Diverse vase-shaped microfossils within a Cryogenian glacial setting in the Urucum Formation (Brazil)

Vase-shaped microfossils (VSMs) attributed to testate amoebae occur globally in diverse assemblages Tonian rocks. These have thus been considered a potential biostratigraphic tool, especially for the interval between 789 and 729 Ma. Here we report well-preserved situ VSM assemblage, including several taxa previously as Tonian, within glacially influenced deposits which sedimentological data support Cryogenian age. However, more robust recent multi-proxy correlation proposed by Freitas et al. (2021) indicates Marinoan age studied succession. Detrital zircon provide maximum depositional weighted mean of 749 ± 3 Ma VSM-bearing, organic-rich, fine-grained sequence Urucum Formation. Nine are described from upper Formation, Jacadigo Group, Brazil: Cycliocyrillium simplex, Bonniea dacruchares, pytinaia, Bombycion micron, Limeta lageniformis, Palaeoarcella athanata, Trigonocyrillium horodyskii, Pakupaku kabin cf. Taruma rata. The discovery VSMs attributable specific succession challenges previous thinking that these organisms disappeared marine ecosystems at end Tonian.