Abstract The Messinian diatomaceous deposits are widely exposed in the Lower Chelif Basin (NW-Algeria). The upper part of the Diatomaceous Formation is intercalated by four diatomaceous beds rich in Zoophycos and Chondrites. Both these traces were produced by the members of endo-benthonic fauna adapted to nutrient exploitation within sediments. In the Diatomaceous Formation, larger dark-coloured Chondrites targionii cross-cuts smaller C. intricatus, which could indicate ecological succession perhaps due to conditions getting less oxygenated and causing the need for larger burrows. Size increase of Zoophycos upwards in the section may indicate that environment became less stressed, shallower and likely had a higher nutrient content or alternatively there was a change in the trace-maker biological affinity. The depositional environment shows some evidence of low-oxygenated to dysoxic conditions, because abundant Chondrites occurs without any other trace fossils with the exception of Zoophycos. Chondrites trace-makers likely maintained a connection to oxygenated water but penetrate into anoxic sediments rich in sulfides or ammonium that are required for microbe-breeding and feeding. Most likely studied Zoophycos-Chondrites and pure Zoophycos associations of the Upper Member of the Diatomaceous Formation are of deeper shelf origin. The diatomaceous volcanic ash beds of the upper part of the formation are intensively bioturbated by a horizontal network of large-size Thalassinoides, which represents domichnial and fodinichnial structures, and suggesting an enough oxygenated environment with sufficient nutrients. Thalassinoides level likely represents shallower water conditions (shallow shelf) than the underlying levels characterised with Zoophycos-Chondrites and Zoophycos associations.

中文翻译：

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来自阿尔及利亚西北部墨西拿（上中新世）的丰富动物藻类和球粒陨石

摘要 下切利夫盆地（NW-Algeria）广泛出露墨西拿硅藻矿床。硅藻组上部被四个富含动物藻类和球粒陨石的硅藻层夹层。这两种痕迹都是由适应沉积物中养分开发的底栖动物群的成员产生的。在硅藻组中，较大的深色球粒陨石横切较小的 C. intricatus，这可能表明生态演替可能是由于条件变得较少含氧并导致需要更大的洞穴。该部分中 Zoophycos 的大小增加可能表明环境压力变小、变浅并且可能具有更高的营养含量，或者示踪剂生物亲和力发生了变化。沉积环境显示出一些低氧至缺氧条件的证据，因为除了 Zoophycos 外，没有任何其他痕迹化石出现了丰富的球粒陨石。球粒陨石的示踪剂可能与含氧水保持联系，但会渗透到富含硫化物或铵的缺氧沉积物中，这些都是微生物繁殖和喂养所需的。最有可能研究的动物藻-球粒陨石和硅藻组上段的纯动物藻组合来自更深的陆架。地层上部的硅藻火山灰层受到大型海洋藻类水平网络的强烈生物扰动，代表着海洋和食肉结构，表明有足够的含氧环境和充足的养分。