Abstract This article presents complex paleo-pedoturbation features, preserved in a massive mudstone stratum belonging to a siliciclastic sequence in the upper Eocene. The outcrop of these turbations presents an intricate network of iron oxide in semi tubular forms. The mudstone to which these structures are restricted is lithologically similar to other mudstone beds, below and above it in the sequence. In contrast, it presents more paleo-pedogenic features. Attributing these tubular structures to a specific burrow is difficult for two reasons: the apparent similarities in morphology to numerous trace fossils coupled with the absence of diagnostic excavation-locomotion proxies, as well as the lack of any faunal or floral body fossils in the parent mudstone. Moreover, these structures do not convincingly conform to the simplified image documented in numerous publications for fossil roots. Taking into account the exclusive, physicochemical properties of the clay rich rocks (shrink-swell behaviour, erratic permeability and cation-exchange capacity), this article provides potential evidence that such trace fossil-like features could, alternatively, be produced by abiotic redox processes without pre-existing faunal or floral predecessors. Regardless of the extent to which the provided justifications are acceptable, they might increase awareness as to just how treacherous trace fossil identification can be. The studied case draws attention to the fact that, in mudstones, the dividing line between valid and spurious trace fossils can be very subtle. It also assists in better recognition of paleosol features in mudstones.

中文翻译：

---

泥岩的物理结构在创造像氧化还原特征这样的微量化石方面的力量，始新世晚期的案例研究，锡尔特盆地

摘要 本文介绍了复杂的古土壤扰动特征，保存在属于上始新世硅质碎屑层序的块状泥岩地层中。这些扰动的露头呈现出复杂的半管状氧化铁网络。这些构造所受限制的泥岩在岩性上与其他泥岩层相似，在序列中位于其下方和上方。相比之下，它呈现出更多的古土壤特征。将这些管状结构归因于特定的洞穴很困难，原因有两个：形态学上与众多痕迹化石明显相似，加上缺乏诊断性挖掘-移动代理，以及母泥岩中缺乏任何动物或植物体化石. 而且，这些结构并不能令人信服地符合许多化石根出版物中记录的简化图像。考虑到富含粘土的岩石的独有的物理化学特性（收缩膨胀行为、不稳定的渗透性和阳离子交换能力），本文提供了潜在的证据，表明此类微量化石样特征可以由非生物氧化还原过程产生没有预先存在的动物或植物祖先。不管所提供的理由在多大程度上是可以接受的，它们可能会提高人们对痕迹化石识别的危险程度的认识。所研究的案例提请注意这样一个事实，即在泥岩中，有效和虚假痕迹化石之间的分界线可能非常微妙。