陈慧娴, 王建华, 董玮琛, 黄康有, 张恺, 陈子豪. 晚全新世淇澳岛红树林有孔虫记录与古环境意义[J]. 海洋地质与第四纪地质, 2020, 40(3): 74-86. DOI: 10.16562/j.cnki.0256-1492.2019031502
引用本文: 陈慧娴, 王建华, 董玮琛, 黄康有, 张恺, 陈子豪. 晚全新世淇澳岛红树林有孔虫记录与古环境意义[J]. 海洋地质与第四纪地质, 2020, 40(3): 74-86. DOI: 10.16562/j.cnki.0256-1492.2019031502
CHEN Huixian, WANG Jianhua, DONG Weichen, HUANG Kangyou, ZHANG Kai, CHEN Zihao. Late Holocene foraminiferal record from mangrove reserve, Qi’ao Island, Pearl River Estuary and its implications for paleoenvironment[J]. Marine Geology & Quaternary Geology, 2020, 40(3): 74-86. DOI: 10.16562/j.cnki.0256-1492.2019031502
Citation: CHEN Huixian, WANG Jianhua, DONG Weichen, HUANG Kangyou, ZHANG Kai, CHEN Zihao. Late Holocene foraminiferal record from mangrove reserve, Qi’ao Island, Pearl River Estuary and its implications for paleoenvironment[J]. Marine Geology & Quaternary Geology, 2020, 40(3): 74-86. DOI: 10.16562/j.cnki.0256-1492.2019031502

晚全新世淇澳岛红树林有孔虫记录与古环境意义

Late Holocene foraminiferal record from mangrove reserve, Qi’ao Island, Pearl River Estuary and its implications for paleoenvironment

  • 摘要: 潮间带有孔虫近年来被广泛地用于高精度古海平面等环境变化的研究中,但是在华南沿海此类研究少见。本文选取珠江口淇澳岛红树林潮间带上部长度为300 cm的QA钻孔进行了AMS14C测年,有孔虫、沉积物粒径、灰度分析,初步探究了研究区有孔虫作为高精度海平面指标的可能性及其所反映的古环境意义。研究结果显示钻孔包含两种有孔虫组合,一种是钙质有壳组合,常见属种为Ammonia becсarii(78.7%),Proelphidium granosum(6.6%)和Elphidiella kiangsuensis(5.6%),沉积底质为黏土质粉砂,对应沉积环境为河口潮下带;另一种是胶结壳组合,常见属种为Arenoparella mexicana(50.6%)、Miliammina fusca(17.5%)、Trochammia sp.(6.8%),沉积底质为砂质粉砂,含丰富植物碎屑,对应沉积环境为潮间带中上部红树林潮滩。结合AMS14C结果,QA钻孔记录了约4 200年以来的沉积,研究区初始为河口浅滩,由于三角洲进积作用浅滩淤积至海平面以上,约2 400年前研究区形成红树林中高潮滩。红树林沉积层中夹有两层粒度较细的钙质壳有孔虫沉积,推测可能由区域性次一级的海平面上升导致。灰度值反映了红树林沉积层中3个有机质含量较高的阶段,指示了温暖潮湿的气候,年代大约为3 000~2 700 cal. aBP, 1 200~1 100 cal. aBP, 600~500 cal. aBP,与海平面上升阶段较为接近。

     

    Abstract: Intertidal foraminifera has been widely used in paleoenvironmental reconstruction, and especially, in researches on high-resolution relative sea-level fluctuation. Unfortunately, such researches are lacking in the South China coast. This time, a long core up to 300 cm in length was retrieved from the upper intertidal zone of the mangrove on the Qi’ao Island of the Pearl River estuary. AMS14C dating, foraminifera, grain size distribution and grayscale analysis were employed to ascertain the possibility to apply the mangrove foraminifera as a high-resolution proxy for sea level fluctuation and paleoenvironmental evolution. Two foraminiferal assemblages were acquired from the core QA, a calcareous group dominated by Ammonia becсarii (78.7%), with common species Proelphidium granosum (6.6%) and Elphidiella kiangsuensis (5.6%), from a clayey slit sediment, indicating an estuarine subtidal environment; and an agglutinated assemblage dominated by Arenoparella mexicana (50.6%) with common species Miliammina fusca (17.5%), Trochammia sp. (6.8%), from a layer of sandy silt deposits with abundant plants debris and residues, indicating an upper or middle mangrove intertidal environment. AMS14C dates suggest that, the sediments formed approximately 4 200 cal. aBP, when the study area was a subtidal or mudflats environments. It turned to a middle-high mangrove at ~2 400 cal. aBP, resulted from the falling of relative sea-level caused by deltaic progradation. Two fine grained layers were intercalated in mangrove sediments, which contain calcareous foraminiferal tests corresponding to 1 022 ~ 729 cal. aBP and 508 ~ 358 cal. aBP respectively, probably related to a sub-regional sea-level rise. The grayscale suggests three phases of high humification, corresponding to ~3 000~2 700 cal. aBP, 1 200~1 100 cal. aBP, 600~500 cal. aBP respectively, indicating a warm and humid climate, which are close to the sea-level rise periods.

     

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