CHARACTERISTICS OF THE FORAMINIFERAL TAPHOCOENOSE IN THE NORTHEAST BOHAI AND RELATIONSHIP TO THE SEDIMENTARY ENVIRONMENT

Based on the quantitative and qualitative analysis of 211 surface sediment samples in the northeast Bohai, 109 benthic foraminifera species which belong to 48 genera were recognized. Very few planktonic foraminifera were found in this studied area. Q-mode factor analysis was made for the 58 benthic foraminifera species, and 3 varimax factors with a cumulative contribution of 98.62% have been revealed as follows:AssemblageⅠ(Ammonia beccrii vars.-Buccella frigida), which represents a littoral environment with low-temperature and low-salinity alongshore currents; AssemblageⅡ(Nonion anomalinoidea-Eggerella sp.), which represents a nearshore shallow-sea environment with distributions of fine sand and clay; Assemblage Ⅲ (Ammonia compressiuscula-Buccella tunicate), which indicates shallow-sea environment of more than 30 m water depth. The distribution of foraminiferal taphocoenose in the study area is mainly controlled by such factors as alongshore currents typical of low temperature and low salinity in winter season, sediment types, tidal currents, sedimentation rates, and CaCO₃ contents.