长江远端三角洲表层沉积物中底栖有孔虫分布及其对环境的指示

Distribution of benthic forminifera in the surficial sediments of Changjiang distal delta and its environmental implications

  • 摘要: 长江远端三角洲是东海内陆架泥质沉积体重要组成部分,是全新世高海平面时期以来形成的重要地貌单元,其包含了高分辨率沉积环境与气候变化信息,对该地区现代沉积环境及其影响条件的分析将有助于长时间尺度古记录识别与反演。对研究区海域145个站位的表层沉积物样品进行了底栖有孔虫化石分析,鉴定结果表明该地区底栖有孔虫有52种,以玻璃壳体类型为主,平均含量占底栖有孔虫总量的90.6 %,其次为瓷质壳,胶结壳含量最低。进一步因子分析结果表明,研究区底栖有孔虫可划分为4个组合:组合Ⅰ(Ammonia beccarii vars.-Quinqueloculina spp.)分布在研究区西部近岸浅水区,组合Ⅱ(Bolivina robusta-Bulimina marginata-Hanzawaia spp.)分布于研究区东南部水深较大处,组合Ⅲ(Elphidium hispidulum-Fursenkoina schreibersiana)呈带状分布于近岸,组合Ⅳ(Elphidium advenum-Ammonia pauciloculata)分布区域位于组合Ⅰ和组合Ⅱ之间。组合Ⅰ可能指示区域水体环境受闽浙沿岸水团影响;组合Ⅱ可能指示区域水体环境受台湾暖流水团影响;组合Ⅲ的分布可能与夏季闽江水与外海水混合发生水体层化有关;组合Ⅳ可能指示区域水体环境受季节性闽浙沿岸水与台湾暖流水团影响。

     

    Abstract: The distal end of the Yangtze River delta, as a part of the muddy sediments on the continental shelf of the East China Sea, is formed right after the high sea level of Holocene and contains high-resolution information of environmental and climatic changes. In order to make better interpretation of the long-term paleoenvironmental records, 145 surface samples collected from the northern coastal waters of Fujian Province have been quantitatively analyzed for foraminifera distribution. 52 species of benthonic foraminifera were identified dominated by hyaline Rotaliida, followed successively by porcelaneous Miliolina, and agglutinated Textulariida. Four assemblages have been recognizeded based on factor analysis: The Assemblage I (Ammonia beccarii vars. -Quinqueloculina spp.) is mainly distributed in the shallow-water environment possibly related to the Minzhe coastal current; The Assemblage II (Bolivina robusta-Bulimina marginata-Hanzawaia spp.) indicates the environment predominated by the warm current coming from Taiwan; The Assemblage III (Elphidium hispidulum-Fursenkoina schreibersiana) is distributed in a ribbon pattern near the shore, where the water from the Minjiang River is stratified with sea water in summer; The Assemblage IV (Elphidium advenum-Ammonia pauciloculata) is restricted in some local areas between the Assemblage I and II, possibly indicating an environment dominated by mixed water mass. The research results suggest that the combination and distribution of benthic foraminifera in the study area are not only affected by material source, but also constrained by their dynamic environment, which is of great significance to the reconstruction of paleoenvironment in the areas as such.

     

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