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Taphonomic pathway of exceptionally preserved fossils in the Lower Ordovician of Morocco
Geobios ( IF 1.6 ) Pub Date : 2020-06-01 , DOI: 10.1016/j.geobios.2020.04.001
Farid Saleh , Bernard Pittet , Pierre Sansjofre , Pierre Guériau , Stefan Lalonde , Jean-Philippe Perrillat , Muriel Vidal , Victoire Lucas , Khadija El Hariri , Khaoula Kouraiss , Bertrand Lefebvre

Abstract The Fezouata Shale in Morocco is the only Lower Ordovician Lagerstatte to yield a diverse exceptionally preserved marine fauna. Sediments of this formation have yielded soft to lightly sclerotized taxa that were previously unknown from the Ordovician. Yet the taphonomic pathway of fossils from this formation remains poorly understood. Here, based on drill core material, a close association between exceptional preservation and a specific sedimentary facies is evidenced in the Fezouata Shale. This facies corresponds to calm sea-bottoms, sporadically smothered by distal storm deposits. The patterns of exceptional preservation in this facies indicate that most animals were dead and decayed on the seafloor prior to their burial by distal storm deposits. Furthermore, contrasted elemental and molecular compositions between fresh-cored and altered materials show that surface deposits of the Fezouata Shale were substantially affected by recent weathering. This weathering resulted in the leaching of organic materials from fossils originally preserved as carbonaceous compressions and the transformation of pyrite into iron oxides. Understanding the processes behind the current patterns of soft tissue preservation in the Fezouata Shale is essential prior to any palaeontological description, especially of taxa with no current representatives.

中文翻译:

摩洛哥下奥陶统保存完好的化石的埋藏途径

摘要 摩洛哥的 Fezouata 页岩是唯一一个下奥陶统 Lagerstatte 产生多样化的、保存完好的海洋动物群。这个地层的沉积物产生了以前从奥陶纪未知的软到轻微硬化的分类群。然而,人们对这种地层化石的埋藏途径仍知之甚少。在这里,基于钻芯材料,在 Fezouata 页岩中证明了特殊保存与特定沉积相之间的密切关联。该相对应于平静的海底,偶尔被远端风暴沉积物淹没。该相中异常保存的模式表明,大多数动物在被远端风暴沉积物掩埋之前已经死亡并在海底腐烂。此外,新鲜岩心和蚀变材料之间的元素和分子组成对比表明,Fezouata 页岩的表面沉积物受到近期风化作用的显着影响。这种风化导致有机材料从最初保存为碳质压缩物的化石中浸出,并将黄铁矿转化为氧化铁。在进行任何古生物学描述之前,了解 Fezouata 页岩中当前软组织保存模式背后的过程是必不可少的,尤其是对于目前没有代表的分类群。这种风化导致有机材料从最初保存为碳质压缩物的化石中浸出,并将黄铁矿转化为氧化铁。在进行任何古生物学描述之前,了解 Fezouata 页岩中当前软组织保存模式背后的过程是必不可少的,尤其是对于目前没有代表的分类群。这种风化导致有机材料从最初保存为碳质压缩物的化石中浸出,并将黄铁矿转化为氧化铁。在进行任何古生物学描述之前,了解 Fezouata 页岩中当前软组织保存模式背后的过程是必不可少的,尤其是对于目前没有代表的分类群。
更新日期:2020-06-01
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