[an error occurred while processing this directive] 高校地质学报 2000, 6(1) 106-115 DOI:     ISSN: 1006-7493 CN: 32-1440/P

本期目录 | 下期目录 | 过刊浏览 | 高级检索                                                            [打印本页]   [关闭]
文章目录
扩展功能
本文信息
Supporting info
PDF(2309KB)
[HTML全文]
参考文献[PDF]
参考文献
服务与反馈
把本文推荐给朋友
加入我的书架
加入引用管理器
引用本文
Email Alert
文章反馈
浏览反馈信息
本文关键词相关文章
本文作者相关文章
冯洪真
刘家润
施贵军
PubMed
Article by
Article by
Article by
湖北宜昌地区寒武系—下奥陶统的碳氧同位素记录
冯洪真, 刘家润, 施贵军
南京大学 地球科学系,江苏 南京 210093
摘要: 对宜昌地区寒武系和下奥陶统的碳酸盐碳、氧同位素进行测定,所得δ18O大 于-10‰且与δ13C不相关,表明研究区碳酸盐样品基本上保存了碳、氧同位素的初 始比值。δ18O在白云岩样品中呈现正漂移而在非白云岩样品中呈现负漂移,认为δ 18O反映海水古盐度变化,即δ18O随着古盐度升高而增大;δ13 C在缺氧沉积物中呈现负漂移,但负漂移的δ13C却不限于缺氧沉积物,推测δ13 C可能反映古海洋的初级生产力,即δ13C随着初级生产力的提高而降低。研究还指 出,由于Z值与δ13C密切正相关(相关系数为0.99),综合运用δ18O和δ 13C的经典盐度公式不适用于研究区古盐度环境的重建。
关键词
Records of Carbon and Oxygen Isotopes from the Cambrian and Lower Ordovician Carbonates in Yichang Area, Hubei Province
FENG Hong-zhen, LIU Jia-run, SHI Gui-jun
Department of Earth Sciences, Nanjing University, Nanjing, 210093 China
Abstract: The carbonate samples studied in this paper wer e collected from the classic sections of Cambrian and Lower Ordovician in th e Yichang area, Hubei province. The results of C- and O-isotope analysis demon strate that δ18O is smaller than or close to -10‰ and does not correlat e with δ13C, suggesting a basically complete preservation of primary rati os of C- and O-isotopes in these carbonate samples.   The δ18O profile from the Cambrian to the Lower Ordovician in the Yichang area drifts positively in dolomite horizons and negatively in non-dolom ite horizons. Such a fluctuation in O-isotopic compositions probably reflects p aleoceanic variations in salinity, i.e. large δ18O indicates increas e in paleosalinity. The Z value is calculated in this study to trace quantitatively the changes of paleosalinity. However, the correlation coefficient is only 0.43 between the Z v alue and δ18O but up to 0.99 between the Z value and δ13C.This mea ns that t he Z value mainly reflects changes in C-isotopic compositions and is not suitab le for the reconstruction of paleosalinity in the investigated area. The δ1 3C profile from the Cambrian to the Lower Ordovician in the Yichang area drift s negatively in anoxic sediments (e.g. in black shales of the lower Shujingtuo F ormation), but negative fluctuations are no t limited to anoxic sediments. They also occur in oxic sediments (e. g. in the S hipai, Xiping and Nanjinguan Format ion). This suggests that δ13C, whether in oxic or anoxic sediments, is po ssibly related to the primary productivity of the ancient marine environ ment s. When the black shales of the Shuijingtuo Formation were deposited, abundant p lanktonic organisms were accumulated to the seafloor. The fresh organic material s from these planktons were then consumed by sulfate-reduction bacterial, leadi ng t o the release of CO2 with lower δ13C and the formation of carbonates by the combination of such CO2 with some metal ions . We believe that the intensity of sulfate-reduction largely depended on the su pply of organic materials, i.e. the more sufficient the organic materials, the more intensive the sulfate-reduction, and therefore the lower the value of δ 13C in carbonates. When the oxic sediments were deposited on the sea floor, the remains of planktonic organisms and benthic algae were oxidized causing the release of light C-isotope from these organic materials into the bottom seawat er. Presumbly, the values of δ13C was very low in the carbonate system of the bottom seawater as long as the supply of dissolved oxygen and organic mater ials were sufficient.
Keywords:
收稿日期 2000-03-20 修回日期 2000-03-20 网络版发布日期  
DOI:
基金项目:

通讯作者:
作者简介:
作者Email:

参考文献:
本刊中的类似文章

Copyright by 高校地质学报