Abstract The index ichnofossil Treptichnus pedum Seilacher1955 and four types of Microbially Induced Sedimentary Structures (MISS) - variants of wrinkle and elephant skin structures – are the first fossils described from the Tres Marias Formation, topmost unit of the Bambui Group of south-central Brazil. Despite the stratigraphic importance and widespread occurrence of this unit in the Sao Francisco Craton and adjacent Brasilia Fold Belt, its age is still poorly constrained between the Neoproterozoic and Early Paleozoic. This discovery is significant because the first appearance datum (FAD) of T. pedum has been used to define the Ediacaran-Cambrian boundary. Hence, the presence of T. pedum indicates an early Paleozoic age for the uppermost Bambui Group and means that the Ediacaran-Cambrian limit must lie deeper in the Bambui Group, somewhere between this level and that of the terminal Ediacaran index-fossil Cloudina sp. in the Sete Lagoas Formation, near the base of the group. Available age determinations on detrital zircon grains and chemostratigraphic correlations are consistent with an Ediacaran to Cambrian age for this group. Detailed paleontological prospection throughout the group may now proceed within a better constrained time frame and hopefully reveal additional fossil evidence of Cambrian as well as Ediacaran life in the Bambui Group.

中文翻译：

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巴西中南部 Três Marias 组中的 Treptichnus pedum 及其对南美洲埃迪卡拉纪-寒武纪过渡的影响

摘要 索引 ichnofossil Treeptichnus pedum Seilacher 1955 和四种微生物诱导沉积结构 (MISS) - 皱纹和象皮结构的变体 - 是从 Tres Marias 组描述的第一批化石，Tres Marias 组是巴西中南部 Bambui 群的最顶层单元。尽管该单元在圣弗朗西斯科克拉通和邻近的巴西利亚褶皱带具有重要的地层重要性和广泛分布，但其年龄在新元古代和早古生代之间仍然缺乏约束。这一发现意义重大，因为 T. pedum 的首次出现基准 (FAD) 已被用于定义埃迪卡拉纪-寒武纪边界。因此，T. pedum 的存在表明最上层 Bambui 群的早古生代时代，意味着 Ediacaran-Cambrian 界限必须位于 Bambui 群的更深处，介于这个水平和埃迪卡拉纪末期指数化石 Cloudina sp 之间的某个水平。在 Sete Lagoas 组中，靠近该组的底部。碎屑锆石颗粒的可用年龄测定和化学地层相关性与该组的埃迪卡拉纪至寒武纪年龄一致。整个小组的详细古生物学勘探现在可能会在一个更好的受限时间范围内进行，并有望揭示 Bambui 群中寒武纪和埃迪卡拉纪生命的更多化石证据。