珠江三角洲中部全新世以来的微体动物群记录与古环境重建

Holocene microfaunal records in the central Pearl River Delta and implications for palaeoenvironmental changes

  • 摘要: 通过分析珠江三角洲中部钻孔沉积物的微体动物群(有孔虫和介形类)组成和分布特征,结合测年、岩性、沉积物粒度和软体动物群数据,重建了珠江三角洲中部全新世以来的古环境演化。受末次冰期影响,珠江三角洲地区暴露地表遭受风化剥蚀,普遍发育杂色黏土。随着冰后期气候回暖,海平面快速回升,海水经多个口门自南向北侵入珠江三角洲地区。南部较早接受海侵,约9010 cal.aBP海水入侵至中部地区,研究区开始发育河口湾环境,并持续至4510 cal.aBP。期间,钻孔记录的微体动物群组成和丰度特征反映了2次短周期的水体条件波动,最大水深发生于约7000~5630 cal.aBP,微体动物群的丰度达到最高值。约4510 cal.aBP以来为持续海退期,河流作用逐渐增强,发育三角洲平原环境。

     

    Abstract: Holocene palaeoenvironmental reconstruction was carried out with the data of microfauna (foraminifers and ostracods), AMS14C dating, sediment grain size distribution, and molluscs, from a borehole drilled in the central Pearl River Delta. During the last glacial maximum, the whole Pearl River mouth was exposed and suffered subaerial weathering, suggested by a layer of extensively distributed mottled clay. A rapid relative sea level rising occurred with the warming of climate during Early Holocene. The marine water intruded into the deltaic area, firstly from the eight south entrances. At about 9010 cal.aBP, marine waters arrived at the central part of the deltaic area. Since then, the study area has become an estuarine environment under water until ~4510 cal.aBP. During the transgression, there were two short-terms of environmental fluctuations recorded by microfauna. The peak of transgression occurred in the time interval from ~7000 to 5630 cal.aBP marked by the highest microfaunal abundance. Since 4510 cal.aBP, however, marine influence weakened and an alluvial plain developed in the central Pearl River Delta area.

     

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