齐晓婕, 黄宝琦, 秦亚超, 刘嘉栋. 苏北LYK钻孔千年以来的沉积记录及古环境演化[J]. 海洋地质与第四纪地质, 2021, 41(3): 33-43. DOI: 10.16562/j.cnki.0256-1492.2020091901
引用本文: 齐晓婕, 黄宝琦, 秦亚超, 刘嘉栋. 苏北LYK钻孔千年以来的沉积记录及古环境演化[J]. 海洋地质与第四纪地质, 2021, 41(3): 33-43. DOI: 10.16562/j.cnki.0256-1492.2020091901
QI Xiaojie, HUANG Baoqi, QIN Yachao, LIU Jiadong. Sedimentary records and paleo-environmental evolution of core LYK in northern Jiangsu province for a thousand of year.[J]. Marine Geology & Quaternary Geology, 2021, 41(3): 33-43. DOI: 10.16562/j.cnki.0256-1492.2020091901
Citation: QI Xiaojie, HUANG Baoqi, QIN Yachao, LIU Jiadong. Sedimentary records and paleo-environmental evolution of core LYK in northern Jiangsu province for a thousand of year.[J]. Marine Geology & Quaternary Geology, 2021, 41(3): 33-43. DOI: 10.16562/j.cnki.0256-1492.2020091901

苏北LYK钻孔千年以来的沉积记录及古环境演化

Sedimentary records and paleo-environmental evolution of core LYK in northern Jiangsu province for a thousand of year.

  • 摘要: 对废黄河水下三角洲北翼LYK钻孔微体生物群的分布特征及属种组合进行研究,共鉴定底栖有孔虫50属67种,介形类30属46种,运用Q型聚类分析,将钻孔内底栖有孔虫划分为5个组合,并结合AMS14C测年结果和沉积物粒度特征,恢复了研究区域千年以来的沉积环境演化:在黄河流入前,研究区发育粒度较细、分选较好的陆架沉积,微体生物群组合接近正常海相;在黄河夺淮入海后,研究区开始接受巨量的粗颗粒沉积物,分选变差,出现了大量近岸半咸水属种的有孔虫和介形虫,沉积环境从典型的浅海向三角洲前缘演变;直到黄河北归后,大量泥沙供给断绝,在波浪和潮流的共同作用下,研究区经历了侵蚀和再沉积过程,沉积物砂泥比升高,微体生物群丰度和分异度急剧下降,广盐类微体生物群增加;随着侵蚀中心逐渐南移,研究区动力条件趋于稳定,前期形成的侵蚀洼地逐渐接受径流和潮流的双向沉积,出现大量浮游有孔虫等异地分子;近年来,伴随波浪和潮汐的改造加工,研究区逐渐形成了趋于平缓的夷平面,由动荡的滨岸逐渐过渡到现今稳定的浅海相沉积环境。

     

    Abstract: Quantitative study of micropaleontology is carried out for the core LYK drilled at the northern part of the abandoned Yellow River delta. 106 benthic foraminiferal species of 68 genera and 46 ostracod species of 30 genera are discovered. By Q-mode hierarchical cluster analysis, the foraminifera found can be divided into five assemblages. AMS14C dating and grain size data are adopted to reconstruct the environmental evolution over the past millennia. The results suggest that the study area was dominated by fine-grained and well-sorted shelf sediments and the microbiota assemblage was close to normal marine facies before the Yellow River poured into the sea. The study area started receiving enormous coarse-grained sediments with worse sorting after the Yellow River seized the Huaihe river channel and entered the sea. There appeared a large number of foraminifers and ostracods of nearshore brackish water genus, and the sedimentary environment was changed from a typical shallow sea to a delta-front. Once the Yellow River moved to the north, large sediment supply was cut off. Under the joint action of waves and tidal currents, the study area was suffered from erosion and redeposition, and the sand/mud ratio was thus increased. The abundance and diversity of microbiota declined sharply, while the wide salinity microbiota increased. With the gradual southward movement of the erosional center, the dynamic conditions of the study area became stabilized. The erosional depressions formed in the early stage gradually accepted sediments from both the runoff and tidal current, and a large number of floating foraminifers and off-site molecules appeared. In recent years, along with the reworking of waves and tides, the study area gradually becomes flatter and changes from a turbulent shoreline to a stable shallow sea.

     

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