苏干湖沉积物纹层计年和^(210)Pb，^(137)Cs测年对比

Comparison of varve chronology and ^(210)pb,^(137)Cs dating from the Sugan Lake sediment

通过对西北干旱区苏干湖表层沉积物的年纹层计数定年和^(210)Pb,^(137)Cs测年结果对比发现:^(137)Cs测年结果在8.5 cm出现最高蓄积峰,对应1963年世界核爆高峰期,但在同一层位^(210)Pb测年结果则是1972年,存在较大的偏差.年纹层沉积速率达0.31 cm/a,而根据CRS模式建立的^(210)Pb沉积速率为0.30 cm/a.年纹层反映的沉积速率和^(210)Pb测年结果基本一致,互相验证了两者测年的可靠性.^(137)Cs测年则存在蓄积峰向上迁移的现象,在西北干旱区湖泊使用^(137)Cs测年过程中需引起注意.

A detailed examination of sedimentary cores retrieved from Sugan Lake in the northern Qaidam Basin of the northwest China＇s Tibetan Plateau reveals that fine laminated beddings （varve） formed in the sediments. Radiometric dating shows that the highest ^137Cs activity appeared at 8.5 cm depth, which correlated with the 1963 maximum of emission due to the nuclear bomb testing. However the ^210Pb dating result shows a different year （1972） in the same depth. Varve chronology result shows a great agreement with ^210Pb dating in the upper part of core. ^137Cs dating result shows deviation in dating sediment rate. It is indicated that the peak of the ^137Cs would move from lower sediment layer to the upper one. Therefore, ^137Cs dating technology may not be valid in determing lake sediment of an arid region.