【摘要】 通过对东北二龙湾玛珥湖顶部无扰动岩心显微研究,证明此岩心发育有良好的年纹层。据精确统计,0~5.5cm间为36个年纹层,纹层计年的误差为4%~7%,年纹层厚度为1.1~2mm不等,平均沉积速率为1.53mm/a,5.5cm处对应于1965年。而二龙湾沉积物(从6.5cm到5.5cm)岩心的137Cs比活度值急剧增加,从(4.67±0.29)dpm/g增加到(12.06±0.47)dpm/g,在5.5cm处有一个较为明显的蓄积峰值,这一峰值被确认对应为1963年全球137Cs散落的高峰期。另外据210Pbex比活度CIC模式,5.5cm处约为1962年,这和137Cs比活度曲线的1963年时标相一致。印证了纹层计年的精确性,完全可以建立高分辨率时间序列。更多还原

【Abstract】 Detailed investigations were carried out on the upper undisturbed sediments from Erlongwan maar lake,NE China,which are better annually laminated sediments(varve).Varve couple appears as dark-and light-coloured layers. Based on varve dating of large thin sections under microscope,36 varve couples,with 4%~7% discrepancy,1.1~2 mm varve thickness and 1.53 mm/a rate of sedimentation were found in the upper part of the core(0~5.5 cm),and 5.5 cm correlates to the year of 1965.However,Radiometric dating shows that the highest 137Cs activity appears at 5.5 cm depth,assumed to correlate to the 1963 maximum of emission due to the nuclear bomb testing.137Cs activities increase quickly from 6.5 cm to 5.5 cm(from 4.67±0.29 dpm/g to 12.06±0.47 dpm/g).In addition, By calculating of 210Pbex(CIC),5.5 cm depth corresponds with the 1962.As a result,210Pbex(CIC) and 137Cs dating show a good agreement with the varve dating.Varve dating is exact and varve sediments can offer an effective means of acquiring high-quality palaeoenvironmental records.更多还原