Earth´s earliest mappable ecosystem

南非Barberton绿岩带包含一个非常高分辨率的中太古代（modies群，~3.2 Ga）记录，主要是近岸沉积环境，保存了广泛的、形态多样的微生物群。这些生物体代表了已知最古老的保存完好的可绘制的生物中介单位；任何较古老的生命迹象要么局限于露头规模（或更小），要么表现出较低的形态多样性（例如，带状碳质燧石）。此外，以前的微生物生命迹象只在碳酸盐、深水或蒸发环境中被发现。生物群落的微形态和范围与相有关，适应于中至高能量的沙质和砾石质、无泥的海岸线。微生物席由同位素较轻的干酪根组成，具有细胞结构的残余；它们内部的复杂性、新陈代谢和生态是本提案的主题。丰富的球根和穹窿结构暗示了代谢气体的捕获和可能的趋光行为。年龄大、形态多样、丰度高、可测绘范围广、保存程度好、古环境明确，使这些地垫成为研究化学成分、（微）地层结构和沉积相的理想对象。我相信这一提议有可能扩大我们对地球上以及其他地方早期生命栖息地的了解，限制早期代谢途径，并有助于我们了解生物多样化、生命早期策略和氧气的出现。

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.