Abstract—

The biostratigraphy of the lower boundaries of the Atdabanian Stage of the General Stratigraphic Scale of Russia and Stage 3 of the International Chronostratigraphic Chart is discussed. It is generally accepted that the first appearance of trilobites is the main characteristic of these stages. The difficulties in selecting the correlation level for the lower boundary of Stage 3 on the basis of trilobites are explained by the different taxonomic compositions of the assemblages of the most ancient representatives of this arthropod group on different paleocontinents and evident diachronism of the levels of their first appearance. For these purposes, it is proposed to use the species Mobergella radiolata Bengtson, 1968, the geographical distribution of which is wider than that of any species of ancient trilobites. It was shown that in the stratotype region of the Lower Cambrian stages in the Siberian Platform (the interfluve between the Lena and Aldan rivers), M. radiolata appears in sections at the same level as the first Atdabanian archaeocyaths of the Retecoscinus zegebarti Zone. This allows M. radiolata to be used as an index species for the base of the Atdabanian. Finds of M. radiolata in other regions of the Siberian Platform (west, north, and southeast, interior areas of the platform) make this microfossil an extremely valuable tool for biostratigraphy of the Lower Cambrian, with a much higher correlation potential than locally common early Atdabanian archaeocyaths or trilobites.

中文翻译：

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有问题的化石Mobergella radiolata作为下寒武纪的索引物种

摘要—

讨论了俄罗斯一般地层规模的阿达巴尼亚阶和国际时间地层图的第三阶段下界的生物地层。通常认为三叶虫的首次出现是这些阶段的主要特征。在三叶虫的基础上为第三阶段的下边界选择相关水平的困难是由于该节肢动物群中最古老的代表在不同的古大陆上的组合的不同分类学组成以及它们的第一水平的明显历时性所造成的。出现。出于这些目的，建议使用Mobergella radiolata种Bengtson，1968年，其地理分布范围比任何古代三叶虫物种的地理分布范围都广。结果表明，在西伯利亚平台下寒武纪的地层型区域（Lena河和Aldan河之间的交汇处），M。radiolata出现在与Retecoscinus zegebarti区域的第一个Atdabanian考古遗址相同的剖面上。这使得辐射松分枝杆菌可以用作阿达巴尼亚人基地的索引物种。的认定M. radiolata 在西伯利亚平台的其他地区（该平台的西部，北部和东南部内部区域），使得该微化石成为下寒武统生物地层学的极有价值工具，其相关潜力远高于当地常见的早期阿达巴尼亚古考古遗址或三叶虫。