Earth´s earliest mappable ecosystem

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The Barberton Greenstone Belt, South Africa, contains a very‐high‐resolution record of Middle Archaean (Moodies Group, ~3.2 Ga), dominantly nearshore depositional environments which preserve an extensive, morphologically diverse microbial biota. These biomats represent the oldest‐known well‐preserved mappable biomediated units; any older signs of life are either restricted to outcrop‐scale (or smaller) or show low morphological diversity (e.g., banded carbonaceous cherts). In addition, previous signs of microbial life are known only from carbonate, deep‐water or evaporitic environments.Micromorphology and extent of the biomats is facies‐dependent and adapted to medium‐ to high‐energy sandy and gravelly, mud‐free shorelines. Microbial mats are composed of isotopically light kerogen and show remnants of cellular structures; their internal complexity, metabolism and ecology is subject of this proposal. Abundant bulbous and domal structures suggest trapping of metabolic gases and possibly phototactic behavior. The great age, diverse morphology, abundance, mappable extent, fair degree of preservation and well‐defined paleoenvironments makes these mats an ideal object to study chemical composition, (micro‐)stratigraphic architecture and sedimentary facies. I believe that this proposal holds the potential to expand our knowledge of early life habitats on Earth and possibly elsewhere, constrain early metabolic pathways, and contribute to our knowledge of biologic diversification, early strategies of life and the rise of oxygen.