98m positive polarity zone interpreted as Brunhes positive polarity chron,98～ 336m negative polarity zone interpreted as Matsuyama negative chron,117～119m and 191～ 230m positive polarity zone respectively interpreted as Jaramillo and Olduvai positive polarity subchron,309m below positive polarity zone interpreted as Gauss positive polarity chron; ZK18 hole：0～68m positive polarity zone interpreted as Brunhes positive polarity chron,68.0～192.5m negative zone interpreted as Matsuyama negative chron,77 ～ 87m and 129 ～ 153m positive polarity zone respectively interpreted as Jaramillo and Olduvai positive polarity subchron,192.5m below positive polarity zone interpreted as a Gaussian positive polarity chron.Combined with rock association characteristics and dating data in shallow part,the district sequence stratigraphic framework was built up.Late Pleistocene bottom boundary depth of ZK17 and ZK18 are 309m and 192.5m; Middle Pleistocene bottom boundary depth of ZK17 and ZK18 are 98m and 68m; Early Pleistocene bottom boundary depth of ZK17 and ZK18 are 25.7m depth and 21.6m; Holocene bottom boundary depth of ZK17 and ZK18 are 1.0m depth and 0.8m.According to the research of south segment of Beijing plain area Nankou-Sunhe fault,the vertical displacement is 143.5m in Early Pleistocene,30.0m in Middle Pleistocene,4.lm in Late Pleistocene,1.2m in Holocene,and the vertical activity rate is 0.11rm/a,0.03mm/a,0.41mm/a,0.69mm/a correspondingly.The active characteristics of the South segment is that the fault has been of strongly active in Early Pleistocene and Middle Pleistocene and has been of weekly active in Late Pleistocene and Holocene.This active characteristics and the neoteetonics characteristics in south of Beijing show the same law.
出处
《第四纪研究》
CAS
CSCD
北大核心
2014年第2期381-390,共10页
Quaternary Sciences
基金
北京市国土资源局"北京平原区活动断裂监测专项地质调查项目"(批准号:京国土环【2009】308)资助
关键词
磁性地层
南口-孙河断裂
活动速率
第四纪
magnetic stratigraphy
Nankou-Sunhe fault
activity rate
Quaternary
