Preservation of early Tonian macroalgal fossils from the Dolores Creek Formation, Yukon ; Scientific Reports

The rise of eukaryotic macroalgae in the late Mesoproterozoic to early Neoproterozoic was a critical development in Earth's history that triggered dramatic changes in biogeochemical cycles and benthic habitats, ultimately resulting in ecosystems habitable to animals. However, evidence of the diversification and expansion of macroalgae is limited by a biased fossil record. Non-mineralizing organisms are rarely preserved, occurring only in exceptional environments that favor fossilization. Investigating the taphonomy of well-preserved macroalgae will aid in identifying these target environments, allowing ecological trends to be disentangled from taphonomic overprints. Here we describe the taphonomy of macroalgal fossils from the Tonian Dolores Creek Formation (ca. 950 Ma) of northwestern Canada (Yukon Territory) that preserves cm-scale macroalgae. Analytical microscopy, including scanning electron microscopy and tomographic x-ray microscopy, was used to investigate fossil preservation, which was the result of a combination of pyritization and aluminosilicification, similar to accessory mineralization observed in Paleozoic Burgess Shale-type fossils. These new Neoproterozoic fossils help to bridge a gap in the fossil record of early algae, offer a link between the fossil and molecular record, and provide new insights into evolution during the Tonian Period, when many eukaryotic lineages are predicted to have diversified. ; National Science and Engineering Research Council of Canada (NSERC); Geological Society of America Graduate Research Grant, Northern Scientific Training Program; Chemical and Physical Sciences Research Visit Program (University of Toronto Mississauga); National Science foundation (NSF) [IF 1636643]; NSF [1652351, RGPIN2017-04025]; Agouron Grants; NASA [80NSSC18K1086]; NSERC [RGPIN435402] ; Published version ; We acknowledge and thank the First Nation of Na-Cho Nyak Dun for permitting our field work on their traditional lands. We thank T. Selly for technical support. This research was supported by ...