Ichnological aspects of the Aquidauana Formation (Upper Carboniferous, Itararé Group, Brazil): An arthropod-colonized glacial setting

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2021-09, Vol.578, p.110575, Article 110575
• Main Authors: de Barros, Gabriel E.B., Becker-Kerber, Bruno, Sedorko, Daniel, Lima, João Henrique Dobler, Pacheco, Mírian L.A.F.
• Format: Article
• Language: English
• Subjects: Glacial freshwater environment; Ichnodisparity; Ichnotaxonomy; New Ichnomorphotypes; Trace fossils
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2021.110575

The Late Paleozoic Ice Age (LPIA) in Brazil has an extended sedimentary record, mainly in the Paraná Basin. Ichnological records are the main biotic evidence in such an environment, and the Itararé Group (Paraná Basin) is important in this regard. However, the Aquidauana Formation, one of the formations in the Itararé Group, is understudied regarding its trace fossil record. Thus, here we present the first ichnotaxonomic characterization of the Aquidauana Formation. We identified ten ichnospecies: Cruziana problematica, Cruziana cf. carbonaria, Diplichnites gouldi, Diplopodichnus biformis, Helmintoidichnites tenuis, cf. Kouphichnium isp., Monomorphichnus lineatus, Rusophycus carbonarius, Umfolozia sinuosa, and Warvichnium ulbrichi. Moreover, we also observed the presence of different morphotypes distributed among two ichnogenera: Monomorphichnus and Warvichnium. We also identified microbially induced sedimentary structures (Arumberia). According to these results, the paleoichnocoenosis of the Aquidauana Formation is characterized by the dominance of activity of small arthropods (probably benthic crustaceans), presenting a low richness of functional morphology. This depauperate ichnocoenosis may reflect environmental stress related to glacial environments and short colonization periods, corroborated by the absence of mixed-layer activity. Compared to other Gondwanic glacial deposits, the Aquidauana Formation is unique to present Warvichnium and Monomorphichnus. This unit also reveals a relationship with freshwater influence, similar to the Mafra Formation fjords in the southern Paraná Basin. Thus, the Aquidauana Formation represents invertebrate colonization of submerged glacial freshwater environments in Gondwana, followed by subaerial exposure. [Display omitted] •First ichnotaxonomic characterization of the Aquidauana Formation•Record of arthropod and wormlike trace fossils•Record of Arumberiamorph structures and Warvichnium in Upper Paleozoic deposits•New morphotypes for Monomorphichnus and Warvichnium•Low ichnodiversity and ichnodisparity with absence of an mixed-layer activity