Traces of Early Life From the Barberton Greenstone Belt, South Africa

There is much convincing evidence for early life in the Barberton greenstone belt (3.47-3.22 Ga), portraying a diverse Paleoarchean biosphere that occupied both marine and terrestrial habitats. This stands testament to the already widespread distribution and diversity of life on the early Earth. We here present an up-to-date review of fifty years of accumulated evidence for life in the Barberton greenstone belt and outline the reasoning for biogenicity in each case. Fossils of microbial life are present throughout the stratigraphy, from the oldest chert unit (the Middle Marker horizon) to the uppermost siliciclastic sediments (the Moodies Group). Although phototrophs could also develop in nutrient poor, oligotrophic areas away from hydrothermal vents, chemotrophs appear to have been strongly controlled by proximity to hydrothermally derived nutrients. The Paleoarchean was a time of surprising biological diversity, and this record is best accessed by investigating the biomes preserved in chertified horizons.