浙江钱塘江冰后期有孔虫化石记录及其古环境意义

本研究对浙江萧山SE2钻孔近50m沉积物岩心进行了详细的有孔虫定量统计分析,并结合测年资料重建了冰后期以来钱塘江沉积河谷的环境演化过程。有孔虫群落特征反映的古环境变化与沉积相分析结果一致。有孔虫资料显示:大约1万年以来该地区受到海水的影响、以胶结质壳Textularia-Reophax组合为特征,并在中全新世海水深度到达最大、以近岸浅水组合Ammonia beccarii-Elphidium magellanicum为代表,而晚全新世以来在全球海平面下降的影响下、该地区海水变浅的同时,却由于狭窄的特殊河口地形,水动力相对较强,显示强潮型河口地区特有的近岸分子Ammonia beccarii,Elphidium advenum和相对较深水分子Ammonia compressiuscula共存的底栖有孔虫群落特征。

POST-GLACIAL FORAMINIFERAL RECORD OF THE SOUTHERN QIANTANG RIVER ESTUARY AND ITS PALEOENVIRONMENTAL IMPLICATIONS

A 50 m sedimentary core(SE2) from Xiaoshan,southern Qiantang River estuary was taken for the study of paleoenvironmental changes.Quantitative foraminiferal analyses were performed for more than 90 samples.AMS14C dates indicate that the foraminiferal fauna records the post-glacial environmental evolution of the Qiantang River valley.With the global sea-level rise,the valley was affected by the marine water since 10 kaBP,but only few species first occurred,such as the agglutinated Textularia spp.and Reophax donghaiensis,and euryhaline Ammonia becca-rii in a lower abundance,possibly from the low-salinity intertidal zone.Both the benthic and planktic foraminifera then increased to a higher abundance and diversity during the middle Holocene,with Ammonia beccarii and Elphidium magellanicum as dominant species,which suggests coastal shallow water.However,the late Holocene foramini-feral assemblage was characterized by the nearshore Ammonia beccarii and Elphidium advenum mixed with the relatively deeper-water species Ammonia compressiuscula,which implies a shallow but high-energy water influence,possibly resulted from the narrowing estuary with the global sea-level drop,which performs as a macro-tidal estuary environment today.