Biogenic origin for Earth's oldest putative microfossils

Bradley T. De Gregorio, Thomas Sharp, George J. Flynn, Sue Wirick, Richard Hervig

Research output: Contribution to journalArticle

56 Scopus citations

Abstract

Carbonaceous microbe-like features preserved within a local chert unit of the 3.5 Ga old Apex Basalt in Western Australia may represent some of the oldest evidence of life on Earth. However, the biogenicity of these putative microfossils has been called into question, primarily because the sample collection locality is a black, carbon-rich, brecciated chert dike representing an Archean submarine hydrothermal spring, suggesting a formation via an abiotic organic synthesis mechanism. Here we describe the macromolecular hydrocarbon structure, carbon bonding, functional group chemistry, and biotic element abundance of carbonaceous matter associated with these filamentous features. These characteristics are similar to those of biogenic kerogen from the ca. 1.9 Ga old Gunflint Formation. Although an abiotic origin cannot be entirely ruled out, it is unlikely that known abiotic synthesis mechanisms could recreate both the structural and compositional complexity of this ancient carbonaceous matter. Thus, we find that a biogenic origin for this material is more likely, implying that the Apex microbe-like features represent authentic biogenic organic matter.

Original languageEnglish (US)
Pages (from-to)631-634
Number of pages4
JournalGeology
Volume37
Issue number7
DOIs
StatePublished - Sep 8 2009

ASJC Scopus subject areas

  • Geology

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