title: Changing the picture of Earth's earliest fossils (3.5-1.9 Ga) with new approaches and new discoveries.
abstract: New analytical approaches and discoveries are demanding fresh thinking about the early fossil record. The 1.88-Ga Gunflint chert provides an important benchmark for the analysis of early fossil preservation. High-resolution analysis of Gunflintia shows that microtaphonomy can help to resolve long-standing paleobiological questions. Novel 3D nanoscale reconstructions of the most ancient complex fossil Eosphaera reveal features hitherto unmatched in any crown-group microbe. While Eosphaera may preserve a symbiotic consortium, a stronger conclusion is that multicellular morphospace was differently occupied in the Paleoproterozoic. The 3.46-Ga Apex chert provides a test bed for claims of biogenicity of cell-like structures. Mapping plus focused ion beam milling combined with transmission electron microscopy data demonstrate that microfossil-like taxa, including species of Archaeoscillatoriopsis and Primaevifilum, are pseudofossils formed from vermiform phyllosilicate grains during hydrothermal alteration events. The 3.43-Ga Strelley Pool Formation shows that plausible early fossil candidates are turning up in unexpected environmental settings. Our data reveal how cellular clusters of unexpectedly large coccoids and tubular sheath-like envelopes were trapped between sand grains and entombed within coatings of dripstone beach-rock silica cement. These fossils come from Earth's earliest known intertidal to supratidal shoreline deposit, accumulated under aerated but oxygen poor conditions.
authors.affiliation: Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom;
authors.forename: Martin D
authors.initials: MD
authors.lastname: Brasier
authors.affiliation: Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom; School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom;
authors.forename: Jonathan
authors.initials: J
authors.lastname: Antcliffe
authors.affiliation: Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, WA 6009, Australia; and.
authors.forename: Martin
authors.initials: M
authors.lastname: Saunders
authors.affiliation: Centre for Microscopy Characterisation and Analysis, The University of Western Australia, Crawley, WA 6009, Australia; and Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, The University of Western Australia, Crawley, WA 6009, Australia David.Wacey@bristol.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Wacey
mesh_terms: D018534:Earth, Planet; D004777:Environment; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry; D009864:Ontario; D010163:Paleontology / Q000379:methods*; D013997:Time Factors; D014904:Western Australia
keywords: astrobiology; biogeochemistry; early life; microfossils; paleontology