New U–Pb radioisotopic ages on early Cambrian volcanic zircons condition a high-resolution Bayesian age model that constrains the first occurrences and zonations of West Gondwanan archaeocyaths and trilobites in southern Morocco. The oldest archaeocyaths in the Tiout Member of the Igoudine Formation (519.71 + 0.26/− 0.35 Ma) are c. 6 Ma younger than the oldest Siberian archaeocyaths. The oldest Moroccan trilobite fragments, from the lower member of the Igoudine, are constrained to 519.95 + 0.43/− 0.40 Ma. The succeeding Issendalenian Stage (i.e. Hupetina antique – Eofallotaspis tioutensis – Fallotaspis plana – Choubertella – Daguinaspis trilobite zones) spans c. 1.5 Ma (519.78 + 0.26/− 0.37 Ma to 518.43 + 0.25/− 0.69 Ma). Identifiable Moroccan fallotaspidids and bigotinids, among Earth’s oldest trilobites, occur above a positive δ13C excursion dated with our age model at 520.27 + 0.59/− 0.57 Ma, and correlated with the IV excursion peak within the lower range of Siberian Atdabanian Stage trilobites (Repinaella Zone). This excursion is the best standard for a Cambrian Series 2 base. The oldest West Gondwana trilobite fragments are c. 1 Ma younger than those in Siberia and c. 0.5 Ma older than the oldest Avalonian trilobites (Callavia Zone). This diachrony means a trilobite first appearance datum is an inappropriate chronostratigraphic base for Cambrian Series 2. Taxonomic differences in the oldest trilobites between Cambrian palaeocontinents are in accordance with trace fossil evidence for the group’s appearance possibly as late as c. 530 Ma in the Cambrian Evolutionary Radiation. Coeval 519–517 Ma dates from Avalonia (cool-water siliciclastic shelf) and West Gondwana (tropical carbonate platform) sections with distinct macrofaunas emphasize these successions were latitudinally separate by the late Ediacaran Period.

中文翻译：

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精确的早寒武纪 U-Pb 锆石日期包含摩洛哥西部冈瓦纳最古老的三叶虫和古细菌

早寒武世火山锆石的新 U-Pb 放射性同位素年龄为高分辨率贝叶斯年龄模型提供了条件，该模型限制了摩洛哥南部西冈瓦南古菌和三叶虫的首次出现和分带。Igoudine 组 Tiout 段中最古老的古菌 (519.71 + 0.26/− 0.35 Ma) 是C。比最古老的西伯利亚古树年轻6 Ma。来自伊古丁下段的最古老的摩洛哥三叶虫碎片被限制在 519.95 + 0.43/- 0.40 Ma。随后的伊森达伦阶段（即胡佩蒂娜古董–Eofallotaspis tioutensis – Fallotaspis plana – Choubertella – Daguinaspis三叶虫区）跨度C。1.5 Ma（519.78 + 0.26/- 0.37 Ma 到 518.43 + 0.25/- 0.69 Ma）。在地球上最古老的三叶虫中，可识别的摩洛哥法罗塔斯皮德和比戈丁斯发生在正δ以上13C 偏移与我们的年龄模型在 520.27 + 0.59/− 0.57 Ma 约会，并与 IV 偏移峰值相关之内西伯利亚阿达巴阶三叶虫的下界（雷皮纳拉区）。这次游览是寒武纪系列 2 基地的最佳标准。最古老的西冈瓦纳三叶虫碎片是C。比西伯利亚小1马C。比最古老的阿瓦隆纪三叶虫早 0.5 Ma（卡拉维亚区）。这种历时性意味着三叶虫首次出现的数据不是寒武纪系列 2 的不合适的年代地层学基础。寒武纪古大陆之间最古老三叶虫的分类学差异与该组出现的痕迹化石证据一致，可能晚于C。530 Ma 中的寒武纪演化辐射。来自 Avalonia（冷水硅质碎屑陆架）和西冈瓦纳（热带碳酸盐台地）剖面的 Coeval 519-517 Ma 具有不同的大型动物群，强调这些演替在埃迪卡拉纪晚期在纬度上是分开的。