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珠江三角洲是中国最主要的三角洲之一,人口密集,在未来极易受到海平面上升的影响,因此该地区的海平面变化研究尤为重要。有孔虫、介形类等微体动物是半咸水中最重要的生物类群,对海平面变化非常敏感,虽然已有许多涉及研究区微体化石的研究,但该地区微体化石定量分析还未开展,详细的古环境演化过程亦有待阐明。本文利用取自珠江三角洲中部大鳌子平原的5个钻孔的岩芯进行分析,对其中PRD05和PRD04钻孔进行详细的微体动物群定量分析和宏体动物群分析,结合各钻孔沉积学及磁化率特征及其他3个钻孔测年样品的微体、宏体动物群分析,讨论了珠江三角洲中部的环境演化过程。微体动物根据已有水深分布资料,划为两种类型分别代表近岸和远岸两种类型,借以讨论海平面变化。结果显示,珠江三角洲中部晚第四纪的古环境由钻孔中从下到上7个层位的划分体现为3个沉积阶段:1)低地沉积阶段(14340cal.aB.P.前),包括基岩及其风化层(层位A),末次冰期前和期间的河流沉积环境(层位B);2)全新世海侵阶段(14340～2860cal.aB.P.),包括障壁后沉积(层位C,14340～6480cal.aB.P.)和河口湾沉积(层位D,6480～2860cal.aB.P.);3)高地沉积阶段(2860cal.aB.P.至今),包括砂坝环境(层位E,2860～230cal.aB.P.)和三角洲平原沉积(层位F,230cal.aB.P.至今)。其中全新世海侵阶段的河口湾沉积,主要由微体动物群特征反映了更高分辨率的环境演化,包括全新世伊始的快速海侵(D1亚层);海侵速率降低(D2亚层);海平面显著上升(D3亚层);海平面范围最大(D4亚层),海平面最高(约5700cal.aB.P.);海平面快速降低(D5亚层);小规模海平面波动(D6亚层)。
The Pearl River Delta is one of the most important delta in China. It is densely populated and vulnerable to the rising sea level in the future. Therefore, the study of sea level change in this area is particularly important. Microfacies such as foraminifera and ostracods are the most important biological groups in brackish water and are very sensitive to sea level changes. Although there have been many studies on microfossils in the study area, the quantitative analysis of microfossils in this area Undeveloped and detailed paleoenvironmental evolution has yet to be elucidated. In this paper, five boreholes taken from the Daliangzi plain in the central part of the Pearl River Delta are used for the analysis of the PRD05 and PRD04 boreholes in detail for the quantitative analysis of the microflora and the macro-fauna analysis. And magnetic susceptibility characteristics and other three drilling dating samples of micro-body, macro-body fauna analysis to discuss the central Pearl River Delta environment evolution process. According to the existing data of water depth distribution, the two types of microfacies are divided into two types, near-shore and far-shore respectively, in order to discuss the change of sea level. The results show that the palaeo-paleo-paleoclimate in the central part of the Pearl River Delta was divided into three sedimentary stages from bottom to top in the boreholes through the following three phases: 1) low-lying sedimentary stage (14340cal.aB.P. ago), including Bedrock and its weathering layer (horizon A), the river sedimentary environment before and during the last glacial period (horizon B); 2) the Holocene transgression stage (14340-2860 cal.aB.P.) including post-fault deposition (C, 14340 ~ 6480cal.aB.P.) And estuarine sediments (D, 6480-2860cal.aB.P); 3) the highland depositional stage (2860cal.aB.P. so far) Environment (horizon E, 2860-230 cal.aB.P.) and delta plain deposition (horizon F, 230 cal.aB.P. to date). The estuarine sediments in the Holocene transgression stage mainly reflect the higher-resolution environmental evolution from the characteristics of the microflora, including the rapid transgression (D1 sub-layer) at the beginning of Holocene and the decrease of transgression rate (D2 sub-layer ); Sea level increased significantly (D3 sublayer); Sea level range was the largest (D4 sublayer), sea level was the highest (about 5700 cal.aB.P.); Sea level decreased rapidly (D5 sublayer); Small- (D6 sublayer).