华北寒武系芙蓉统/排碧阶、江山阶底界及其区域层型研究

Global Cambrian chronostratigraphic framework of four Series and ten Stages were released by the International Stratigraphy Commission based on the Cambrian bioevents and detailed evolution of carbon isotope composition. As a result of the GSSP's of the Cambrian Terreneuvian Series/Fortunian Stage, Drumian Stage, GuzhangianStage, as well as the Furongian Series/Paibian Stage have been ratified respectively. However, traditional Cambrian chronostratigraphic framework established on the basis of Cambrian lithostratigraphic units which are not in accordance with the global Cambrian chronostratigraphic framework still continues to be extensively used in North China. Since both palaeoenvironment and biological development in North China Plate were different from those in South China Plate in Cambrian period when they were separated and isolated, this lead to the Cambrian chronostratigraphy in North China cann't compare with that in South China. Moreover, studies on Cambrian chronostratigraphy that is consistent with the Gobal Cambrian chronostratigraphic framwork not yet started in North China. This project intends to select representative section of Cambrian system in North China to carry out a initiate study on biostratigraphy and carbon isotope stratigraphy, and to define the base of the Furongian Series/Paibian Stage and Jiangshanian Stage for classification and correlation of Cambrian chronostratigraphy in North China.

国际地层委员会根据寒武纪重要生物演化事件、碳同位素组成演化事件提出了全球寒武系“四统”、“十阶”的标准年代地层框架，并相继完成了全球寒武系Terreneuvian统/Fortunian阶、第三统Drumian阶、古丈阶、芙蓉统/排碧阶、江山阶GSSP的建立，为全球寒武系年代地层的对比提供了标准，但是基于岩石地层单位建立的传统寒武系年代地层框架目前仍继续在我国华北地区广泛使用。由于寒武纪时期，我国华北、华南地区是相互独立的陆块，古地理差异较大、生物发育不同，两区寒武纪年代地层精准对比比较困难，况且我国华北地区与全球寒武系年代地层接轨的研究尚没有起步。本项目拟在华北地区选择代表性寒武系地层剖面开展初步的生物地层和碳同位素地层研究工作，在与全球寒武系芙蓉统/排碧阶、江山阶“金钉子”剖面对比的基础上，初步确定华北地区寒武系芙蓉统/排碧阶、江山阶底界，为我国南、北寒武系年代地层精准对比提供基础地质资料。

国际地层委员会寒武系分会提出了4统10阶寒武系地层划分新方案，在北美及我国华南地区建立了全球寒武系纽芬兰统幸运阶、第三统鼓山阶、古丈阶、芙蓉统排碧阶、江山阶的标准层型剖面和点（GSSP）。我国华北地区寒武系经过100多年的研究，建立了下、中、上三统的地层划分方案，以华北寒武系为基础建立的岩石地层单位、年代地层单位、生物地层单位曾作为我国南北寒武系地层划分与对比的依据。在全球寒武系4统10阶的新地层系统确立之后，我国华北地区寒武系年代地层系统该如何精准与其对接，是今后我国寒武系研究的一个新方向。本项目选定华北寒武系芙蓉统排碧阶、江山阶底界作为研究目标，对山东长清唐王寨剖面、河南卫辉塔岗水库剖、西岭后剖面开展寒武系岩石地层、生物地层、层序地层、化学地层研究，在传统寒武系长山阶的底部发现显著的碳同位素组成正漂移（西岭后剖面δ13C达到 3.5‰，唐王寨剖面δ13C达到 1.8‰），正漂移的起始位置接近三叶虫Chungia的首现位置，从而定义了华北寒武系寒武系芙蓉统排碧阶的底界。并首次对芙蓉统排碧阶开展微量元素、稀土元素的分布特征研究，发现长山阶下部的微量元素V、Cr、Sc、Ti、Hf、Th、Cs、Ta、Nb、Zr、Rb、Zn、Cu、Ni、Co和稀土元素Y、Lu、Yb、Tm、Er、Ho、Dy、Tb、Gd、Eu、Sm、Nd、Pr、Ce、La分布均表现为正异常，是背景值的3-6倍，可作为寒武系芙蓉统排碧阶确定的又一重要标志。