热带地理 ›› 2013, Vol. 33 ›› Issue (5): 533-541.

• 论文 • 上一篇    下一篇

福州盆地残留沼泽沉积的137Cs同位素定年与沉积环境演化

章桂芳1,2,郑 卓1,Barry Rollet3,黄康有1,乐远福1,朱光祺1   

  1. 1.中山大学 地球科学系,广州 510275;2.广东省地质过程与矿产资源探查重点实验室,广州 510275; 3.Department of Anthropology,University of Hawaii,Honolulu,USA
  • 出版日期:2013-10-02 发布日期:2013-10-02
  • 基金资助:
    国家自然科学基金(41072128);中山大学中央高校基本科研业务费专项资金(10lgzd08;11lgpy53)

137Cs Dating and Sedimentary Environment Evolution of a Residual Swamp in Fuzhou Basin

ZHANG Guifang,ZHENG Zhuo,BARRY Rollet,HUANG Kangyou,YUE Yuanfu,ZHU Guangqi   

  • Online:2013-10-02 Published:2013-10-02

摘要: 对福州盆地鳌峰洲残留沼泽沉积540 cm的FZ1钻孔进行了元素地球化学和137Cs以及加速器碳同位素(AMS 14C)测年。结果表明:钻孔存在2段不同的沉积环境,下部为洪冲积,上部为沼泽沉积,然而2段各自的沉积环境则相当稳定。137Cs测试在沼泽相稳定沉积出现的3个蓄积峰与北半球的放射性年代标尺可以对比。根据蓄积峰年代和插值后获得的钻孔底部年龄约为公元1950年,与钻孔底部的AMS 14C测年基本吻合,该结果表明采用137Cs测年方法定年是可行的。沉积速率研究揭示:20世纪50年代初至60年代中,近代洪冲积在福州盆地断块下沉区沉积速率极快,钻孔下部粉砂质淤泥的沉积速率达到20.9 cm/a;随着闽江下游盆地平原与河流变迁以及心滩的形成,原来的水道快速淤积演变为陆地沼泽环境,沉积速率开始逐步减小:20世纪60―70年代中降为9.9 cm/a,70―80年代中继续下降为7.1 cm/a,80年代中之后降为3.1 cm/a。福州盆地中心区的高沉积速率与全新世断块差异性活动存在着密切关系。

关键词: 137Cs, 沉积速率, 残留沼泽, 沉积环境, 福州盆地

Abstract: A 540 cm long sediment core was collected from a residual swamp in Fuzhou basin. Element geochemical, 137Cs and 14C isotopic dating techniques were applied to determine recent sedimentation rates. The results indicated that there were two sedimentary environments for the core. The sedimentary environment of the lower part was proluvial-alluvial and the upper part was swamp. However, both of them were very stable. The three concentrations of 137Cs from swamp sediment were in excellent agreement with the 137Cs fallout activities of the northern hemisphere. The interpolated age of the core bottom was 1950, agreeing with the dating result of 14C, suggesting the 137Cs dating result of this core was reliable. The sedimentation rates showed that the proluvial-alluvial sediment was very rapid in the subsiding area of Fuzhou Basin from early 1950s to middle 1960s which was about 20.9 cm/a. With the change of the basins and plains and the development of Channel Bars in the lower reaches of the Minjiang River, the broad channel changed to the swamp, and the sedimentation rate was decreasing: from middle 1960s to middle 1970s, it was about 9.9 cm/a; and from middle 1970s to middle 1980s, it was about 7.1 cm/a; and later, it was about 3.1 cm/a. The extremely large sedimentation rates in the study area were closely related to the different activities of fault blocks in Fuzhou Basin.

Key words: 137Cs, sedimentation rate, residual swamp, Sedimentary enviornment, Fuzhou Basin