摘要
在缺少第四纪火山活动的区域,沉积物成为第四纪地质构造和地貌、环境演化等方面研究的主要年代学测量对象。对于老于200ka的沉积物,电子自旋共振(ESR)是潜在的测量方法之一。ESR信号中心会在光晒退或热事件的作用下衰减或"回零"。对于第四纪沉积物而言,在最后一次埋藏事件发生之前,只存在阳光晒退作用,因此了解各ESR信号中心的光晒退特征是准确测量其年代的关键问题。文中简单介绍了ESR测年方法的理论基础,以及剂量率(D)和等效剂量(ED)的测量方法,总结了各ESR信号中心的光晒退特征,回顾了它们在地质年代学中的应用。对各信号中心的光晒退特征和应用的对比表明,石英Ti心ESR信号比较适合第四纪沉积物年代学测量,是第四纪沉积物年代学研究的又一有效手段。
Because of lack of Quaternary volcano activity in China,Quaternary sediments become the main dating material in the study of geological structure,topographic feature and environment evolution,etc.ESR is a potential dating method for the sediments older than 200ka.After sunlight bleaching or heating,the quartz ESR signals,including E'-,Ge-,Al-,Ti-center,can attenuate or be reset.The sediments deposited during Quaternary period only have the effect of sunlight bleaching before the last burial time.Therefore,the sunlight bleaching characteristics of ESR signal centers is one of the most important factors in ESR dating.In this study,the paper firstly makes a simple introduction on the ESR theoretical basis and the measuring process of dose rate(D) and equivalent dose(ED),and then,reviews the sunlight bleaching characteristics and the applications in Quaternary geochronology of different ESR signal centers.The E'-center ESR signal increases with the sunlight bleaching during first 72 hours,it is not suitable for the sediment dating.Ge-center ESR signal is bleachable and can be reset after several hours sunlight bleaching,so,it is the most light sensitive signal center.However,it is very difficult to measure the Ge-center ESR signal in laboratory because it is very weak.Al-center can attenuate 20 percent after 2 hours sunlight bleaching and after tens to hundreds of hours bleaching it still maintains a stable residual signal,50-80 percent.The remnant signals are not equal under different sediment environment.We usually gain a bigger age using Al-center ESR signal for the uncertain remnant.Ti-center ESR signals can be totally bleached after tens to hundreds of hours sunlight bleaching,and this ESR signal also has enough intensity for measurements.According to the review of all the ESR signal centers' sunlight bleaching characteristics and several successful application examples,we suggest that Ti-center ESR signal is more suitable than others for the ESR dating of Quaternary sediment.
出处
《地震地质》
EI
CSCD
北大核心
2011年第2期490-498,共9页
Seismology and Geology
基金
地震动力学国家重点实验室自主研究课题(LED2009A04)
国家自然科学基金(40902051)共同资助