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

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.