晚第四纪热带西太平洋Noelaerhabdaceae科颗石长度和质量变化及其影响因素

Variations in the length and weight of Noelaerhabdaceae coccolith in the Late Quaternary tropical Western Pacific and their influencing factors

  • 摘要: 选取热带西太平洋暖池北部边缘西菲律宾海本哈姆高原(Benham Rise)MD06-3050站位的柱状样沉积物样品,利用双向圆偏光法拍摄并合成图像,通过SYRACO人工智能软件自动识别并测量和计算Noelaerhabdaceae科颗石的平均长度和平均质量。研究结果显示,自35万年以来,Noelaerhabdaceae科平均颗石长度和质量的变化趋势具有较强的相似性,两者的冰期/间冰期变化特征均不明显。根据颗石长度和质量计算得到的颗石钙化作用指标曲线与前两者的变化趋势也存在一定的相似性,说明研究海区颗石的平均质量和长度均可作为指示颗石藻钙化作用程度的指标。通过与冰芯记录的大气pCO2变化曲线进行对比,发现在大气pCO2浓度较高的冰期终止期以及间冰期早期,该科颗石的钙化作用相对较低,表明pCO2在一定程度上影响了颗石藻的钙化作用。此外,对颗石的平均长度和质量进行23 ka周期滤波,两滤波曲线的变化与北纬15°夏季平均日照辐射曲线的变化较为一致,指示了地球天文轨道参数对颗石藻演化的调控作用。

     

    Abstract: Sediment samples from core MD06-3050 in the Benham Rise in the Western Philippine Sea at the northern edge of the tropical Western Pacific Warm Pool were selected for Family Noelaerhabdaceae coccolith size analyses. Images were taken and synthesized using bidirectional circular polarization method. The average coccolith length and weight were automatically identified and measured by SYRACO artificial intelligence software. Results show that the average coccolith length and weight show strong similarities in the last 350000 years, with no obvious glacial-interglacial changes. The coccolith calcification index was estimated based on the length and weight of coccolith, and shows the same patterns of the morphological parameters, but presents a more obvious glacial-interglacial pattern. The coccolith calcification index was compared with the ice-core atmospheric pCO2, which shows that the calcification of Noelaerhabdaceae coccoliths was weakened in the glaciation termination period and the early-middle interglacial periods when the atmospheric pCO2 concentration was higher. The 23-ka filtering of the average coccolith length and weight agrees with the summer average solar radiation at 15°N, suggesting the regulation of the Earth's astronomical orbit parameters on the evolution of coccolithophores.

     

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