唐山孙家楼探槽光释光测年及其对古地震事件的指示意义
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摘要
利用细颗粒(4～11μm)石英简单多片再生法(SMAR)光释光测年技术对横跨1976年唐山地震孙家楼探槽剖面中的样品进行系统测年,研究表明:样品的光释光信号以快组份为主,适合光释光测年。根据年龄数据和深度建立年龄-深度曲线和函数,推算出了剖面的沉积速率。研究结果表明,该地区50～7.16 ka以来,断层两侧沉积速率曲线为两条平行直线。说明该剖面揭示此期间沉积环境稳定,无构造运动,沉积速率很小,为0.03 m/ka,平行线之间0.6 m的距离可能是1976年唐山地震造成。75～50 ka期间,主断层在～50 ka的活动造成地层沉积速率增大,为～0.1 m/ka。同期的次断层活动造成断层西侧沉积速率为东侧的两倍,即～0.2 m/ka。可见,研究区沉积速率发生变化的主要因素是构造运动,非气候成因。
We use simplified multiple aliquot regenerative-dose(SMAR) protocol from fine grain quartz(4~11μm) to systematically date samples from Sunjialou trench across Tangshan earthquake zone in 1976.OSL signals of these samples dominated by fast component show that they are suitable for OSL dating.On the basis of the optical ages and the burial depth of samples,the age-depth curve and function of the trench are obtained.Through it we inferred depositional rate.The results suggest that depositional rate curves on both sides of the fault show two parallels between 50 and 7.16 ka,which indicates sedimentary environment are stable and no tectonic movement happened during that time interval.The depositional rate is about 0.03 m/ka and 0.6 meters distance in the range of two parallels is vertical offsets generated by the 1976 Tangshan earthquake.Activity caused by the main fault in about 50 ka leads to depositional rate increase,which is 0.1 m/ka.Coeval activity in the secondary faults causes depositional rate in western segment about twice that of eastern segment,which is 0.2 m/ka.In conclusion,tectonic movement is main factor for depositional rate change in study area but climate change.The depositional rate change may be useful approaches for the palaeoseismic events.
We use simplified multiple aliquot regenerative-dose(SMAR) protocol from fine grain quartz(4~11μm) to systematically date samples from Sunjialou trench across Tangshan earthquake zone in 1976.OSL signals of these samples dominated by fast component show that they are suitable for OSL dating.On the basis of the optical ages and the burial depth of samples,the age-depth curve and function of the trench are obtained.Through it we inferred depositional rate.The results suggest that depositional rate curves on both sides of the fault show two parallels between 50 and 7.16 ka,which indicates sedimentary environment are stable and no tectonic movement happened during that time interval.The depositional rate is about 0.03 m/ka and 0.6 meters distance in the range of two parallels is vertical offsets generated by the 1976 Tangshan earthquake.Activity caused by the main fault in about 50 ka leads to depositional rate increase,which is 0.1 m/ka.Coeval activity in the secondary faults causes depositional rate in western segment about twice that of eastern segment,which is 0.2 m/ka.In conclusion,tectonic movement is main factor for depositional rate change in study area but climate change.The depositional rate change may be useful approaches for the palaeoseismic events.
引文
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9 Aitken M J.Thermoluminescence dating[M].London:Aca-demic Press,1985.
10 Aitken M J.An introduction to optical dating[M].Oxford:Oxford University Press,1998.
11 Lu Y C,Zhang J Z and Xie J.Thermoluminescence datingof loss and paleosols from the Lantian section,Shaanxi Prov-ince,China[J].Quaternary Science Reviews,1988,7(3-4):245-250.
12 Duller H A T.Distinguishing quartz and feldspar in singlegrain luminescence measurements[J].Radiation Measure-ments,2003,37:161-165.
2郭慧,江娃利,谢新生.钻孔与探槽揭示1976年河北唐山Ms7.8地震发震构造晚第四纪强震活动特征[J].中国科学(地球科学),2011,41:1009-1028.(Guo Hui,Jiang Wali and Xie Xinsheng.Late-Quaternary strong earth-quakes on the seismogenic fault of the 1976 Ms7.8 Tangshanearthquake,Hebei,as revealed by drilling and trenching[J].Science China(Earth Sciences),2011,54:1 696-1 715)
3王旭龙,卢演俦,李晓妮.细颗粒石英光释光测年:简单多片再生法[J].地震地质,2005b,27(4):615-623.(Wang Xulong,Lu Yanchou and Li Xiaoni.Luminescencedating of fine-grained quartz in Chinese loess-Simplified mul-tiple aliquot regenerative-dose(MAR)protocol[J].Seismolo-gy and Geology,2005b,27(4):615-623)
4 Wang X L,Lu Y C and Zhao H.On the performances of thesingle-aliquot regenerative-dose(SAR)protocol for Chi-nese loess:fine quartz and polymineral grains[J].RadiationMeasurements,2006a,41:1-8.
5 Lu Y C,Wang X L and Wintle A G.A new OSL chronologyfor dust accumulation in the last 130 000 years for the Chi-nese Loess Plateau[J].Quaternary Research,2007,67:152-160.
6赵俊香,等.山西忻定盆地断层崩积楔OSL年龄及其对古地震事件的指示意义[J].现代地质,2009,23(6):1 022-1 029.(Zhao Junxiang,et al.OSL age of fault col-lapse wedge in Xinding basin,Shanxi province and its signif-icance for paleoearthquake events[J].Geoscience,2009,23(6):1022-1029)
7赵俊香,等.断层崩积楔单片再生法光释光测年:以山西忻定盆地西田探槽为例[J].现代地质,2011,25(2):356-362.(Zhao Junxiang,et al.OSL dating of fault collapsewedge using SAR method:taking the Xitian trench of Xindingbasin,Shanxi as an example[J].Geoscience,2011,25(2):356-362)
8王旭龙,李晓妮,卢演俦.红光固体二极管点阵在释光测中的光照应用[J].海洋地质与第四纪地质,2004,24:133-138.(Wang Xulong,Li Xiaoni and Lu Yanchou.RedLED and its application to luminescence lighting[J].MarineGeology and Quaternary Geology,2004.24:133-138)
9 Aitken M J.Thermoluminescence dating[M].London:Aca-demic Press,1985.
10 Aitken M J.An introduction to optical dating[M].Oxford:Oxford University Press,1998.
11 Lu Y C,Zhang J Z and Xie J.Thermoluminescence datingof loss and paleosols from the Lantian section,Shaanxi Prov-ince,China[J].Quaternary Science Reviews,1988,7(3-4):245-250.
12 Duller H A T.Distinguishing quartz and feldspar in singlegrain luminescence measurements[J].Radiation Measure-ments,2003,37:161-165.
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