Ediacaran macrofossils prior to the ~580 Ma Gaskiers glaciation in Newfoundland, Canada ALEXANDER G. LIU AND BENJAMIN H. TINDAL Liu, A. G., & Tindal, B. H. 2020: Ediacaran macrofossils prior to the ~580 Ma Gaskiers glaciation in Newfoundland, Canada. Lethaia, https://doi.org/10.1111/let.12401. Macrofossils of the inferred protist‐grade organism Palaeopascichnus linearis occur stratigraphically beneath glacial diamictites of the ~580 Ma, Gaskiers‐equivalent, Trin- ity ‘facies’ of the Rocky Harbour Formation on the Bonavista Peninsula of Newfound- land, Canada. These fossils significantly pre‐date previously reported macrofossils from Avalonia and extend the taphonomic window for moldic preservation of macroscopic organisms beyond the Gaskiers glacial event into the middle Ediacaran Period. This finding confirms the long stratigraphical range of palaeopascichnid fossils worldwide and informs discussions surrounding both the age of poorly time‐constrained strati- graphical units in Norway and Australia, and formal sub‐division of the Ediacaran Sys- tem. □ Bonavista Peninsula, Ediacara biota, Palaeopascichnus, protist, stratigraphy. Alexander G. Liu ✉ [[email protected]], and Benjamin H. Tindal [[email protected]], Department of Earth Sciences, University of Cambridge, Downing Street Cambridge CB2 3EQ, UK; manuscript received on 10/04/2020; manuscript accepted on 26/07/2020. The island of Newfoundland in eastern Canada hosts 2011). Both of these units have been dated to ~580– several globally significant localities for late Edi- 579 million years (Bowring et al. 2003; Pu et al. acaran age fossils of the Ediacaran Macrobiota. Such 2016), and along with other glacial deposits of this localities record benthic palaeocommunities of age (e.g. the Mortensnes Formation of Finnmark, diverse soft‐bodied organisms and include Mistaken Norway; Rice et al. 2011) are considered to record an Point Ecological Reserve UNESCO World Heritage important regional glacial event: the Gaskiers glacia- Site and Spaniard's Bay on the Avalon Peninsula, tion (e.g. Halverson et al. 2005; Fairchild & Kennedy and the Catalina Dome (within the Discovery Global 2007). Iron speciation data from Newfoundland indi- Geopark) on the Bonavista Peninsula (Fig. 1B; Nar- cate at least local oxygenation of the deep ocean fol- bonne 2004; Narbonne in Fedonkin et al. 2007; Hof- lowing the Gaskiers glaciation (Canfield et al. 2007), mann et al. 2008; Liu & Matthews 2017). These fossil encouraging proposed links between the Gaskiers assemblages are dated to between ~574 and 562 Ma event and the evolution of diverse macroscopic com- (Canfield et al. 2020; Matthews et al. 2020) and lie plexity and large body size (as represented by the rise within siliciclastic strata deposited in deep‐marine to and diversification of the classic Ediacara‐type biota; marine‐slope settings (Wood et al. 2003). Over 30 e.g. Narbonne & Gehling 2003). However, such phys- distinct taxa have been described to date (Liu et al. iological links remain unproven at present (Sperling 2015), and in addition to non‐metazoan and prob- et al. 2015; Pu et al. 2016). lematic taxa, the assemblages include some of the Globally, the Lantian Formation of South China oldest reported body (e.g. Liu et al. 2014; Dunn et al. provides the most compelling evidence for complex 2018) and trace (Liu et al. 2010; Menon et al. 2013) macroscopic Ediacaran life prior to 580 Ma (Yuan fossil evidence for total group metazoans. Fossils of et al. 2011; Wan et al. 2016), but its precise age is yet the Ediacaran Macrobiota from Newfoundland rep- to be ascertained, and the vast majority of its taxa are resent some of the oldest known examples of the not observed in later Ediacaran fossil assemblages. classic Ediacara‐type biota anywhere in the world Older reports of complex macroscopic eukaryotes (alongside Charnwood Forest, England, and the remain contentious (e.g. El Albani et al. 2010), reflect Wernecke and Mackenzie Mountains of Canada; problematic taxa (Fedonkin & Yochelson 2002) or Noble et al. 2015; Rooney et al. 2020). comprise simple algal‐like (Ye et al. 2015; Zhu et al. All previously documented Ediacaran macrofossils 2016) or discoidal impressions (e.g. Burzynski et al. in Newfoundland stratigraphically and radiometri- 2020). cally post‐date glacigenic diamictites of the Gaskiers This study presents specimens of the probable Formation (Eyles & Eyles 1989), or its northern protozoan Palaeopascichnus linearis from marine equivalent on the Bonavista Peninsula, the Trinity strata within the Rocky Harbour Formation of New- ‘facies’ of the Rocky Harbour Formation (Normore foundland. These specimens demonstrably pre‐date DOI 10.1111/let.12401 © 2020 Lethaia published by John Wiley & Sons Ltd on behalf of Lethaia Foundation This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. 2 A. G. Liu and B. H. Tindal LETHAIA 10.1111/let.12401 Fig. 1. Map of the field locality and regional stratigraphical context. A, Newfoundland, Canada. B, the Avalon and Bonavista peninsulas, showing key Ediacaran fossil localities (orange), and the location of Trinity East area (yellow). C, towns of the Trinity area, showing the location of Trinity East, and the Freshwater Trestle (yellow star) and Herring Cove (green star) fossil localities. Inset: photograph of the logged section taken from across Freshwater Trestle. D, regional stratigraphy at formation scale (following Normore 2011). The radiomet- ric date originates from a volcanic horizon 11.1 m below the base of the Trinity ‘facies’ diamictite at Old Bonaventure (orange star in C; stated error indicates only internal [analytical] uncertainty, Pu et al. 2016). ~580 Ma diamictites of the Trinity ‘facies’ and there- logged at a 10‐cm resolution as part of an ongoing fore represent the oldest documented macrofossils study into Ediacaran glacial sedimentology in New- from the Ediacaran successions of Newfoundland. foundland. The stratigraphical and sedimentological discussions below draw upon observations made during that regional study, and are additionally Materials and methods informed by the findings of a team of six undergrad- uates from the University of Cambridge who mapped Fossil‐bearing horizons are situated on the western the wider region around the town of Trinity at shoreline of an inlet known locally as Freshwater 1:10,000 scale in the summer of 2018. Trestle, just a few hundred metres to the west of the town of Trinity East on the Bonavista Peninsula, Geological context Newfoundland (Fig. 1). Continuous exposure through the middle of the Rocky Harbour Formation Two distinct Ediacaran age stratigraphical succes- (Musgravetown Group) is observed along a disused sions on the Bonavista Peninsula are separated by railway cutting that runs parallel to the shoreline. the Spillars Cove–English Harbour fault (O'Brien & Fossil‐bearing surfaces from two discrete horizons King 2002, 2004; Normore 2011). To the east of the were sampled (Fig. 2), yielding 32 distinct fossil spec- fault lies the St. John's Basin, with a succession com- imens, which were studied in the laboratory. Studied prising shallowing‐upwards deep‐marine to fluvial specimens are accessioned in the collections of the units of the Conception, St. John's and Signal Hill Sedgwick Museum, University of Cambridge under Groups. The Conception and St. John's Groups host specimen numbers CAMSM X 50348.1 to CAMSM almost all previous reports of fossils of the Ediacaran X 50348.7 in Appendix S1. The sedimentary section Macrobiota in Newfoundland (e.g. Hofmann et al. along the western side of Freshwater Trestle was 2008; Mason et al. 2013; Liu et al. 2015). To the west, Fig. 2. Sedimentary log through the Rocky Harbour Formation section on the western shoreline of Freshwater Trestle, near Trinity East, Bonavista Peninsula, Newfoundland. Facies names to the right follow the lithostratigraphical nomenclature of Normore (2011), but their order in our section is not consistent across all other nearby sections (e.g. Supplementary Material of Pu et al. 2016). The two fossil hori- zons lie 7 and 35 m below the base of the Trinity ‘facies’. MISS = microbially induced sedimentary structures. LETHAIA 10.1111/let.12401 Pre‐Gaskiers Ediacaran macrofossils 3 4 A. G. Liu and B. H. Tindal LETHAIA 10.1111/let.12401 the Bonavista Basin hosts sedimentary rocks of the Bonaventure (Fig. 1C) indicate a short duration for Musgravetown Group, which reflect sedimentation deposition of the diamictite, contemporaneous in shallow marine depositional environments, within error with deposition of the Gaskiers Forma- beneath non‐marine sedimentary rocks of the Crown tion on the Avalon Peninsula (Pu et al. 2016, see dis- Hill Formation (O'Brien & King 2002; Normore cussion below). 2011). This western basin has not previously yielded reports of Ediacaran age macrofossils. Freshwater Trestle fossil locality The Rocky Harbour Formation lies within the Musgravetown Group and comprises siliciclastic and The studied section in Freshwater Trestle comprises volcanogenic lithologies that have been divided into approximately 200 m of largely continuous stratigra- seven mappable ‘facies’ by Normore (2011, following phy. Beds dip at 80–90° to the northeast. With the pos- O'Brien & King 2002, 2004, 2005) during regional sible exception of the base of the diamictite, the mapping for the Geological Survey of Newfoundland observed succession appears to be conformable