中文摘要：

珠江三角洲是主要由西江、北江和东江在珠江口湾内堆积而成的复合三角洲，自晚更新世开始形成。微体生物是珠江河口三角洲晚第四纪沉积记录中的重要组分，是重建第四纪环境变化极为有效的指标。本文样品取自PD孔岩心，钻孔位于珠江三角洲中部（113°28′35″E，22°53′41″N），孔深16．7m。代表约25100年以来的沉积。PD孔中见有孔虫6属10种，其中以Ammonia beccarii为优势种。根据地层分布特征，可识别3个有孔虫层位。介形类共7属9种，丰度较低，以Sinocytheridea impressa和Neomonoceratina delicata为代表，在5个层位相对富集。根据微体生物分布特征，并结合有机碳、氮以及磁化率数据，PD孔晚第四纪沉积可划分为6个沉积环境阶段。A．三角洲前缘阶段（-16．7～-13．5m；25100～24000aB．P．）：岩性为粗砂、砂至砂质粉砂。主要含Ammonia属的4个种（A．beccarii、A．sp．、A．tepida、A．annectens），丰度均较低，其中Ammonia beccarii为优势种。不见适应于正常浅海的Elphidium属。介形类以滨岸类型Sinocytheridea impressa为主。出现少量双壳类。代表河口附近水深10m以内软泥底质、受河流影响大、水体动荡的半咸水环境。有机碳含量和磁化率较低，同样指示低海平面时期的沉积。B．河口湾阶段（-13．5～-10．6m；24000～22400aB．P．）：岩性为粘土质粉砂至粘土。前一阶段出现的Ammonia 4个种的丰度比较高，且出现浅海底栖分子毋沲西啪advenum和Ehispidulum，以及浮游有孔虫分子Globigerinoides sp．。介形类出现Bicornucythere leizhouensis、B．bisanensis、Alocopocythere goujoni、Pistocythereis bradyformis等适应水深较大的分子，而滨岸浅水分子较少。有机碳含量和磁化率相对升高。代表海平面相对较高时期的沉积。C．三角洲平原阶段（-10．6～-9．2m；22400—21700aB．P．）：底部为一薄层花斑状风化粘

英文摘要：

Late Quaternary core sediments from the middle area of the Pearl River Delta can be lithologically divided into six units. Unit 1, 2, and 5 contain foraminifers and ostracods in different abundances. Faunal analysis suggests that they were deposited in brackish to marine environments. Unit 3 does not contain any fossils except plant debris, indicating a fluvial plain environment. Unit 4, characterized by a layer of mottled clay that is widely distributed in the Pearl River Delta area, is completely barren of fossils, representing an interval of continental weathering. Unit 6 bears only non-marine ostra- eods and was deposited on a fluvial plain. Combining foraminiferal and ostracod data with geochemical and susceptibility records allows to establish the following environmental stages in this area： A. Delta front stage （25 100 -24 000 aB. P. ） ; B. estuary stage （24 000 -22 400 aB. P. ） ; C. fluvial plain stage （22 400 -21 700 aB. P. ） ; D. continental weathering stage （21 700 -3 700 aB. P. ） ; E. tidal flat stage （3 700 N 2 600 aB. P. ） , and F. upper fluvial plain stage （ since 2 600 aB. P. ）. In the Late Quaternary sedimentary succession two transgression-regression cycles can be recognized in the study area, corresponding to stages A to D and E to F, respectively. The palaeoenvironmental changes are believed to have been controlled by fluctuations of sea level.