阎琨,庞国涛,邢新丽,等. 广西三娘湾准残留沉积——来自端元分析和稀土元素地球化学的证据[J]. 海洋地质前沿,2023,39(9):25-34. DOI: 10.16028/j.1009-2722.2022.095
    引用本文: 阎琨,庞国涛,邢新丽,等. 广西三娘湾准残留沉积——来自端元分析和稀土元素地球化学的证据[J]. 海洋地质前沿,2023,39(9):25-34. DOI: 10.16028/j.1009-2722.2022.095
    YAN Kun, PANG Guotao, XING Xinli, et al. Palimpsest sediments in Sanniang Bay, Guangxi: evidence from end-member and rare earth elements[J]. Marine Geology Frontiers, 2023, 39(9): 25-34. DOI: 10.16028/j.1009-2722.2022.095
    Citation: YAN Kun, PANG Guotao, XING Xinli, et al. Palimpsest sediments in Sanniang Bay, Guangxi: evidence from end-member and rare earth elements[J]. Marine Geology Frontiers, 2023, 39(9): 25-34. DOI: 10.16028/j.1009-2722.2022.095

    广西三娘湾准残留沉积

    Palimpsest sediments in Sanniang Bay, Guangxi: evidence from end-member and rare earth elements

    • 摘要: 残留沉积能够记录海进海退的关键信息,也是恢复古地理的有力证据。在2019年10月的海洋地质调查中,在三娘湾海域>10 m水深区域识别出一套含砾的沉积物。在粒度分析和地球化学测试的基础上,利用端元分析模型和稀土元素判别图解分析其形成原因及物质来源。结果表明,三娘湾沉积物的信息可以由4个端元(EM)来表示,EM1代表了钦州湾往复潮流的特征,EM2为大风江河口高能的冲刷环境,EM3代表了残留沉积与波浪的混合作用,EM4代表了残留沉积的原始河流沉积。稀土元素特征表明,残留沉积具有低稀土总量、高ΣLREE/ΣHREE的特点。经过上地壳稀土元素标准化后,显示出明显的δCe正异常和δEu负异常,表现出砂页岩、砂岩来源的特征,与钦州湾东北部的近岸沉积具有相似的特征。综合分析表明,三娘湾准残留沉积是北部湾地区最后一次大规模海进的残留产物,受到海流和潮流的后期改造,这为北部湾地区古海岸线识别和演化研究,提供了关键信息。

       

      Abstract: Relict sediments record the key information of transgression and regression, and it is also a powerful evidence for the reconstruction of paleogeography. In the marine geological survey in October 2019, a set of gravelly sediments was collected in the area in more than 10 m depth in the Sanniang Bay , Qinzhou, Guangxi. To understand the causes of formation and provenance, grain size analysis and geochemical test were conducted, and the end-member analysis model and rare earth element discrimination diagram were used. The information of Sanniang Bay sediment could be characterized by four end-member (EM). EM1 represents the characteristics of reciprocating tidal current in Qinzhou Bay, EM2 is the high-energy scouring environment of Dafeng River estuary, EM3 reflects the mixing action of relict sediments and wave, and EM4 signifies the original river deposition of relict sediments. The characteristics of rare earth elements (REE) show that the relict sediments has the characteristics of low ΣREE and high ΣLREE/ΣHREE. After the normalization of REE to the upper crust, it shows obvious δCe positive anomaly and δEu negative anomaly, which indicates the characteristics of the source of sand shale and sandstone. It is similar to the nearshore sedimentation in the northeast of Qinzhou Bay. Our comprehensive analysis showed that the palimpsest sediments in the Sanniang Bay is the relict product of the latest large-scale transgression in the Beibu Gulf, and is transformed by ocean current and tide. The result provides key information for the identification and evolution of ancient coastline in the Beibu Gulf.

       

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